Academic literature on the topic 'Overall sound pressure levels'

A new method of reducing the noise of the linear guideway type recirculating linear ball bearing (linear bearing) was studied. In the experiments, the overall sound pressure levels of linear bearings with steel balls or ceramic Si3N4 balls were measured, and sound frequency analyses were carried out. Moreover, based on the assumption that the main cause of the noise may be the collision between the ball and the carriage, the overall sound pressure levels of the linear bearings were analyzed combining the Hertzian theory and the results of previous studies on collision sound. From the results of experiments and analyses, the conclusions were obtained as follows: (1) The overall sound pressure level of the linear bearing with steel balls can be reduced by about 4.5 dB by using Si3N4 balls having the same diameter; (2) The overall sound pressure levels of linear bearings with steel balls or ceramic Si3N4 balls were both increased by about 9.8 dB as the linear velocity increased an octave; and (3) The analytical results, based on the assumption that the main cause of the noise emitted from the linear bearings is the collision between the ball and the carriage, match the experimental results well.

Differences in real ear sound pressure levels (SPLs) with three portable stereo system (PSS) earphones (supraaural [Sony Model MDR-44], semiaural [Sony Model MDR-A15L], and insert [Sony Model MDR-E225]) were investigated. Twelve adult men served as subjects. Frequency response, high frequency average (HFA) output, peak output, peak output frequency, and overall RMS output for each PSS earphone were obtained with a probe tube microphone system (Fonix 6500 Hearing Aid Test System). Results indicated a significant difference in mean RMS outputs with nonsignificant differences in mean HFA outputs, peak outputs, and peak output frequencies among PSS earphones. Differences in mean overall RMS outputs were attributed to differences in low-frequency effects that were observed among the frequency responses of the three PSS earphones. It is suggested that one cannot assume equivalent real ear SPLs, with equivalent inputs, among different styles of PSS earphones.

Drum brakes are significant contributors to noise and vibration in automobiles causing discomfort to the passengers. The vibration and hence the resulting noise increase due to various inherent defects in the drum brake, such as asymmetry. This work aims to quantify the variation in the vibro-acoustic noise due to several common defects in the drum brake using an integrated non-linear vibration analytical model and a numerical acoustic model. The sources of vibro-acoustic noise sources such as contact and reaction forces are predicted using a four-degree-of-freedom non-linear contact mechanics based analytical model. A finite element based acoustic model of the drum brake is utilized to predict the force to the sound pressure transfer function in the drum brake. Product of the transfer functions and the forces gives the corresponding sound pressure level from which the overall sound pressure levels are estimated. The variation in the overall sound pressure levels due to different drum brake defects is evaluated by introducing defects to the analytical model. The results show that the overall sound pressure level is a strong function of the defects. It is envisioned that the current work will help in the development of effective health monitoring systems.

The hour-long duration acoustic fatigue tests at levels above 190 dB overall sound pressure level (OASPL) can be achieved with the required sound pressure level (SPL) spectrum using available test facilities with a hydraulic simulator, which operates at only 3 to 10 psi. Furthermore, the hydraulic control at the low frequencies is available, whereas there is a 50-Hz frequency cutoff for acoustic test facilities. Many structures have destructive low-frequency resonant modes which would be properly excited in the hydraulic facility and not in the acoustic facility.

The flow field and sound propagation around a three-coach 1/8th scale high-speed passenger train were obtained using a detached-eddy simulation and the Ffowcs-Williams and Hawkings acoustic analogy. The Reynolds number of flow based on the train height and speed was 2,000,000. The numerical results of the flow and aeroacoustic fields were validated using wind tunnel experiments and full-scale data, respectively. Features of overall sound pressure level, sound pressure level and A-weighted sound pressure level of typical measuring points are discussed. The sound propagated by a high-speed train is shown as a broadband noise spectrum including tonal component, where high sound pressure levels are concentrated on the low-frequency range from 10 Hz to 300 Hz. The inter-carriage gap is found to cause distinct tonal noise in contrast to the other parts of the train that cause a broadband noise. The negative log law has been used to study the influence of distance from the centre of track on the sound pressure level, where a good fit is shown at low-frequency ranges. The peak values of A-weighted sound pressure level from both full-scale experiment and simulation results occur at approximately 1 kHz, where simulation results show almost the same range as the experiment. The surface of each component of the train as well as the whole train are chosen as the integral surface for the Ffowcs-Williams and Hawkings computation of the far-field noise characteristics. It was found that the sound source generated by a high-speed train is mainly dipole, and the largest noise was obtained from the leading bogie. The results of this paper provide, for the first time, a better understanding of the aeroacoustic field around a three-coach train model, and the paper has the potential to assist engineers to design high-speed trains with aeroacoustic noise reduction in a better manner.

