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1
Bass, Sarah J. "Ambient noise in the surf zone". Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1995. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp04/mq25821.pdf.
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Shaw, Ronald R. "Ambient noise characteristics during the Sheba experiment". Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 2000. http://handle.dtic.mil/100.2/ADA378686.
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Thesis (M.S. in Meteorology and Physical Oceanography) Naval Postgraduate School, March 2000.Thesis advisor, Robert H. Bourke. Includes bibliographical references (p. 95-97). Also available online.
3
Arogundade, Simisola M. "Numerical modeling of ambient noise seismic interferometry". Thesis, Michigan Technological University, 2016. http://pqdtopen.proquest.com/#viewpdf?dispub=10125274.
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CO2 sequestration involves storing CO2 in a deep geological formation and may help to mitigate the increasing emission of carbon. To monitor the migration of injected fluid in the reservoir, seismic observations may be used to observe changes in reflection character. Conventional methods to image the subsurface, using active seismic measurements, with man-made sources, have been applied at a few test sites, and the use of passive measurements, with natural sources, has been considered as a probable cost-efficient method to monitor CO2 migration and leakage. This numerical modeling study examines the use of seismic interferometry to retrieve weak seismic reflections from background noise, a form of passive monitoring.
The factors that influence the quality of the retrieved reflections from interferometry include geophone interval, geophone depth, and effect of shallow noise sources, assuming we seek reflections from deep noise sources, representing either teleseismic events or local events as expected in a field of active injection. Using model data, geophone interval had no significant effect on the reflection quality, but buried geophones produce ghost reflections, suggesting that shallow geophones might be optimal. Shallow noise sources produce a destructive effect on the reflections from deeper noise sources and damage the resulting image.
4
Lani, Shane W. "Passive acoustic imaging and monitoring using ambient noise". Thesis, Georgia Institute of Technology, 2012. http://hdl.handle.net/1853/50136.
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An approximate of the Green's function can be obtained by taking the cross-correlation of ambient noise that has been simultaneously recorded on separate sensors. This method is applied for two experiments, which illustrate the advantages and challenges of this technique. The first experiment is in the ultrasonic regime [5-30] MHz and uses capacitive micromachined ultrasonic transducer arrays to image the near field and compares the passive imaging to the conventional pulse-echo imaging. Both the array and target are immersed in a fluid with the sensors recording the fluid's random thermal-mechanical motion as the ambient noise. The second experiment is a passive ocean monitoring experiment, which uses spatiotemporal filtering to rapidly extract coherent arrivals between two vertical line arrays. In this case the ambient noise in the frequency band [250 1500] Hz is dominated by non-stationary shipping noise. For imaging purposes, the cross-correlation needs to extract the Green's function so that the imaging can be done correctly. While for monitoring purposes, the important feature is the change in arrivals, which corresponds to the environment changing. Results of both experiments are presented along with the advantages of this passive method over the more accepted active methods.
5
Gray, Timothy D. "Analysis and simulation of ambient noise time series". Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp03/MQ57288.pdf.
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Bolin, Karl. "Masking of wind turbine sound by ambient noise". Licentiate thesis, Stockholm : Marcus Wallenberg laboratory for sound and vibration research, 2006. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-4227.
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Cousins, John David. "CEAREX ambient noise data measured northeast of Svalbard". Thesis, Monterey, California. Naval Postgraduate School, 1991. http://hdl.handle.net/10945/28023.
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Epifanio, Chad Lawrence. "Acoustic daylight : passive acoustic imaging using ambient noise /". Diss., Connect to a 24 p. preview or request complete full text in PDF format. Access restricted to UC campuses, 1997. http://wwwlib.umi.com/cr/ucsd/fullcit?p9823704.
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Legovini, Paride <1983>. "Ambient seismic noise tomography of the Antarctic continent". Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2019. http://amsdottorato.unibo.it/9023/1/tesi-legovini.pdf.
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The lithosphere of Antarctica reacts to both the stress variations due to the dynamics of the mantle and the variation of the glacial load due to changes in climate. These two factors act on the dynamics of the glacial mass, on the evolution of the continent's topography and on the plate seismicity. This means that the knowledge of spatial variations in lithospheric thickness is needed to comprehend of the processes that involve interactions between climate and the geosphere. The main aim of this work is to produce a tomographic model of the continent.
The classic data source for tomographic studies is a set of seismic signals produced by earthquakes. In this work I use a different technique: information is extracted by correlating the ambient seismic noise recorded in different locations. Instead of a the classic cross-correlation, this work uses the phase cross correlation technique, which appears to be more robust in our use case. Signal phases are used even to improve the correlogram stacks, by weighting the stack samples according to the correlograms' coherence.
In Antarctica, the 30s Rayleigh wave group velocity map shows lower velocities in East Antarctica, and higher velocities in West Antarctica, coherently with expectations related to a thicker cratonic crust in the East, and thinner extending crust in the West. Deeper sensitivity of longer periods make the color pattern switch for the 80s map, sensing the upper mantle and consequently higher velocity at the cold roots of cratonic East Antarctica and lower velocity in the tectonically active West.
I also contributed to the maintenance and development of the seismic observational infrastructure in Antarctica. This thesis recaps the activities I carried out during my participation to the 31st campaign of the Italian National Antarctic Research Program, to which I participated during the PhD course.
10
Kedhammar, Anders. "Auditory masking of wind turbine noise with ambient sounds". Thesis, Stockholm University, Department of Psychology, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-37438.
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The expansion of wind energy production creates an increase in wind turbine (WT) noise. The purpose of this paper is to examine if a possible reduction of WT noise might be achieved by adding natural ambient sounds, so called auditory masking. A loudness experiment was conducted to explore this possibility, using four ambient sounds of trees, birds and water as maskers. Sixteen listeners assessed the loudness of WT noise heard alone or in the presence of 40 dB masking sounds, using the method of magnitude estimation. Partial masking of WT noise was found in the presence of all ambient sounds. The masking effect corresponded to a dB-reduction of the WT noise from a few dB for signal-to-noise ratios (S/N) close to 0 dB up to around 10 dB at -15 dB S/N. These results indicate that addition of ambient sounds may be a useful method for masking unwanted noise from wind turbines.
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Chernets, Olga. "The estimation of Arctic ice thickness from ambient noise". Thesis, Massachusetts Institute of Technology, 1995. http://hdl.handle.net/1721.1/38188.
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Vawter, Noah (Noah Theodore). "Ambient addition : how to turn urban noise into music". Thesis, Massachusetts Institute of Technology, 2006. http://hdl.handle.net/1721.1/36161.
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Thesis (S.M.)--Massachusetts Institute of Technology, School of Architecture and Planning, Program in Media Arts and Sciences, 2006.Includes bibliographical references (leaves 99-103).
As human civilization devises ever more powerful machines, living among them may become more difficult. We may find ourselves surrounded by incidentally created sounds and noises which are out of synchronization with our momentary needs and discordant. Currently, legislating noise pollution is the only articulated solution and clearly it is not very effective. Our impression of sound, however, may be mediated and manipulated, transformed into something less jarring. So far, Walkmans and sound canceling headphones have done this, isolating us from noise but also from one another. In their place, a next generation headphone system is proposed which integrates environmental sound into a personal soundscape. It allows one to synthesize music from environmental sound using a number of digital signal processing (DSP) algorithms to create a sonic space in which the listener remains connected with his or her surroundings, is also cushioned from the most harsh and arrhythmic incursions and may also be drawn to appreciate the more subtle and elegant ones.
by Noah Vawter.
S.M.
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Felizardo, Francis Camomot. "Ambient noise and surface wave dissipation in the ocean". Thesis, Massachusetts Institute of Technology, 1993. http://hdl.handle.net/1721.1/12460.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 1993.Includes bibliographical references (leaves 189-201).
by Francis C. Felizardo.
Ph.D.
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Allmark, Claire Lindsay. "Analysing the Earth's near surface using ambient seismic noise". Thesis, University of Edinburgh, 2018. http://hdl.handle.net/1842/29639.