Tire-pavement interaction noise (TPIN, aka tire-road noise or tyre-road noise) is most efficiently measured in acoustically controlled laboratories with large diameter roadwheels (drums) that have surface treatments which replicate some pavement properties, especially when comparing the acoustic performance of different tires. However, it is not clear how closely the roadwheel replicates the road surface, including differences that include road curvature and mechanical impedance of pavements. On the other hand, measuring on a moving vehicle with a microphone array presents it own set of challenges. In this study, a Nearfield Acoustical Holography (NAH) method is used to measure tire/pavement interaction noise on roadways and roadwheels with similar smooth pavement and rough pavement properties. Sound intensity fields, overall sound power levels, and sound pressure levels are reconstructed very close to the tire surface. An experimental passenger car tire with a mono-pitch tread is used in this study. The experimental tire has three circumferential grooves and 64 equally spaced transverse grooves cut into the tread. Differences in sound fields and levels between roadway and roadwheel test conditions for this tire are shown.

This study examined the effect of aging on respiratory and laryngeal mechanisms involved in vocal loudness control. Simultaneous measures of subglottal pressure and electromyographic (EMG) activity from the thyroarytenoid (TA), lateral cricoarytenoid (LCA), and cricothyroid (CT) muscles were investigated in young and old individuals while they attempted to phonate at three loudness levels, "soft," "comfortable," and "loud." Voice sound pressure level (SPL) and fundamental frequency (F 0 ) measures were also obtained. Across loudness conditions, subglottal pressure levels were similar for both age groups. Laryngeal EMG measures tended to be lower and more variable for old compared with young individuals. These differences were most apparent for the TA muscle. Finally, across the three loudness conditions, the old individuals generated SPLs that were lower overall than those produced by the young individuals but modulated loudness levels in a manner similar to that of the young subjects. These findings suggest that the laryngeal mechanism may be more affected than the respiratory system in these old individuals and that these changes may affect vocal loudness levels.

Brown, M. C., S. G. Kujawa, and M. L. Duca. Single olivocochlear neurons in the guinea pig. I. Binaural facilitation of responses to high-level noise. J. Neurophysiol. 79: 3077–3087, 1998. Single medial olivocochlear (MOC) neurons were recorded from the cochlea of the anesthetized guinea pig. We used tones and noise presented monaurally and binaurally and measured responses for sounds up to 105 dB sound pressure level (SPL). For monaural sound, MOC neuron firing rates were usually higher for noise bursts than tone bursts, a situation not observed for afferent fibers of the auditory nerve that were sampled in the same preparations. MOC neurons also differed from afferent fibers in having less saturation of response. Some MOC neurons had responses that continued to increase even at high sound levels. Differences between MOC and afferent responses suggest that there is convergence in the pathway to olivocochlear neurons, possibly a combination of inputs that are at the characteristic frequency (CF) with others that are off the CF. Opposite-ear noise almost always facilitated the responses of MOC neurons to sounds in the main ear, the ear that best drives the unit. This binaural facilitation depends on several characteristics that pertain to the main ear: it is higher in neurons having a contralateral main ear (contra units), it is higher at main-ear sound levels that are moderate (∼65 dB SPL), and it is higher in neurons with low discharge rates to main-ear stimuli. Facilitation also depends on parameters of the opposite-ear sound: facilitation increases with noise level in the opposite ear until saturating, is greater for continuous noise than noise bursts, and is usually greater for noise than for tones. Using optimal opposite-ear facilitators and high-level stimuli, the firing rates of olivocochlear neurons range up to 140 spikes/s, whereas for moderate-level monaural stimuli the rates are <80 spikes/s. At high sound levels, firing rates of olivocochlear neurons increase with CF, an increase that may compensate for the known lower effectiveness of olivocochlear synapses on outer hair cells responding to high frequencies. Overall, our results demonstrate a high MOC response for binaural noise and suggest a prominent role for the MOC system in environments containing binaural noise of high level.

Lightweight floors are in line with a sustainable construction concept and have become increasingly popular in residential buildings. The acoustic performance of such floors plays a pivotal role in the overall building quality rating. There is, however, no clear and complete method to predict their impact sound insulation. A new approximation method and new acoustic indicators—equivalent weighted normalized impact sound pressure levels for lightweight floors—are proposed and outlined in this article. The prediction procedure and indicator values were initially validated on the basis of laboratory measurements taken for different lightweight floors with the same well-defined floor covering. These preliminary analyses and comparisons show that the proposed method is promising and should be fully developed on the basis of further research.

Research into the effects of soundscapes on aquaculture species in key production systems is sparse, despite potential impacts of sound on animal welfare and commercial yields. In the following study, 2 high-value global aquaculture species, whiteleg shrimp Litopenaeus vannamei and Atlantic salmon Salmo salar, were exposed to aquaculture production system soundscapes. For shrimp, sound recordings of a commercial recirculating aquaculture system (RAS) were played back at a sound pressure level (SPL) of 128 dB re 1 µPa, and for salmon, recordings from a commercial sea pen production system were played back at an SPL of 127 dB re 1 µPa for an 8 wk period. Effects of exposure on growth, survival, and indications of metabolic stress were measured as parameters of interest for aquaculture production. Mean growth performance and survival rates did not differ significantly between sound and control treatments for either species. Blood and haemolymph parameters from both species indicated no measurable change in metabolic status or stress levels. Slight, but non-significant, increases in total haemocyte count and, in particular, hyaline cell count were recorded in shrimp exposed to sound. Slight, but non-significant reductions in overall weight gain were recorded in sound-exposed salmon. Overall, the results indicate that sound exposure in current production systems does not negatively affect the early grow-out stage of these key species, either due to rapid habituation or higher hearing thresholds of hatchery-produced individuals, and that no measurable stress response occurs in sound-exposed animals. In future studies, response of the studied species to acute sound exposure and the response of earlier, and potentially more sensitive, life-stages will need to be determined to ensure optimal welfare and production performance.

The acoustic emissions from supersonic jets represent an area of significant research needs; not only in the field of aero-acoustics, but in industry as well where high pressure let down processes have been known to cause acoustically induced vibrations. A common method to reduce the acoustic emissions of such processes involves dividing the single larger supersonic flow into several smaller ones. Though this is common practice, there is not yet a current model which describes the reduction of acoustic emissions from an array of smaller supersonic jets. Current research which studies supersonic jet arrays are mainly focused on the effects of screech. Though screech is important, due to its high amplitude acoustic pressure, this research focuses on the overall acoustic emissions radiated from supersonic jet arrays which can cause severe acoustic loadings. This research investigated the acoustic emissions and shock formations from several eight by eight arrays of axisymmetric jet experimentally. The array nozzle diameters investigated ranged from 1/8 inch to 1/4 inch and the spacing over diameter ratio ranged from 1.44 to 3. The net pressure ratios investigated ranged from 2 to 24. Results revealed a strong correlation between the acoustic emissions and the shock formations of the flow. Up until a critical net pressure ratio, the overall sound pressure levels were comparable to that of a single jet within an array. At net pressure ratios beyond the critical the overall sound pressure levels transitioned to higher decibel levels; equivalent to a single jet with an equivalent exit area of an entire array. Also, the characteristic acoustic frequency emitted from a nozzle array remained ultrasonic (above 20 kHz) at lower net pressure ratios and then shifted to audible levels (between 20 Hz to 20 kHz) at net pressure ratios beyond the critical. Also, before the critical net pressure ratio the shock cells from the jets within the array remained unmerged, but at net pressure ratios beyond the critical the shock cells merged and formed lattices of weak oblique shocks at first and then strong oblique shocks as the net pressure ratio continued to increase. The critical net pressure ratio was investigated by non-dimensional analysis. The non-dimensional analysis revealed that the critical net pressure ratio was a strong linear function of the spacing over diameter ratio. A linear model was derived which is able to predict the critical net pressure ratio, and in turn, predict a critical shift in the acoustic emissions of a nozzle array.

The developments of new types of conductors and increase of voltage level have driven the need to carry out research on evaluating overhead line acoustic noise. The surface potential gradient of a conductor is a critical design parameter for planning overhead lines, as it determines the level of corona loss (CL), radio interference (RI), and audible noise (AN). The majority of existing models for surface gradient calculation are based on analytical methods which restrict their application in simulating complex surface geometries. This thesis proposes a novel method which utilizes both analytical and numerical procedures to predict the surface gradient. Stranding shape, proximity of tower, protrusions and bundle arrangements are considered within this model. One of UK National Grid's transmission line configurations has been selected as an example to compare the results for different methods. The different stranding shapes are a key variable in determining dry surface fields. The dynamic behaviour of water droplets subject to AC electric fields is investigated by experiment and finite element modelling. The motion of a water droplet is considered on the surface of a metallic sphere. To understand the consequences of vibration, the FEA model is introduced to study the dynamics of a single droplet in terms of phase shift between vibration and exciting voltage. Moreover, the evolution of electric field within the whole cycle of vibration is investigated. The profile of the electric field and the characteristics of mechanical vibration are evaluated. Surprisingly the phase shift between these characteristics results in the maximum field occurring when the droplet is in a flattened profile rather than when it is ‘pointed’.Research work on audible noise emitted from overhead line conductors is reviewed, and a unique experimental set up employing a semi-anechoic chamber and corona cage is described. Acoustically, this facility isolates undesirable background noise and provides a free-field test space inside the anechoic chamber. Electrically, the corona cage simulates a 3 m section of 400 kV overhead line conductors by achieving the equivalent surface gradient. UV imaging, acoustic measurements and a partial discharge detection system are employed as instrumentation. The acoustic and electrical performance is demonstrated through a series of experiments. Results are discussed, and the mechanisms for acoustic noise are considered. A strategy for evaluating the noise emission level for overhead line conductors is developed. Comments are made on predicting acoustic noise from overhead lines. The technical achievements of this thesis are summarized in three aspects. First of all, an FEA model is developed to calculate the surface electric field for overhead line conductors and this has been demonstrated as an efficient tool for power utilities in computing surface electric field especially for dry condition. The second achievement is the droplet vibration study which describes the droplets' behaviour under rain conditions, such as the phase shift between the voltage and the vibration magnitude, the ejection phenomena and the electric field enhancement due to the shape change of droplets. The third contribution is the development of a standardized procedure in assessing noise emission level and the characteristics of noise emissions for various types of existing conductors in National Grid.