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Near surface measurements of seismic velocity and Q are useful in a number of situations, for example for when carrying out re-datuming and migration for depth images, or when analysing ground conditions for building. This thesis concentrates on the estimation of surface wave group and phase velocity as well as Q structure through the use of cross correlations of ambient noise recordings. Linearised tomography estimates are made for the British Isles, the Permain Basin of Texas and New Mexico, the Ekofisk Life of Field Seismic (LoFS) array and the Aquistore CO2 storage site. The results correspond well with the known geological structure and/or structure observed in velocity maps by other researchers. For the Ekofisk array a non-linearised non-linear method was also applied and the results estimated by these two methods for the Ekofisk LoFS array are compared. By non-linearised non-linear it is meant that the inversion method is fully non-linear and no linearisation has taken place in the method, this term will be used throughout this thesis for all methods which fall into this category. The tomography results from the two methods had similarities in their general structure but differences in the finer details, and so suggest that the substantial increase in time required for the non-linearised non-linear method is not justified. Linearised tomographic inversion of the Aquistore array was used to determine the potential of using ambient noise tomography for monitoring of CO2 storage sites. It was found that the repeatability of the tomography at the Aquistore site was not good enough to allow ambient noise tomography to be used for monitoring; however, it may be possible to apply the method at other sites. A Q and phase velocity inversion of the Ekofisk array is also presented, with results mostly showing excellent correlation with known geological features. It is shown that the higher frequencies are more sensitive to the effects of sea floor subsidence at the site, while lower frequencies are more sensitive to the effects of faulting. A final near surface method called ambient noise gradiometry was applied, this concentrates on estimating locations of sources of seismic energy within receiver arrays. Ambient noise gradiometry is applied to synthetic and real data for this purpose. It was found that using ambient noise gradiometry allows internal sources of energy to be identified but they produce a bias in the phase velocity tomography result. Two methods of reducing this bias are presented, both of which also provide an estimate of the source term for different sections of time of the recording.
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AlMuhanna, Khalid A. "Acoustic modeshape inversion using deep water ambient noise measurements". Fairfax, VA : George Mason University, 2008. http://hdl.handle.net/1920/3214.
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Thesis (M.S.)--George Mason University, 2008.Vita: p. 69. Thesis director: Kathleen E. Wage. Submitted in partial fulfillment of the requirements for the degree of Master of Science in Electrical Engineering. Title from PDF t.p. (viewed Aug. 27, 2008). Includes bibliographical references (p. 67-68). Also issued in print.
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Andronis, Nicholas. "Reliable Long-Range and High Ambient Noise Underwater Communication". Thesis, Curtin University, 2019. http://hdl.handle.net/20.500.11937/76485.
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Long-Range and high ambient noise underwater communication reliability improvement via sea trail performance validation of whole-of-system algorithm and engineering optimisations. The resulting 10 dB performance improvement can be used to increase the transmit source level by up to 10 dB, extend communication range by 50%, operate in environments with up to 10 dB louder ambient noise, reduce hydro-acoustic noise pollution or lowering battery power consumption with the potential of ocean powered networked communication.
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Powell, Jason W. "Predictive Modeling for Persuasive Ambient Technology". Thesis, University of North Texas, 2015. https://digital.library.unt.edu/ark:/67531/metadc804947/.
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Computer scientists are increasingly aware of the power of ubiquitous computing systems that can display information in and about the user's environment. One sub category of ubiquitous computing is persuasive ambient information systems that involve an informative display transitioning between the periphery and center of attention. The goal of this ambient technology is to produce a behavior change, implying that a display must be informative, unobtrusive, and persuasive. While a significant body of research exists on ambient technology, previous research has not fully explored the different measures to identify behavior change, evaluation techniques for linking design characteristics to visual effectiveness, nor the use of short-term goals to affect long-term behavior change. This study uses the unique context of noise-induced hearing loss (NIHL) among collegiate musicians to explore these issues through developing the MIHL Reduction Feedback System that collects real-time data, translates it into visuals for music classrooms, provides predictive outcomes for goalsetting persuasion, and provides statistical measures of behavior change.
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Leroy, Charlotte. "Using ocean ambient noise cross-correlations for passive acoustic tomography". Thesis, Georgia Institute of Technology, 2011. http://hdl.handle.net/1853/39636.
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Recent theoretical and experimental studies have demonstrated that an estimate of the Green's function between two hydrophones can be extracted passively from the cross‐correlation of ambient noise recorded at these two points. Hence monitoring the temporal evolution of these estimated Green's functions can provide a means for noise‐based acoustic tomography using a distributed sensor network. However, obtaining unbiased Green's function estimate requires a sufficiently spatially and temporally diffuse ambient noise field. Broadband ambient noise ([200 Hz-20 kHz]) was recorded continuously for 2 days during the SWAMSI09 experiment (next to Panama City, FL) using two moored vertical line arrays (VLAs) spanning 7.5m of the 20‐m water column and separated by 150 m. The feasibility of noise‐based acoustic tomography ([300-1000 Hz]) was assessed in this dynamic coastal environment over the whole recording period. Furthermore, coherent array processing of the computed ocean noise cross‐correlations between all pairwise combinations of hydrophones was used to separate acoustic variations between the VLAs caused by genuine environmental fluctuations-such as internal waves-from the apparent variations in the same coherent arrivals caused when the ambient noise field becomes strongly directional, e.g., due to an isolated ship passing in the vicinity of the VLAs.
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Woolfe, Katherine F. "Passive acoustic monitoring of the deep ocean using ambient noise". Diss., Georgia Institute of Technology, 2015. http://hdl.handle.net/1853/53910.
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In the ocean, changes in the speed of sound can be related to changes in water temperature. By leveraging this relationship, acoustic methods – namely acoustic tomography- have been used to monitor temperature changes in the deep ocean for the purposes of providing inputs to climate change models. Traditionally, these acoustic methods involve loud, active sound sources which can be logistically challenging to operate and have been criticized for potentially disturbing marine animals. Therefore, this work demonstrates a passive acoustic method - previously only used in shallow water for short monitoring durations- that uses only recordings of low-frequency (1-40 Hz) ambient noise to continuously monitor variations in deep ocean temperature with an unprecedented degree of precision and temporal resolution. Numerical simulations were conducted to show the portions of the ocean that are monitored with this passive method. This work also provides recommendations (regarding sensor placement around the world) for future development of a global passive acoustic sensor network that makes use of distant noise sources (sea-ice or seismic sources) to extract meaningful information (whether temperature, currents, etc.) about the ocean. Finally, an optimization method is proposed to overcome one of the fundamental limitations of previous applications of this passive monitoring method: tracking oceanic fluctuations that occur over short time scales. Hence, the results of this study may assist in the development of more reliable climate models that include an enhanced understanding of the ocean’s role as a global heat sink. Finally, an optimization method was proposed to enhance the emergence rate of coherent arrivals from ambient noise correlations, thus allowing this passive monitoring method to track acoustic medium fluctuations on a shorter time scale. This optimization could also be used in other applications of noise-based passive monitoring in a rapidly fluctuating medium (seismic, structural health monitoring, biomedical, etc.).
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Snyder, Mark Alan. "Long-Term Ambient Noise Statistics in the Gulf of Mexico". ScholarWorks@UNO, 2007. http://scholarworks.uno.edu/td/595.