Behovet av en mer mobil granatkastare har resulterat i en utredning av möjliga koncept som sedan ska gallras bort och resultera i en investering i ett nytt fordonsmonterat granatkastarsystem. Denna rapport beskriver utredningen av en potentiell risk med ett av de potentiella koncepten. Konceptet består av att placera en granatkastare i personalutrymmet i en stridsfordon90-vagn och avfyra den med öppna takluckor. Detta koncept har använts av andra länder och deras arméer, bland dem finns USA som använder sig av fordonsplattformen Stryker. Säkerheten för soldaterna i Försvarsmakten är högt prioriterat och strängt reglerat av standarder och reglementen som ständigt revideras. Den största potentiella risken med det aktuella konceptet har identifierats att vara ljudtrycksnivån som soldaterna utsätts för vid avfyrning. Om en undersökning av ljudtrycksnivåerna skulle visa att konceptet inte är säkert så finns därmed inget behov att vidare utreda konceptet och det skulle därmed bli uteslutet. För att fastställa vilka nivåer som kan förväntas av denna lösning så planerades och genomfördes en testskjutning med hjälp av FMV Test och Evaluering i Karlsborg samt representanter från BAE Systems Hägglunds. Provskjutningen genomfördes genom att placera den svenska 120mm granatkastaren M/41 i ett testchassi, som i stora drag motsvarar Strf90 chassiet, och sedan skjuta granater i flera olika testscenarion för att undersöka parametrarna elevation, laddning, riktning, användning av tratt, vinkel på takluckor öppen/stängd bakre lucka samt upphöjt chassi.Provet visade att dubbla hörselskydd kommer att behövas inne i fordonet och att potentiellt kommer personal längst in i fordonet att klara sig med enkla hörselskydd. Högst troligt är att det slutgiltiga konceptet kommer att ha en begränsning på 30-50 avfyrningar per dag med högsta laddning, 40-50 med laddning 7 och 70-80 med laddning 5. Användning av en tratt visade sig effektivt och minskade ljudtrycksnivån med 5-10 dB och därmed ökar antalet tillåtna avfyrningar till över 100 skott per dag för högsta laddningen.
The need of a more mobile mortar has led to an investigation of possible concepts which will be narrowed down and end in a purchase of a self-propelled mortar system. This report describes the exploration of a possible risk with one of these concepts. The concept is to place a mortar in the back storage area of a CV90 where it will be fired with open hatches. This concept has been used by other countries armies, amongst them the US Army which uses the Stryker vehicle platform.The safety of the personnel in the Swedish Army is prioritized and strictly regulated by set standards and regulations which are frequently revised. The largest potential risk with the concept in question has been identified to be the sound pressure acting on the personnel. If the concept would indicate levels over the permissible levels it would not have any potential and would not be further investigated.To conclude which levels a concept like this would have, a test shooting was planned and conducted with the help from FMV Test and Evaluation centre in Karlsborg and representatives from BAE Systems HägglundsThe shooting was conducted by placing the Swedish 120 mm mortar GRK M/41 inside a CV90 chassis mock-up and firing grenades in several scenarios which would test the different parameters; elevation, charge, direction, BAD, angle of roof hatches, open/closed rear door and elevated chassis.The test showed that double ear protectors will be needed in the vehicle and with the potential that it will suffice with single ear protectors for personnel furthest in the vehicle. It is most likely that it will be restrictions on number of permissible rounds fired per day of 30-50 firings for charge 9, 40-50 with charge 7 and 70-80 with charge 5.The use of BAD resulted in the sound level decreasing between 5-12 dB which would increase the restrictions to a maximum of 100 rounds per day for maximum charge.

Sound pressure level (SPL) is known to cause stress in cattle but is often overlooked as a potential source of fear for cattle when designing handling equipment. Current literature does not offer guidelines for the design of equipment with regard to SPL. It is, however, recommended that handling equipment should be designed to minimize the SPL during handling. The purpose of this experiment was to measure stress levels in a group of cattle which were subjected to a series of varying sounds in order to determine a design threshold limit for handling equipment. Treatments included two frequencies, 1 kHz and 8 kHz, and three intensities, 40, 80, and 120dB. These treatments were assigned to the cattle using a completely randomized two by three factorial design replicated three times for a total of 18 animals being tested. A computer generated noise at each level was played back to the animals once a week for 6 weeks. Stress levels were measured using both physiological (heart rate and eye temperature) and physical (sudden movement) measures. Experiments yielded mixed results and did not prove that any of the sound pressure levels tested had any great effect on the stress level of the cattle.

Thesis (Ph.D.)--Kent State University, 2007.
Title from PDF t.p. (viewed Mar. 31, 2008). Advisor: Linda B. Walker. Keywords: music, hearing, band directors, teachers, audiology, spl, musicians. Includes survery instrument. Includes bibliographical references (p. 171-182).