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Long-term omni-directional ambient noise was collected at several sites in the Gulf of Mexico during 2004 and 2005. The Naval Oceanographic Office deployed bottom moored Environmental Acoustic Recording System (EARS) buoys approximately 159 nautical miles south of Panama City, Florida, in water depths of 3200 meters. The hydrophone of each buoy was 265 meters above the bottom. The data duration ranged from 10-14 months. The buoys were located near a major shipping lane, with an estimated 1.5 to 4.5 ships per day passing nearby. The data were sampled at 2500 Hz and have a bandwidth of 10-1000 Hz. Data are processed in eight 1/3-octave frequency bands, centered from 25 to 950 Hz, and monthly values of the following statistical quantities are computed from the resulting eight time series of noise spectral level: mean, median, standard deviation, skewness, kurtosis and coherence time. Four hurricanes were recorded during the summer of 2004 and they have a major impact on all of the noise statistics. Noise levels at higher frequencies (400-950 Hz) peak during extremely windy months (summer hurricanes and winter storms). Standard deviation is least in the region 100-200 Hz but increases at higher frequencies, especially during periods of high wind variability (summer hurricanes). Skewness is positive from 25-400 Hz and negative from 630-950 Hz. Skewness and kurtosis are greatest near 100 Hz. Coherence time is low in shipping bands and high in weather bands, and it peaks during hurricanes. The noise coherence is also analyzed. The 14-month time series in each 1/3- octave band is highly correlated with other 1/3-octave band time series ranging from 2 octaves below to 2 octaves above the band's center frequency. Spatial coherence between hydrophones is also analyzed for hydrophone separations of 2.29, 2.56 and 4.84 km over a 10-month period. The noise field is highly coherent out to the maximum distance studied, 4.84 km. Additionally, fluctuations of each time series are analyzed to determine time scales of greatest variability. The 14-month data show clearly that variability occurs primarily over three time scales: 7-22 hours (shipping-related), 56-282 hours (2-12 days, weather-related) and over an 8-12 month period.
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Neale, Jennifer F. Ward. "An investigation into ocean wave sources of ambient seismic noise". Thesis, University of Southampton, 2017. https://eprints.soton.ac.uk/412555/.
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Periodic pressure fluctuations beneath ocean waves deform the seabed beneath them and can generate seismic waves that propagate around the globe. These pressure fluctuations are recorded on seafloor pressure gauges and the associated ground displacements on seismometers, where they contribute to ambient seismic noise. The signals offer an opportunity to study or monitor ocean waves that are traditionally difficult to measure because of their low wave heights (deep water infragravity waves) or their remote locations (deep water swell waves). However, the link between ocean waves and the oscillations of the pressure and seismic wavefields has remained unclear. The aim of this thesis was to increase our understanding of ocean sources of ambient seismic noise, including their location, how well they can be located, and their relationship with ocean wave parameters. Using cross-correlated pairs of seafloor pressure records, infragravity waves offshore California/Oregon were found to originate mostly from local coastlines during northern-hemisphere winter and from the south during summer. A first attempt to estimate the coastal reflection coefficient of remote arrivals was made and found to be 0.49-0.74, which has implications for infragravity energy in the deep ocean and may be important for models in which infragravity waves are propagated across ocean basins. P-wave sources in the North Pacific during winter were located using seismometers in California and found to be concentrated around 40-50◦N 160-180◦E. Observed source locations were within 10◦ of the modelled source locations. Significant wave height in the deep ocean was estimated from P-waves and correlated with modelled wave height with a correlation coefficient of 0.63. Previous work only attempted to estimate coastal wave heights. Combining additional records from Japan and Europe improved source location, including imaging of multiple sources. Accuracy in source location and amplitude estimation are essential if microseisms are to be used to monitor wave activity in the deep ocean.
22
Fang, Lihua. "Rayleigh wave tomography in North-China from ambient seismic noise". Doctoral thesis, Università degli studi di Trieste, 2010. http://hdl.handle.net/10077/3623.
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2008/2009The theory and methodology of ambient noise tomography has been studied and applied to North-China successfully. Continuous vertical-component seismograms, spanning the period from January 1, 2007 to February 28, 2008 recorded by 190 broadband stations and 10 very broadband stations, have been used. The cross correlation technique has been applied to ambient noise data recorded by North-China Seismic Array for each station pairs of the array. Rayleigh wave group velocity dispersion curves are measured at periods between 4 s and 40 s by multiple filter technique. We obtain 5630 high quality dispersion curves. Surface wave tomography is conducted to generate group velocity maps with a grid spacing of 0.25º×0.25º. These maps display higher resolution and extend to shorter periods than previous surface wave tomography maps. Then genetic algorithm is used to invert pure path dispersion curves. The 3-D shear wave velocity structure from 0 to 50 km depth is readily constructed. To the authors' knowledge, the resolution presented here is, so far, the highest one in China mainland. The original results of this thesis are: 1, The SNR of Green Function is proportional to the square root of observation time and can be enhanced by using the symmetric component. The inhomogeneous distribution of seismic noise gives rise to the asymmetry of Green Function. Using more than one year's data, one can get more symmetric and higher SNR Green Function. 2, The characteristics of ambient seismic noise are different for different period bands. In 4-10 s, a coherent phase with large amplitude near zero lag time is observed. In 10-20 s, the sources of ambient seismic noise have a very clear seasonal variability. The azimuthal distributions of noise share a great similarity with the map of average ocean wave height map obtained by TOPEX-Poseidon. In 20-50s range, Rayleigh wave Green Functions are almost symmetrical and show less seasonal variation in both signal strength and directivity, which indicates that the distribution of noise is - ii - almost homogeneous. In 4-20s range, the amplitudes of positive and negative components of Green Functions are obviously asymmetrical, but the arrival times are almost identical, indicating that the distribution of noise has much influence on the amplitude of Green Function, but less influence on arrival time. 3, Tomographic maps at short periods reveal an evident lateral heterogeneity in the curst of North-China, quite well in agreement with known geological and tectonic features. The North China Basin is imaged as a broad low velocity area, while the Taihangshan and Yanshan uplifts and Ordos block are imaged as high velocity zones, and the Quaternary intermountain basins show up as small low-velocity anomalies. 4, The 3-D S-wave crustal velocity model in North China shows a distinct low velocity belt with NW trend at 10 km of depth near Zhangjiakou-Bohai seismic zone. This low velocity belt and the southern margin of Yanshan high velocity anomaly draw the outline of Zhangjiakou-Bohai seismic zone and its northern border line. There is a well-defined low velocity zone in middle-to-lower crust (15-25 km) in the Beijing-Tianjin-Tangshan region, which may be caused by intrusion of hot mantle materials. 5, We analyzed the seismogenic structure near Tangshan，Luanxian and Ninghe earthquake region. We infer that these three earthquakes are mainly caused by vertical deformation of upper mantle and material exchange between crust and upper mantle. The magma intrudes the crust along faults near the boundary of crust and upper mantle, which leads to the low velocity anomaly in the uppermost mantle. The magma intrusion heats up the lower crustal material and drops its viscosity. Some minerals are dehydrated. The water moves up and is trapped in the middle crust. The existence of liquid affects the structure and composition of the fault zone, further changes the stress state, weakens the seismotectonic region and triggers the earthquakes.
XXI Ciclo
1981
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Cosgrove, Marianne S. "PERCEIVED IMPACT OF AMBIENT OPERATING ROOM NOISE BY CERTIFIED REGISTERED NURSE ANESTHETISTS". VCU Scholars Compass, 2019. https://scholarscompass.vcu.edu/etd/5963.
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It is widely acknowledged that elevated levels of noise are commonplace in the healthcare environment, particularly in high acuity areas such as the operating room (OR). Excessive ambient noise may pose a threat to patient safety by adversely impacting provider performance and interfering with communication among perioperative care team members. With respect to the certified registered nurse anesthetist (CRNA), increased ambient OR noise may engender distractibility, diminish situation awareness and cause untoward health effects, thereby increasing the possibility for the occurrence of error and patient injury.
This research project analytically examines the perceived impact of ambient noise in the operating room by CRNAs. Findings from this study reveal that CRNAs perceive elevated noise to be regularly present in the OR, specifically during the critical emergence phase of the anesthetic. However, CRNAs feel that increased noise only occasionally limits their ability to perform procedures, concentrate and communicate with the perioperative team. OR noise rarely interferes with memory retrieval. CRNAs perceive that noise is sometimes a threat to patient safety but infrequently engenders adverse patient outcomes. CRNAs do not perceive noise in the OR to be detrimental to their health but strongly agree that excessive noise can and should be controlled.
Increased ambient OR noise is a veritable reality that may pose a potential threat to patient safety. Further research to identify elevations in noise during critical phases of the anesthetic and delineation of significant contributors to its genesis is warranted.
24
Lovelace, Ronald M. "Comparison of narrow band and one third octave ambient noise measurements". Thesis, Monterey, California. Naval Postgraduate School, 1985. http://hdl.handle.net/10945/21202.
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Yao, Huajian. "Ambient noise interferometry and surface-wave array tomography in southeastern Tibet". Thesis, Massachusetts Institute of Technology, 2009. http://hdl.handle.net/1721.1/53115.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 2009.Includes bibliographical references.
The primary goal of my doctoral research is to understand the crustal and upper mantle structure and deformation in southeastern Tibet. To improve the resolution in the crust, we developed a new approach for surface-wave array tomography by combining inter-station phase velocity dispersion measurements from empirical Green's functions (EGFs) recovered from ambient noise interferometry and from traditional teleseismic surface-wave two-station (TS) analysis. The non-stationarity (e.g., seasonal changes) and non-uniform distribution of ambient noise sources may obstruct full reconstruction of the surface-wave Green's functions, which may, in turn, degrade the accuracy of the tomographic models. Under the assumption of plane-wave propagation, we developed an iterative method to estimate ambient noise energy distribution, phase velocity bias primarily due to uneven noise energy distribution, and azimuthally anisotropic phase velocity maps. With phase velocity dispersion measurements at periods 10 - 150 s from 1 year data of 75 broad band stations in SE Tibet, we performed inversion for wavespeed variations and azimuthal anisotropy. The tomographic images revealed widespread crustal low-velocity zones (LVZs) at middle/lower crustal depth beneath SE Tibet. There is substantial lateral and vertical variability of these zones and some may be truncated by large faults.
(cont.) The pattern of azimuthal anisotropy in the upper crust is consistent with clockwise rotation around the eastern Himalaya syntaxis and a predominance of simple shear and strike-slip faulting in SE Tibet. Comparison of splitting from SKS observations and from our 3D anisotropic model suggests that the contribution to splitting from the crust is at least as important as from the upper mantle in the region west of Sichuan Basin and north of 26°N. However, beneath Yunnan, splitting signal originates mainly from the upper mantle. The radial changes in deformation pattern argue against vertically coherent lithospheric deformation in Tibet. Combined with the widespread crustal LVZs, this supports models of ductile crustal flow beneath SE Tibet. However, the spatial variation in strength and depth of crustal LVZs and in pattern of azimuthal anisotropy suggests that the 3-D geometry of crustal weak layers is complex and that unhindered crustal flow over large regions may not occur.
by Huajian Yao.
Ph.D.
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Olivier, Gerrit. "Seismic imaging and monitoring in mines with ambient seismic noise correlations". Thesis, Université Grenoble Alpes (ComUE), 2015. http://www.theses.fr/2015GREAU018/document.
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Cette thèse s'intéresse au développement des méthodes d'auscultation sismique passive pour l'imagerie et la surveillance des mines profondes. Les résultats marquants sont 1/ la possibilité d'imager en profondeur les structures géologiques d'intérêt et 2/ la possibilité de suivre dans le temps les propriétés mécaniques des roches qui subissent les sollicitation associés à l'exploitation minière. Ce travail ouvre des perspectives quant à l'amélioration de la sécurité dans les mines profondesThis work focus on using passive noise-based seismic methods to image and monitor the rock mass in underground mines. The main results show that it is possible to gain benefit from the diffuse ambient seismic field in mines to 1/ image the rock mass and 2/ monitor its mechanical property changes over time. This work opens a way to improve safety in deep underground mines
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Stewart, Marc S. "Shallow water ambient noise caused by breaking waves in the surf zone". Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 1994. http://handle.dtic.mil/100.2/ADA293240.
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Thesis (M.S. in Applied Physics) Naval Postgraduate School, December 1994."December 1994." Thesis advisor(s): James H. Wilson, Robert H. Bourke, O.B. Wilson. Bibliography: p. 77-80. Also available online.
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Luo, Jinhong [Verfasser]. "Bats and ambient noise : From chatty neighbours to disturbing humans / Jinhong Luo". Konstanz : Bibliothek der Universität Konstanz, 2015. http://d-nb.info/1139640828/34.
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Arosio, Lucia. "Seismic ambient noise tomography of central Italy using a deep learning algorithm". Master's thesis, Alma Mater Studiorum - Università di Bologna, 2022. http://amslaurea.unibo.it/25637/.
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This work aims at testing a convolutional neural network (CNN), developed by Zhang et al. (2020), to measure group velocity of Rayleigh waves, extracted from records of background seismic noise, and at studying the crustal structure of Central Italy.
I investigate an area in Central Italy by means of seismograms recorded by 73 seismic stations located approximately in the Central and Northern Apennines. The study is part of a larger project, named MUSE (Multiparametric and mUltiscale Study of Earthquake preparatory phase), that has the goal, among others, of detecting the spatial and temporal evolution of the velocity in the Earth’s crust. In this context, I have obtained the group velocity maps representative of the entire time span, from 01/01/2010 to 01/05/2021.
In this study, I employ the technique of seismic ambient noise interferometry to extract Rayleigh wave measurements from the fully diffuse wavefields (Shapiro and Campillo, 2004). I then use CNN and other methods to determine the dispersion characteristics of the Rayleigh wave fundamental mode: a traditional method, requiring operator interaction; a classical automated procedure; and the recent neural network. I then invert each of the three dispersion data sets retrieved with the different approaches, to compute group velocity maps at different periods. I compare the performance of the different methods employed, and thus evaluate the performance of the CNN network, by comparing the maps among them, with geological observations, and also with a pre-existing model from the literature (Molinari et al., 2015).
The CNN method shows excellent potential, but – at the current stage of development – it needs more accurate and specific training to reach the precision of manual picks. My maps image the crustal structure of the Northern Apennines area with unprecedented detail. This work poses the basis for further studies, to image the time variations of 3D structure (i.e., 4D tomography).
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Sadeghisorkhani, Hamzeh. "Analyses and Application of Ambient Seismic Noise in Sweden : Source, Interferometry, Tomography". Doctoral thesis, Uppsala universitet, Geofysik, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-320169.
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Ambient seismic noise from generation to its application for determination of sub-surface velocity structures is analyzed using continuous data recordings from the Swedish National Seismic Network (SNSN). The fundamental aim of the thesis is to investigate the applicability of precise velocity measurements from ambient noise data. In the ambient noise method, a form of interferometry, the seismic signal is constructed from long-term cross correlation of a random noise field. Anisotropy of the source distribution causes apparent time shifts (velocity bias) in the interferometric signals. The velocity bias can be important for the study area (Sweden) which has relatively small velocity variations. This work explores the entire data path, from investigating the noise-source distribution to a tomographic study of southern Sweden. A new method to invert for the azimuthal source distribution from cross-correlation envelopes is introduced. The method provides quantitative estimates of the azimuthal source distribution which can be used for detailed studies of source generation processes. An advantage of the method is that it uses few stations to constrain azimuthal source distributions. The results show that the source distribution is inhomogeneous, with sources concentrated along the western coast of Norway. This leads to an anisotropic noise field, especially for the secondary microseisms. The primary microseismic energy comes mainly from the northeast. The deduced azimuthal source distributions are used to study the level of expected bias invelocity estimates within the SNSN. The results indicate that the phase-velocity bias is less than 1% for most station pairs but can be larger for small values of the ratio of inter-station distance over wavelength. In addition, the nature of velocity bias due to a heterogeneous source field is investigated in terms of high and finite-frequency regimes. Graphical software for phase-velocity dispersion measurements based on new algorithms is presented and validated with synthetic data and by comparisons to other methods. The software is used for phase-velocity measurements, and deduced azimuthal source distributions are used for velocity-bias correction. Derived phase-velocity dispersion curves are used to construct two-dimensional velocity maps of southern Sweden at different periods based on travel-time tomography. The effect of the bias correction is investigated, and velocity maps are interpreted in comparison to previous geological and geophysical information.