The research focusses on computational analysis of vortex generation behind A-Pillar of simplified model derived from Jaguar XF that excludes air from the underside of vehicle. This vortex formation contributes in generating wall pressure fluctuations especially at speeds higher than 100km/hr. It is a collaborative work between Cranfield University and Jaguar Land Rover. Three dimensional pressure based incompressible flow using Large Eddy Simulation turbulence model is selected for computational analysis in FLUENT v14. This used high parallel computing systems available in Cranfield University. In the initial phase, three grid resolutions (coarse, medium and fine) were prepared in ICEM CFD with fine case consisting of 10 million cells. Qualitative analysis includes extraction of slices, 3-D and surface streamlines and pressure and velocity contours for capturing the unsteadiness due to the vortex formation over the front side glass surface. The iso-surface of Q captures the unsteadiness at the A-Pillar wake and side mirror wake over front side glass surface. It also reveals that the range of length scales captured were limited even at the finest grid resolution. Quantitative analysis compares the mean pressure (Cp) data with JLR results. Probes were located at 51 locations over the front side glass window that showed a good comparison; specifically for the fine grid; with maximum variation incurred at probes located in separation areas. For predicting the wall pressure fluctuations, a total of ten probes were located over the front side glass window surface. The surface pressure (static) data was recorded for 1 sec of flow-time and later imported in MATLAB for post-processing. The results obtained in 1/3rd octave band showed that the large scales were too energetic and small scales are not captured. However, comparing sound pressure levels with the Aero-acoustic Wind Tunnel (AWT); provided by JLR; it is concluded that either the grid is too coarse to resolve higher frequencies or the numerical modelling used is too dissipative to benefits the use of LES.

Desmonte de rochas com explosivos em áreas próximas a residenciais têm ocorrido com frequência em várias localidades em todo o Brasil. Atividades relacionadas a mineração e em especial as detonações causam muitos problemas visto que geram incômodo às comunidades vizinhas resultante de níveis elevados de pressão acústica (ruído) na atmosfera e reclamações de rachaduras em paredes das residências associadas com a propagação de vibrações no terreno. A necessidade de se obter uma melhor compreensão de como estruturas típicas da construção civil nacional respondem as vibrações geradas pelas detonações se torna evidente, bem como uma avaliação conjunta da influência de outras forças, tais como, condições meteorológicas (variações diárias de temperatura e umidade relativa do ar) que começam a agir sobre os materiais constituintes das estruturas desde o momento da construção e durante toda sua vida útil. Nesse contexto, definiu-se como meta dessa pesquisa investigar a resposta deformacional de construções de alvenaria frente aos estímulos provocados por diferentes níveis de vibração e pressão acústica gerados pelo desmonte de rochas com explosivos em diferentes condições geológicas, comparando-as com os efeitos das variações climáticas de temperatura e umidade. Visando o atendimento desta demanda, a resposta de três estruturas, duas residenciais e uma comercial, a diferentes operações com desmonte de rochas (mineração de carvão e pedreira) foram avaliadas. A movimentação das paredes de estruturas de alvenaria, comumente encontradas no entorno de empreendimentos mineiros, foi registrada com sensores de velocidade instalados nas paredes e os resultados foram correlacionados com os níveis de vibração no terreno e pressão acústica (ruído) na atmosfera que provocaram esta movimentação. A partir dos resultados das medições da movimentação das estruturas, deformações induzidas nas paredes, geradas durante trações no plano e flexões fora do plano das paredes, foram computadas e comparadas com os limites de ruptura do material mais fraco que constitui as paredes das estruturas. Em conjunto com o monitoramento da movimentação das estruturas, variações na abertura de rachaduras existentes no reboco no interior ou exterior das estruturas induzidas por forças dinâmicas (detonações) e estática (variações climáticas) foram registradas por meio de sensores de deslocamento instalados em ambos lados das rachaduras. As respostas das estruturas apresentaram excelente acoplamento da fundação com o terreno e nenhuma movimentação livre (ressonância) das paredes das estruturas foi observada após a passagem das ondas sísmicas, indicando que as estruturas seguem muito perto as excitações provocadas pelas vibrações no terreno do terreno e param de movimentar junto com o mesmo. Devido às ondas sísmicas e acústicas atingirem quase que ao mesmo tempo as estruturas, foi difícil separar a influência de cada estímulo. As deformações calculadas foram inferiores as necessárias para induzir rachaduras na argamassa utilizada como reboco nas paredes, considerada como o material mais frágil dentre os constituintes das paredes das estruturas. A resposta deformacional das rachaduras frente às variações climáticas diárias de temperatura e humidade relativa do ar foi superior as variações resultantes da influência das vibrações geradas pelas detonações.
Blasting near residential areas has become frequent in many locations throughout Brazil. Activities related to mining and in especial blasting have become a problem as they generate a potential nuisance to nearby communities resulting from high air sound pressure levels and can result in claims of wall cracking associated with ground vibrations. It was deemed necessary to have a better understanding of how structures of typical national construction respond to blast vibrations and compare this response to other forces, such as, environmental forces that naturally act on these structures since the moment they are constructed and throughout the entire life of the structure. The response of three structures, two residential and one office building, to different blasting activities (coal and quarry blasting) were evaluated in this study. Whole structure motions and the movement of existing cracks were measured in masonry built structures commonly found near mining operations. Whole structure and mid-wall motions were measured at upper and lower corners and on mid-walls using single-axis velocity transducers and compared with ground motions and air sound pressure excitations, measured next to the structures using a tri-axial geophone and microphone. Dynamic (blast-induced) and static (weather-induced) changes in crack width of existing interior and exterior wall cracks in the cement grout, typically used as wall coverage, were recorded. Dynamic structure and crack motions during blasting were time-correlated with ground vibrations and air sound pressure levels. Wall strains generated during out-of plane bending and in-plane tensile strains were computed and compared with the failure strains for the weakest material comprising the wall construction. Long-term crack movement with variations in temperature and humidity were compared with blast-induce peak crack displacements. The structures response showed good coupling of the foundations with the ground and no free-response was observed after the cessations of the ground excitations, indicating the structures are rigid following very close the ground excitation. Because air sound pressure levels and ground motions arrived at the same time in the structures, it was difficult to separate the influence of each stimulus. Calculated strains were lower than the required to induce cracks in the cement grout and environmental-induced crack response, resultant from daily changes in temperature and humidity, were greater than the response caused by blast-induced ground motions and air sound pressure levels in crack aperture.

The first part sets the stage, providing trends on public investment in France, Germany, Italy and Spain. It is preceded by an initial chapter by Rocco Luigi Bubbico, Philipp-Bastian Brutscher and Debora Revoltella from the European Investment Bank (EIB) outlining the experience of Europe as a whole. The picture is as follows: between 2008 and 2016 public investment in the EU declined from 3.4% of GDP to 2.7%. Despite a slight rebound in 2017 and 2018, public investment still stands at only 2.9% of GDP, 15% below its pre-crisis levels. Fiscal consolidation pressure was at the core of such decline in public investment especially in countries that experienced a strong pressure to tighten their budgets. The negative effect of fiscal consolidation was in many cases amplified by a re-prioritization of public outlays away from investment towards current expenditures. Infrastructure investment was disproportionately affected by the decline in public investment. EIB estimates show that overall infrastructure investment declined by about 25% between 2008 and 2016, with the government sector accounting for the lion’s share of this fall. From a sectorial perspective, investment in transport and education infrastructure experienced the strongest decline. The chapter clearly documents that the fall in government infrastructure investment does not reflect a saturation effect, the annual infrastructure investment gap is estimated to be about €155 bn and that construction of new infrastructure seems to continue to produce large positive economic spillover effects. This chapter advises, as a policy lesson, sound project selection: preparation and implementation are the keys to reversing the negative trend in investment activities in the EU, besides overcoming funding constraints. Obviously, to ensure the efficient use of available funds, sound infrastructure governance is also a key factor.

While some years ago the focus of many Groupware systems has been on the support of Web based information systems to support access with Web browsers, the focus today is shifting towards a programmatic access to software services, regardless of their location and the application used to manipulate those services. Whereas the goal of Web Computing has been to support group work on the Web (browser), Web services support for Groupware has the goal to provide interoperability between many Groupware systems. The contribution of this chapter is threefold: (1) to present a framework consisting of three levels of Web services for Groupware support, (2) to present a novel Web services management and configuration architecture with the aim of integrating various Groupware systems in one overall configurable architecture, and (3) to provide a use case scenario and preliminary proof -of-concept implementation. Our overall goal for this chapter is to provide a sound and flexible architecture for gluing together various Groupware systems using Web services technologies.

Surface engineering includes augmentation of intrinsic properties of the boundary of the component, which isolates the continuum from surroundings known as the surface. Two main purposes of surface engineering encapsulate primarily the hardness of the surface for enhanced wear resistance and also to poise up with inter-surface frictional behavior. Today, there are many different surface engineering techniques available: starting from vacuum to atmospheric pressure, wet to dry, simple to sophisticated, and low-cost to high-cost to obtain the required purposeful distinctiveness of material. Most methods used today are dry and thus environmentally sound. This chapter describes various types of coatings over materials to get an overall idea of the technique keeping prime focus on graduate and undergraduate students.

There are a lot of prospects of the vehicular network, including the artificial neural networks incorporating a wireless sensor network. Its number comes after the mobile communication network and the internet. The network is characterized by more through measure and sense and exhibits more comfortable operability and intelligence. A wireless sensor network can be simply defined as “a network of wireless devices using sensors to monitors and recording the physical conditions of the environment and organizing the collected data at a central location.” WSNs measure environmental conditions like temperature, sound, pollution levels, humidity, wind speed and direction, pressure, etc. Thus, wireless sensor networks are widely used for fulfilling the essential needs of environmental sensing applications. These applications show the broad ranges in precision agriculture, monitoring of the vehicle, and video surveillance.