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Lynner, Colton y Robert W. Porritt. "Crustal structure across the eastern North American margin from ambient noise tomography". AMER GEOPHYSICAL UNION, 2017. http://hdl.handle.net/10150/625356.
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Passive tectonic margins, like the eastern North American margin (ENAM), represent the meeting of oceanic and continental material where no active deformation is occurring. The recent ENAM Community Seismic Experiment provides an opportunity to examine the crustal structure across the ENAM owing to the simultaneous deployment of offshore and onshore seismic instrumentation. Using Rayleigh wave phase and group velocities derived from ambient noise data, we invert for shear velocity across the ENAM. We observe a region of transitional crustal thicknesses that connects the oceanic and continental crusts. Associated with the transitional crust is a localized positive gravitational anomaly. Farther east, the East Coast magnetic anomaly (ECMA) is located at the intersection of the transitional and oceanic crusts. We propose that underplating of dense magmatic material along the bottom of the transitional crust is responsible for the gravitational anomaly and that the ECMA demarks the location of initial oceanic crustal formation.
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Ashruf, Tahira Nicole <1990>. "The Moho reflectivity from ambient seismic noise autocorrelations beneath the Western Alps". Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2022. http://amsdottorato.unibo.it/10491/1/Thesis30Sept_TahiraNicoleAshruf.pdf.
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The lower crustal structure beneath the Western Alps -- including the Moho -- bears the signature of past and present geodynamic processes. It has been the subject of many studies until now. However, its current knowledge still leaves significant open questions. In order to derive new information, independent from previous determinations, here I wish to address this topic using a different method --- ambient seismic noise autocorrelation --- that is for the first time applied to reveal Moho depth in the Western Alps. Moho reflections are identified by picking reflectivity changes in ambient seismic noise autocorrelations. The seismic data is retrieved from more than 200 broadband seismic stations, from the China--Italy--France Alps (CIFALPS) linear seismic network, and from a subset of the AlpArray Seismic Network (AASN). The automatically-picked reflectivity changes along the CIFALPS transect in the southwestern Alps show the best results in the 0.5--1 Hz frequency band. The autocorrelation reflectivity profile of the CIFALPS transect shows a steeper subduction profile,~55 to ~70 km, of the European Plate underneath the Adriatic Plate. The dense spacing of the CIFALPS network facilitates the detection of lateral continuity of crustal structure, and of the Ivrea mantle wedge reaching shallow crustal depths in the southwestern Alps. The data of the AASN stations are filtered in the 0.4--1 and 0.5--1 Hz frequency bands. Although the majority of the stations give the same Moho depth for the different frequency bands, the few stations with different Moho depths shows the care that has to be taken when choosing the frequency band for filtering the autocorrelation stacks. The new Moho depth maps by using the AASN stations are a compilation of the first and second picked reflectivity changes. The results show the complex crust-mantle structure with clear differences between the northwestern and southwestern Alps.
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Li, Zizheng. "Vertical Noise Structure and Target Detection Performance in Deep Ocean Environments". PDXScholar, 2010. https://pdxscholar.library.pdx.edu/open_access_etds/138.
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In passive sonar systems, knowledge of low-frequency shipping noise is an important factor for target detection performance. However, an accurate model for the shipping noise structure is difficult to obtain, due to the varying distributions of ships and complicated underwater environment. This work characterizes low-frequency distant shipping noise observed in deep water environments as a function of receiver depth and vertical arrival structure for the case of a receiver below the conjugate depth. Surface shipping noise is examined using Monte Carlo simulations using a normal mode propagation model based on random distribution of ships and realistic parameters. The depth dependence of the simulated distant shipping noise is in agreement with published experimental measurements. A Vertical Line Array (VLA) is used to produce vertical beams that isolate the surface interference from nearby targets. Simulation results quantifying the beamformer output as a function of ocean environment, receiver aperture, and frequency are presented for both conventional and adaptive beamformers. The results suggest that conventional beamforming could detect the noisy target from both direct arrival and bottom bounce in the presence of distant shipping interferers and wind noise. However, the beamwidth of conventional beamforming is wider than that of adaptive beamforming. Once the motion effects of nearby ship interferences are considered, the adaptive beamforming using diagonal loading provides better detection performance. Preliminary adaptive beamforming results corresponding to different snapshot times show that motion effects can be minimized by using short observation times.
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Saygin, Erdinc y erdinc saygin@anu edu au. "Seismic Receiver and Noise Correlation Based Studies in Australia". The Australian National University. Research School of Earth Sciences, 2007. http://thesis.anu.edu.au./public/adt-ANU20091009.115242.
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This thesis is directed at exploiting information in the coda of
seismic phases and the ambient noise field to provide new constraints
on the structure of the Australian Continent.
¶
The exploitation of the immediate coda following the onset of P waves from
a distant earthquake using radial receiver functions is now a well
established method. The 40 sec interval following P contains
reverberations and conversions, by deconvolving the radial component
trace with the vertical components, the conversions are emphasized
by canceling the part of the response that are common to both
components. A member of different styles of such deconvolution, are
investigated and a variant of the multitaper method is adopted for
subsequent applications. The TASMAL experiment 2003-2005
spans the expected location of the transition between Precambrian and
Phanerozoic Australia. The 20 portable broadband stations were
exploited in receiver function studies to extract S wave crustal
structure through the inversion of stacked receiver functions using the
Neighbourhood Algorithm. There is no clear crustal transition
associated with the presence of Tasman Line. The Precambrian Cratons
tend to exhibit crustal thicknesses close to 40 km but such values
are also found in some Phanerozoic sites.
¶
The second part of the thesis is directed at the exploitation of
ambient noise or seismic coda to gain information on the Green's
function between seismic stations. The TASMAL experiment
covered a significant fraction of the Australian continent with a
simultaneous deployment of portable broadband stations. From these
continuous records, it has proved possible to extract very clear
Rayleigh wave signals for station separations up to 2000 km, and to
demonstrate the frequency dependent variations in group velocity
behaviour. The combination of the paths between the 20 stations localize such
behaviour, but detailed images needed more data. The entire archive of
portable broadband data recorded by RSES was mined, and
combined with data from permanent stations to provide more than 1100
estimates of interstation Green's functions within Australia. Group
velocity analysis as function of frequency was followed by nonlinear
tomography with the Fast Marching Method. The resulting images of
group velocity patterns as a function frequency show pronounced regions
of lowered group velocities, most of which match regions of thick
sediment. The frequency dependence is not consistent with just
sedimentary structure and low midcrustal velocities, most likely due
to elevated temperatures, are also needed.
¶
The surface wave portion of the interstation Green's function is the
most energetic, and is normally all that seen in ambient noise
studies. However, in the coda of events record at the broadband
Warramunga seismic array in the Northern Territory, the P and S
body wave components also emerge. The characteristics of these
arrivals match those observed from
nearby small earthquakes. The stacked cross-correlation is the normal
approach to enhance Green's function information from ambient noise,
but a broader spectral band width with the same phase response can be
found by spectral division. It appears advantageous to compare both
approaches and select the best result, since very little modifications
to procedures are needed.
¶
The properties of the ambient noise at a single station have been
investigated in the logarithmic spectral domain and a station
dependent signal can be extracted by stacking. The signal appears to
be related to the local structure beneath the station, and when fully
characterized may provide a new means of investigating structure.
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Collins, David A. "Development of a low frequency ambient noise storm model for the Arctic Ocean". Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 1996. http://handle.dtic.mil/100.2/ADA325452.
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Thesis (M.S. in Physical Oceanography) Naval Postgraduate School, December 1996.Thesis advisor(s): Robert H. Bourke, James H. Wilson. "December 1996." Includes bibliographical references (p. 131-132). Also available online.
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Hipsey, Stephen J. "Ambient noise due to the shearing of the boundary layer under sea ice". Thesis, Monterey, California. Naval Postgraduate School, 1988. http://hdl.handle.net/10945/22869.