This chapter provides an introduction to Process Synthesis. Sections 7.1 and 7.2 discuss the components of a chemical process system and define the process synthesis problem. Section 7.3 presents the different approaches in the area of process synthesis. Section 7.4 focuses on the optimization approach and discusses modeling issues. Finally, Section 7.5 outlines application areas which are the subject of discussion in chapters 8, 9 and 10. Process Synthesis, an important research area within chemical process design, has triggered during the last three decades a significant amount of academic research work and industrial interest. Extensive reviews exist for the process synthesis area as well as for special classes of problems (e.g., separation systems, heat recovery systems) and for particular approaches (e.g., insights-based approach, optimization approach) applied to process synthesis problems. These are summarized in the following: Overall Process Synthesis: Hendry et al. (1973) Hlavacek(1978) Westerberg (1980) Stephanopoulos (1981) Nishida et al. (1981) Westerberg (1989) Gundersen(1991) Heat Exchanger Network Synthesis: Gundersen and Naess (1988) Separation System Synthesis: Westerberg (1985) Smith and Linnhoff( 1988) Optimization in Process Synthesis: Grossmann (1985), (1989), (1990) Floquet et al. (1988) Grossmann et al. (1987) Floudas and Grossmann (1994) Prior to providing the definition of the process synthesis problem we will describe first the overall process system and its important subsystems. This description can be addressed to the overall process system or individual subsystems and will be discussed in the subsequent sections. An overall process system can be represented as an integrated system that consists of three main interactive components : (i) Chemical plant, (ii) Heat recovery system, (iii) Utility system. In the chemical plant, the transformation of the feed streams (e.g., raw materials) into desired products and possible by-products takes place. In the heat recovery system, the hot and cold process streams of the chemical plant exchange heat so as to reduce the hot and cold utility requirements. In the utility plant, the required utilities (e.g., electricity and power to drive process units) are provided to the chemical plant while hot utilities (e.g., steam at different pressure levels) are provided to the heat recovery system.

<i>Abstract.</i>—Fluvial threat assessments characterize the potential for fluvial habitat conditions to be degraded by differing types and intensities of anthropogenic activities occurring on the landscape, ultimately affecting stream biota. We present a threat assessment for fluvial habitats in Alaska based on six anthropogenic disturbance indices representing urbanization, agriculture/timber harvest, stream fragmentation, point-source pollution, infrastructure, and mines. These indices were combined to develop an overall index of contemporary threat of habitat alteration throughout Alaska using the 12-digit U.S. Geological Survey hydrologic unit code (HUC-12) framework (<i>n </i>= 13,997) and at a finer spatial resolution using local and network catchments for individual stream reaches within Southeast Alaska (<i>n </i>= 207,092). Overall, contemporary threat of habitat alteration indices showed that ~96% of fluvial habitats both statewide and for Southeast Alaska were at low or very low levels; however, anadromous fish habitats were under greater human pressure with nearly double the amount of moderately to severely disturbed habitats when compared to all fluvial habitats. We further evaluated potential future threats to fluvial habitats from mineral mining activities and climate change. More than 86% of existing mine claims statewide and 99% of claims in Southeast Alaska occur in areas of low and very low contemporary threat to fluvial habitats for anadromous fishes. Under climate change, July air temperatures are projected to increase ~1.9°C, on average, by mid-century within HUC-12s containing anadromous fish streams, indicating immense potential to warm streams with anadromous fishes within the state. This fluvial threat assessment demonstrates that overall threats from contemporary anthropogenic disturbance factors are generally low with localized areas of high intensity. However, future threats from mining and climate change have considerable potential to alter fluvial habitats for anadromous fishes in Alaska, particularly those currently unaltered by anthropogenic disturbances.

This paper discusses the potential of using porous ceramic lining as insulating material in combustion chambers with respect to their sound absorbent ability to suppress thermoacoustic instabilities. For this purpose a combustion chamber test rig was developed and different types of ceramic linings were tested. The examined range of power was between 40 and 250 kW and the air-propane equivalence ratio was between 1.2 and 2.0. The overall sound pressure level and frequency domain of a lean premixed swirl stabilized and piloted burner are presented. The resonance frequencies and sound pressure levels are obtained and compared for the different combustion chamber linings. The results show a significant decrease in overall sound pressure level by up to 23.5 dB for sound absorbent lining in comparison to the common sound reflecting combustion chamber lining. In summary, sound absorbent ceramic combustion chamber lining can contribute to improve the stability of lean premixed gas turbines.

Growing environmental sound concerns and recognition that lengthy unprotected exposure to high industrial noise levels can be detrimental to man have resulted in increased attention to reducing industrial noise. In the United States, it is required by law that all turbomachinery manufacturers must provide acoustic guarantees to their customers. For instance, for majority of generators, the near field sound pressure level is usually guaranteed not to exceed 85 dBA. To accomplish this goal, a number of methods of noise reduction have been developed in power industry. As one of the most practical and cost-effective solutions, acoustic blankets have been designed and tested for using on large size electric generators to efficiently reduce their sound pressure levels. This work has successfully demonstrated the potential of acoustic blankets for improve the passive acoustic transmission characteristics from generators. The acoustic data obtained from a field test have shown that the blankets can reduce the overall sound pressure level from large size generators about 4 to 6 dBA.

We study the flow and the aerodynamic sound generated from the wing-tip using numerical analysis. The objective of this study is to clarify the contribution to level of sound generated from the wing-tip. We predicted the aerodynamic sound by the separation method based on Lighthill analogy. The model is a rectangular wing having NACA0012 profiles. The shape of wing-tip is blunt, which has sharp edges. The Reynolds number based on the chord length and uniform velocity is 2×105. The angle of attack is 9 degree which is the lifting condition. The flow around the airfoil is predicted by Large-eddy simulation of turbulent incompressible flow. Current results indicated that the simulated surface pressure distribution and pressure power spectrum agreed quantitatively with measured data. In this result, we calculated the Lighthill tensor from velocity and density of air. In addition we discussed the wing-tip vortex structure and its origin. The far field sound predicted by Lighthill tensor shows a similar tendency to the measured data. To investigate the contribution of the overall level around the airfoil with wing-tip, the far field sound was predicted by Lighthill tensor only around wing-tip. The aerodynamic sound level generated from wing-tip is small compared to the overall level of the sound all around airfoil, however it remains possible that contribute to particular frequency band.