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Huang, Hui Ph D. Massachusetts Institute of Technology. "Ambient noise tomography for wavespeed and anisotropy in the crust of southwestern China". Thesis, Massachusetts Institute of Technology, 2014. http://hdl.handle.net/1721.1/87518.
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Thesis: Ph. D., Massachusetts Institute of Technology, Department of Earth, Atmospheric, and Planetary Sciences, 2014.Cataloged from PDF version of thesis.
Includes bibliographical references.
The primary objective of this thesis is to improve our understanding of the crustal structure and deformation in the southeastern Tibetan Plateau and adjacent regions using surface wave tomography. Green's functions for Rayleigh and Love waves are extracted from ambient noise interferometry. Using the Green's functions, we first conduct traditional traveltime tomography for the two shear wavespeeds Vsv and Vsh Their differences are measured as radial anisotropy. We then conduct Eikonal tomography to study azimuthal anisotropy in the crust. Our tomography results are well consistent with geology in the study region. In the Sichuan Basin, low wavespeed and positive radial anisotropy (Vsh> Vsv) in the upper crust reflect thick sedimentary layers at surface; high wavespeed and small radial anisotropy in the middle and lower crust reflect a cold and rigid basin root. Little azimuthal anisotropy is observed in the Basin, indicating small internal deformation. In the Tibetan Plateau, we observe widespread low wavespeed zones with positive anisotropy in the middle and lower crust, which may reflect combined effects of weakened rock mechanism and horizontal flow in the deep crust of southeastern Tibet. The northern part of the Central Yunnan block, which geographically coincides with the inner zone of the Emeishan flood basalt, reveals relatively higher wavespeeds than the surrounding regions and little radial anisotropy throughout the entire crust. We speculate that the high wavespeeds and small radial anisotropy are due to combined effects of the remnants of intruded material from mantle with sub-vertical structures and channel flow with sub-horizontal structures. In general, the azimuthal anisotropy in our study region is consistent with a clockwise rotation around the Eastern Himalayan Syntaxis. Careful examination reveals large angular differences between the azimuthal anisotropy in the upper and lower crust, suggesting different deformation patterns at the surface and in depth. Therefore, our tomography results support models with ductile flow in the deep crust of the southeastern Tibetan Plateau; however, the large lateral variation of both wavespeeds and anisotropy indicates that the flow also varies greatly in intensity and pattern in different geological units.
by Hui Huang.
Ph. D.
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Arriaza, Barriga Romina Carolina. "Implementation of synthetic scenarios for the study of the ambient noise tomography technique". Tesis, Universidad de Chile, 2017. http://repositorio.uchile.cl/handle/2250/149595.
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Magíster en Ciencias de la Ingeniería, Mención Eléctrica.
Ingeniera Civil EléctricaLa Tomografía de Ruido Ambiente (ANT) consiste en una técnica de busca modelar áreas y estructuras cuya novedad es que utiliza el ruido ambiente como herramienta. Este tipo de señal suele ser eliminada en técnicas como la Tomografía Sísmica (TS), la cual es la más ampliamente utilizada, especialmente en el área de la minería para la exploración de yacimientos. A diferencia de ANT, ésta hace uso señales de alta energía como terremotos y explosiones artificiales, por lo tanto, dentro de su procesamiento elimina este ruido. En zonas con baja actividad sísmica no es posible utilizar TS, por lo que es necesario desarrollar técnicas alternativas. ANT es una de las opciones que cumple, además de ser amigable con el medio ambiente. Una de las problemáticas tanto de ANT es que no cuenta con un ground-truth. Dado esto, no se puede saber con certeza qué tan cercano es el modelo estimado a la realidad. Para intentar resolver esto, actualmente sismólogos contrastran los resultados provenientes de ST o usan información de previo conocimiento del área, pero no es suficiente. Era necesario el desarrollo de una plataforma sintética, que fuera lo más cercano a la realidad posible. Sobre ésta se implementa la técnica de tomografía de ruido, con el objetivo de identificar las variables que influyen en la estimación, tales como la posición de estaciones, la frecuencia de la fuente, velocidad del medio, entre otras. También esta plataforma debe cuenta con un ground-truth para determinar los errores de estimación. En el presente trabajo, ésta plataforma fue implementada en lenguaje Python. Cada etapa de la metodología y fue probada sobre tres escenarios sintéticos con diferentes caracteríasticas de estructura. Se estudiaron las variables de interés y se realizó un análisis sobre cada etapa. También se logró entregar una visualización clara y apropiada de los resultados. Este trabajo sirvió para crear una base de conocimiento sobre esta nueva técnica para que pueda continuar siendo desarrollada y mejorada. Diversas mejoras potenciales fueron identificadas y se entregaron diversas soluciones para su posterior implementación en futuras campañas para el mejor provecho de los recursos existentes.
Este trabajo ha sido parcialmente financiado por Proyecto CORFO 14IDL4-300327 EXPLORACIÓN MINERA POR TOMOGRAFÍA SÍSMICA
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Fégeant, Olivier. "Noise from wind turbines". Doctoral thesis, KTH, Byggnader och installationer, 2001. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-3100.
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A rapid growth of installed wind power capacity is expectedin the next few years. However, the siting of wind turbines ona large scale raises concerns about their environmental impact,notably with respect to noise. To this end, variable speed windturbines offer a promising solution for applications in denselypopulated areas like the European countries, as this designwould enable an efficient utilisation of the masking effect dueto ambient noise. In rural and recreational areas where windturbines are sited, the ambient noise originates from theaction of wind on the vegetation and about the listener's ear(pseudo-noise). It shows a wind speed dependence similar tothat of the noise from a variable speed wind turbine and cantherefore mask the latter for a wide range of conditions.However, a problem inherent to the design of these machines istheir proclivity to pure tone generation, because of theenhanced difficulty of avoiding structural resonances in themechanical parts. Pure tones are deemed highly annoying and areseverely regulated by most noise policies. In relation to thisproblem, the vibration transmission of structure-borne sound tothe tower of the turbine is investigated, in particular whenthe tower is stiffened at its upper end. Furthermore, sincenoise annoyance due to wind turbine is mostly a masking issue,the wind-related sources of ambient noise are studied and theirmasking potentials assessed. With this aim, prediction modelsfor wind-induced vegetation noise and pseudo-noise have beendeveloped. Finally, closely related to the effect of masking,is the difficulty, regularly encountered by local authoritiesand wind farm developers, to measure noise immission from windturbines. A new measurement technique has thus been developedin the course of this work. Through improving thesignal-to-noise ratio between wind turbine noise and ambientnoise, the new technique yields more accurate measurementresults. Keywords: Masking, vibration transmission, diffraction,ambient noise, pseudo-noise, cylindrical shell, perturbationmethods, structural mobility, acoustic outdoor measurement.QC 20100616
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Liu, Jin-Yuan. "Seismo-acoustic rough interface scattering of surface-generated ambient noise in a stratified ocean". Thesis, Massachusetts Institute of Technology, 1992. http://hdl.handle.net/1721.1/44398.
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Richmond, Rachelle Marie. "Ambient noise surface wave tomography across Europe: Rayleigh wave group and phase speed measurements". Connect to online resource, 2008. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:1453514.
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Soars, Natalie Anne. "Habitat soundscapes and sound production by tropical and temperate sea urchins and the swimming behaviour of their larvae". Thesis, The University of Sydney, 2014. http://hdl.handle.net/2123/13923.
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The distribution, abundance and behaviour of soniferous organisms influence the spatial variability of underwater noise characteristics or ‘soundscape’. In this way, the soundscape provides useful information on habitat and assemblages that enables navigation in larvae and can be used for environmental assessment and monitoring. Despite the ecological importance of sea urchins and evidence they produce sound of their sound, knowledge gaps remain regarding the role of adult and larval sea urchins in acoustic ecology. In this thesis the sounds produced by 3 temperate and 3 tropical species of sea urchins were characterised. The soundscape of sea urchin habitat from important ecological systems (sea grass, temperate rocky reef, coral reef) in eastern Australia were also characterised. The sea urchins made a ‘crunching’ sound when feeding that was commonly produced around dawn, dusk or midnight. This sound ranged from 2-22 kHz with highest intensity from 2-8 kHz. Centrostephanus rodgersii appeared to contribute to a diurnal chorus between 2-8 kHz in the ‘barrens’ habitat of Jervis Bay, NSW. Analysis of the 5000 Hz 1/3rd octave band revealed a difference between barrens sites of up to 10 dB re 1 µPa2. A similar difference was found between two coral reef habitats recorded at One Tree Island, QLD. Arm angle development reflects swimming ability in sea urchin larvae and so was documented for two-armed and multi-armed larvae forms to characterise their swimming biology. In a behavioural study of early and settlement stage larvae of H. tuberculata and C. rodgersii, early stage larvae exhibited signs of negative phototaxis swimming down during the day, suggesting that they exhibit diurnal migration in the field. However, larvae did not modify this swimming behaviour in response to a reef noise. This research will enable detection of sea urchin sounds in ambient noise recordings and provides insight into the impacts of sea urchin populations on the marine soundscape.
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O'Connor, Jody Lynn. "A Comparison of Ambient and Hearing Aid Output Noise Levels in Industrial and Non-industrial Settings". PDXScholar, 1993. https://pdxscholar.library.pdx.edu/open_access_etds/5147.
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Federal regulations specify that an employee working for eight hours cannot legally be exposed to noise which has a time-weighted average greater than 90 decibels on the A scale. The industrial workforce is comprised of not only people with normal hearing acuity, but of individuals who suffer from hearing loss. While current noise regulation standards are deemed appropriate for those with normal hearing, it is difficult to apply these standards to persons wearing hearing aids on the job. The ambient, or unamplified, noise levels that fall below the maximum permitted by OSHA standards may very well be amplified to levels greater than 90 dBA, by the hearing aid. If this were the case, the company employing the hearing aid user would technically be in violation of the OSHA regulations. This study addressed the question of what noise exposure might be expected for hearing aid users on the job in different situations, as well as in non-vocational settings. The research involved two methods, conducted to determine the noise levels created by hearing aids with different amounts of gain and to determine whether the amplified noise levels exceed those requiring intervention under current regulations. For both methods, ambient and amplified noise levels for each condition were gathered in specified increments, and were compared with regard to current regulatory standards. The resultant data revealed that when ambient noise levels average between 80 and 84 dBA, amplification provided by even a mild gain hearing aid caused the eight hour time-weighted averages (TWA's) to increase to levels above the 90 dBA maximum permissible levels as delineated by OSHA. Moderate and high gain aids further increased these levels. The results of this study suggest that the hearing aid users in industrial and perhaps non-industrial settings may very well be exposed to intensity levels which exceed OSHA maximums, even when ambient levels do not. The extent to which these arc exceeded are based on the gain and output of the hearing aid in use.
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Sabey, Lindsay Erin. "Body and surface wave ambient noise seismic interferometry across the Salton Sea Geothermal Field, California". Thesis, Virginia Tech, 2015. http://hdl.handle.net/10919/51185.
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Virtual source gathers were generated using the principles of seismic interferometry from 135 hours of ambient noise recorded during a controlled-source survey across the Salton Sea Geothermal Field in southern California. The non-uniform nature of the noise sources violated a primary assumption of the method and generated artifacts in the data. The artifacts generated by the high-energy impulsive sources (e.g. earthquakes, shots) were removable using traditional methods of amplitude normalization prior to cross-correlation. The continuous source artifacts generated by the geothermal wells and highways required an unconventional approach of utilizing only normalized impulsive sources to successfully reduce the artifacts. Virtual source gathers were produced successfully that contained strong surface waves at 0.4-2.5 Hz, an order of magnitude below the corner frequency of the geophones, and modest body waves at 22-30 Hz, which are generally more difficult to obtain due to the need for many large, well-distributed subsurface sources. The virtual source gathers compare well to nearby explosive shots and are more densely spaced, but have a much lower signal-to-noise ratio. Analysis of the surface waves was complicated by strong higher-order modes. Spectral analysis of virtual source gathers required utilization of the geothermal plant energy, which produced usable signal at offsets required for mode separation. The virtual source dispersion curve compared well to a dispersion curve from a nearby explosive shot. P-waves were observed on the virtual source gathers. Creation of a low-quality multichannel reflection stack revealed two weak reflectors in the upper 2 km.Master of Science
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Bensen, Gregory David. "Broad-band ambient noise surface wave tomography: Technique development and application across the United States". Connect to online resource, 2007. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:3284458.
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Liu, Chuang. "Exposure to ambient air pollution and noise in relation to adverse health effect in children". Diss., Ludwig-Maximilians-Universität München, 2014. http://nbn-resolving.de/urn:nbn:de:bvb:19-173416.
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Adverse health impacts of ambient air pollution and noise have been reported previously. However, many published studies were in adults or aged population, little attention has been paid to children and in particular to noise and the potential combined effect with air pollution. In addition, we considered health parameters, which are underinvestigated so far. In our study, we explored associations between ambient air pollution and noise with blood pressure (BP), and exhaled nitric oxide (eNO) in school-aged children, using data from two German birth cohorts.
Noise levels within a 50m buffer around each participant’s home address were assessed using geographic information system. Exposure estimates of annual average concentrations of air pollution for each participant’s residence were calculated using a land use regression model. Short-term concentrations of air pollution were collected from background monitoring sites. Information on BP and eNO was collected during a physical examination at the 10-year follow-up of the cohorts.
We studied the health impacts of ambient air pollution and noise in children from three different aspects. The association between traffic noise and BP was explored in 605 children, and the results showed that higher minimum levels of weighted day-evening-night noise and nighttime noise around the home residence may increase a child’s BP. Based on this finding, we conducted a second analysis to figure out the combined associations between air pollution and noise with BP, and found that ambient air pollution was not consistently associated with BP with adjustment for noise. Furthermore, the effects of ambient air pollution on eNO were explored within 1985 children, and we observed a significant positive association between short-term, but not long-term, air pollution with childhood eNO.
In conclusion, our study provided more epidemiological evidence on the adverse health impacts of ambient air pollution and noise in school-aged children, and highlighted the confounding association between ambient air pollution and noise. More studies are needed to better assess the combined health effects of ambient air pollution and noise in children.Frühere Studien haben über die gesundheitsschädigende Wirkung von Luftschadstoffen und Lärm berichtet. Allerdings betrachteten viele bislang publizierte Studien Erwachsene oder die ältere Bevölkerung. Kinder und im Speziellen die gesundheitlichen Auswirkungen von Lärm, sowie die gemeinsame Wirkung von Luftschadstoffen und Lärm wurden hingegen bislang nur wenig untersucht. Das ist ein Ziel der vorliegenden Promotionsschrift. Zusätzlich haben wir Gesundheitsgrößen betrachtet, die bisher wenig erforscht wurden. In unserer Studie haben wir die Assoziationen zwischen Luftschadstoffen und Lärmbelastung und Blutdruck und exhaliertem Stickstoffmonoxid (eNO) bei Kindern im Schulalter untersucht. Wir konnten dabei auf Daten von zwei großen deutschen Geburtskohorten zurückgreifen. Die Lärmbelastung innerhalb eines Umkreises von 50m um die Wohnadresse jedes Studienteilnehmers wurde anhand von Lärmpegelkarten im Geographischen Informationssystem modelliert. Schätzungen der mittleren jährlichen Konzentration von Luftschadstoffen an der jeweiligen Wohnadresse wurden anhand von „land use regression“ Modellen berechnet. Kurzzeit-Konzentrationen von Luftschadstoffen wurden mit Hilfe von Hintergrund Monitoring Stationen gesammelt. Informationen zu Blutdruck und eNO wurden während einer körperlichen Untersuchung beim Follow-up der Kohorten im Alter von 10 Jahren gemessen. Wir haben die Auswirkungen von Luftschadstoffexposition und Lärmbelastung auf die Gesundheit von Kindern unter drei verschiedenen Aspekten betrachtet. Der Zusammenhang zwischen Verkehrslärm und Blutdruck wurde bei 605 Kindern untersucht und die Ergebnisse legen nahe, dass ein höherer Mindestpegel des gewichteten Tag-Abend-Nacht Lärmes und des Lärmes während der Nachtzeit um die Wohnung den Blutdruck der Kinder erhöhen könnte. Auf Grund dieser Erkenntnis haben wir eine zweite Auswertung durchgeführt um den gemeinsamen Zusammenhang zwischen Luftschadstoffbelastung und Lärm mit Blutdruck zu untersuchen und haben festgestellt, dass die Luftschadstoffexposition nach einer Adjustierung für Lärm nicht konsistent mit Blutdruck assoziiert war. Darüber hinaus wurden die Auswirkungen der Luftverschmutzung auf das eNO bei 1985 Kindern untersucht. Dabei wurde ein signifikanter, positiver Zusammenhang zwischen Kurzzeit-, jedoch nicht zwischen Langzeitexposition mit Luftschadstoffen und eNO beobachtet. Zusammenfassend lässt sich festhalten, dass unsere Studie weitere epidemiologische Erkenntnisse über die negativen gesundheitlichen Auswirkungen von Luftverschmutzung und Lärm bei Schulkindern geliefert hat. Insbesondere wird damit betont, dass Luftschadstoffe und Lärm wechselseitige Störgrößen in Assoziationen darstellen können. Allerdings sind weitere Studien notwendig, um gesundheitliche Auswirkungen von Luftschadstoffen auf die Knochenumsatzrate bei Kindern abschließend beurteilen zu können.
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Feller, David. "Environmental forcing of ambient noise in the Nansen and Amundsen Basins of the Arctic Ocean". Thesis, Monterey, California. Naval Postgraduate School, 1994. http://hdl.handle.net/10945/42980.
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Approved for public release, distribution unlimitedThis Thesis addresses the question of Syria's pro-western tilt in foreign policy over the last few years. The most common argument, that the shift occurred because of the demise of the USSR (Syria's primary patron) is inaccurate. Rather, this thesis proves that changes in Syria's foreign policy began in the mid-198Os ,not in 1991, and were driven primarily by domestic economic factors, not by international structures. Syria's increasingly pro-Western foreign policy was a byproduct of economic liberalization policies begun in the early 198Os. For economic liberalization to succeed, Syria had to attract foreign,primarily Western capital. In addition, the liberalization changed Syria's class structure, expanding and promoting to positions of influence a new class of Western educated entrepreneurs. Both of these developments pushed Syria in new foreign policy directions well before the collapse of the USSR. Its behavior in the Gulf War and at the Madrid Conference was more a reflection of altered Syrian internal politics than of the recognition that the United States was the only true superpower in a changed international system. This thesis has important policy and theoretical applications. It identifies the driving forces of Syria's current foreign policy behavior, and it pushes theorists to take seriously the domestic roots of foreign policy making.
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Shao-Chi, Lin y 林紹麒. "Effects of ambient noise on mobile audiometric room background noise measurement". Thesis, 2015. http://ndltd.ncl.edu.tw/handle/53027974098336029012.
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碩士中華醫事科技大學
職業安全衛生系暨碩士班
103
The audiometric room is major equipment for pure tone audiometry. The quiet environment quality in audiometric room is required for the accurate hearing level measurement. The purpose of this study is to investigate the effects of background noise on audiometric test room in the field using semi-experiment design. The ambient noise level between 60 and 85 dBA was simulated by audio auto-play system when the test was performed on four different mobile audiometric testing facilities. The noise spectra were recorded at three locations (inside testing room, in the facility and outside of the facility) for one minute at least three times when the ventilation system was turned on or turned off respectively. The collected data were then evaluated by three standards (ANSI S3.1-1999, OSHA-1983 and ISO 8253-1-2010). The results showed that most of the test for low frequency (≦500 Hz) were not meet these criteria under the ventilation system was turned on. The unqualified percentage of the audiometric room increased with the increasing ambient noise level. As the testing room location approaching to motor of ventilation system, the remarkable unqualified percentage also observed. According to the finding, it was concluded that the background noise of audiometric testing room can not fulfilled ANSI-1999 and ISO-2010 standard when the ventilation system was turn-off and ambient noise level greater than 80 dBA. Therefore, to control the quality of audiometric testing, the ambient background noise less than 75 dBA for hearing test by pure-tone audiometry is strongly suggested.
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Lai, Han-Wen y 賴漢文. "Influence of Ambient Noise on Study Performance". Thesis, 2008. http://ndltd.ncl.edu.tw/handle/62105845364242446905.
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碩士立德大學
資源環境研究所
96
This study aims to investigate the effect of noise on students’ learning effects. Tsung Shang Elementary School in Dacun country of Changhua County was taken as example for studying, which includes thirty-two teachers, two hundred and twelve students. The studying methods included on field noise measuring, questionnaire investigation, students’ addition test, and the performance test of students on social subject studying. The research data were tested by the software of SPSS for window 12.0, including descriptive statistics, frequency theory, T-test, and ANOVA…etc. The result revealed that field ambient noise in the school always exceeded those standardized by Environmental Protection Administration, especially in the situation of teacher using a microphone in class or students being at the playground in physical education class. The value of Leq reached as high as 75.65 dB(A). Through questionnaires study, what affected the most on the students’ study performance by noise was in math subject study (22.6%), and followed by in social subject study (19.7%). Furthermore, a student concentrating on thinking subject (example as math subject) in quiet environment was more effective than one was in noisy environment; and the same result was found in memorizing subject (such as social subject). In other words, students had better study performance in the environment of high signal-to-noise ratio than in that of low signal-to-noise ratio. According to the result of this study, teachers should be more careful as using a microphone in class. Dividing teaching area from sporting area at school is required. May it hope that this study could provide a suggestion on planning school’s learning environment.
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Greening, Michael Victor. "A two-component Arctic ambient noise model". Thesis, 1994. http://hdl.handle.net/2429/6916.
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Short term Arctic ambient noise spectra over the frequency band 2 - 200
Hz are presented along with a two component noise model capable of reproducing
these spectra. The model is based on the measured source spectrum and the spatial,
temporal and source level distributions of both active pressure ridging and thermal
ice cracking. Modeled ambient noise levels are determined by summing the input
energy of the distributions of ice cracking and pressure ridging events and removing
the propagation loss.
Measurements were obtained on a 22-element vertical array along with a 7-element
horizontal array deployed beneath the Arctic pack ice in 420 meters of water. Over
900 thermal ice-cracking events were detected in approximately 2 hours of data col
lected over several days during April 1988. The source directivity for events beyond
40 wavelengths range was found to be accurately represented by a dipole with an
approximate 3 dB increase above the dipole directivity pattern near 60° - 65° caused
by the leaked longitudinal plate wave. A technique for measuring the bottom reflectivity function by correcting the bottom reflection of a thermal ice crack for the
measured directivity is presented. The spatial distribution of thermal ice-cracking
events is consistent with a uniform distribution. Source levels were measured from
110 to 180 dB //μPa²/ Hz at 1 m with the distribution of all events approximating a
linearly decreasing function on a log-dB scale of the number of events versus source
level.
Near the end of the data collection period, measurements from a nearby active
pressure ridge were obtained. Evidence is presented that the infrasonic peak observed
near 10 Hz in Arctic ambient noise spectra may result from a frequency dependent
propagation loss acting on the source spectrum of pressure ridging.
Both modeled and measured ambient noise spectra show that ice cracking may
dominate the spring-time ambient noise to frequencies as low 40 Hz. Below 40 Hz, the
ambient noise is dominated by a single or few active pressure ridges at ranges of tens
of kilometers. Above 40 Hz, the ambient noise is dominated by a large distribution of
thermal ice-cracking events with over 50% of the total noise level produced by events
within 6 km range and over 80% produced by events within 30 km range.