Three-dimensional structures and unsteady nature of vortical flow fields in a half ducted propeller fan have been investigated by a detached eddy simulation (DES) based on k-ω two-equation turbulence model. The validity of the numerical simulation performed in the present study was demonstrated by the comparison to LDV measurement results. The simulation shows the tip vortex is so strong that it dominates the flow field near the rotor tip. The tip vortex does not impinge on the pressure surface of the adjacent blade directly, however it interacts with the shroud surface and induces a separation vortex on the shroud. Furthermore, this separation vortex interacts with the pressure surface of the adjacent blade. These flow structures cause high pressure fluctuation on the shroud surface and the blade pressure surface. Besides, sound pressure levels were predicted by Ffowcs William-Hawkings equation based on Lighthill’s acoustic analogy using the unsteady surface pressure data obtained by DES. As a result, the degree of contribution by each flow structure to overall sound has been estimated quantitatively.

A global description of the intrinsic instabilities of shear layer for further understanding of the aeroacoustical oscillation of subsonic flow over open cavities has been given in the companion paper. The needs to suppress dynamic pressure loads in open cavities play an important role in many aeronautical applications. Large eddy simulation (LES) of passive control methods including recessed leading edge step and sloping trailing edge wall arrangements is performed. The unsteady flow characteristics and aeroacoustical oscillation mechanism of baseline cavity are given in advance. Effects of both passive control methods on resonant frequency and sound pressure levels are demonstrated and analyzed. Recessed leading edge step tends to decrease the resonant Strouhal numbers and the maximal reduction of overall sound pressure levels (OASPL) reaches 8.5dB. Sloping trailing edge wall reduces OASPL by shifting down the impinging location on cavity back wall. The optimal reduction of OASPL arrives at 11dB when the angle of inclination is maximal. The drag induced by cavity flows is found to be highly correlated with dynamic loads on cavity walls.

The effect of airfoil clocking (stator-stator interaction) on efficiency and noise of low pressure turbines (LPT) was investigated experimentally in a multistage turbine high-speed rig. The rig consisted of three stages of a state-of-the-art LPT. The stages were characterized by a very high wall-slope angle, reverse cut-off design, very high lift and very high aspect ratio airfoils. The rig had identical blade count for the second and third stators. The circumferential position of the second stator was individually adjusted with respect to the third stator. Eight different circumferential clocking locations over one pitch were back-to-back tested. The rig was heavily instrumented with miniature five hole probes, hot wires, hot films, total pressure and temperature rakes, pressure tappings on the airfoil surface, two array of Kulites in a rotatory module, etc. Every clocking location was tested with the same instrumentation and at the same operating conditions with the intention of determining the impact of the clocking on the overall efficiency and noise. Due to the large amount of data, the results of this test will be reported in several papers. The present paper contains the impact on the overall efficiency, radial traverses, static pressure fields on the airfoils and averaged sound pressure levels in the duct. The comparison of the results suggests that the efficiency is weakly affected by clocking; however the effect on noise is noticeable for some acoustic tones at certain operating conditions.

A numerical investigation of unsteady flow field and flow induced noise frequency characteristics of a 2-D NACA0018 airfoil taking into account the airfoil’s deformation with different angles of attack is presented. The large eddy simulation (LES) method is employed to compute the unsteady flow field, the dynamic response of structure is simulated with finite element code, and the two different fields are coupled via a two way coupling method with the exchange of pressure and displacement. The far field sound levels and frequency features are calculated using FW-H equation with arbitrary boundary movement involved. The flow field results show that flow separation and wall pressure fluctuation are controlled by the deformation of flexible airfoil significantly, which indicates the effects of attack angle are attenuated. Compared with common quasi-periodic vortex shedding, the vortex shedding at 0 degree is obtained to be a restrict periodic process, and the shedding frequency is about 950Hz, and this phenomenon is confirmed both by wall pressure fluctuation and acoustic spectrum characteristics. In addition, the overall sound pressure levels in chordwise and normal direction are influenced by attack angle in different ways.

During the past decade tightened safety and health regulations concerning noise pollution in the work place have led to an increased importance of acoustic emissions in machinery. In the course of widespread R&D efforts internal combustion engines have received much attention, leading to their optimization and therefore to a higher contribution of hydraulic components, especially pumps and motors, to the overall machinery sound level. However, hydraulic industrial design engineering has only recently begun to take acoustic issues into account at an early design stage. This may be due to the situation that the simulation of sound radiation of complex (hydraulic) machinery is not yet as far developed as other finite element analysis (FEA) fields. In order to improve the sound emission of a variable displacement hydraulic swash plate motor, this paper deals with its acoustic simulation. Therefore an acoustic FEA model is presented. This paper mainly addresses the simulation model setup, the derivation of the resulting dynamic loads and the acoustic analysis, which includes the calculation of the surrounding acoustical near and far field. The simulated sound pressure levels are compared with experimental sound measurements conducted on the motor. Additionally, the influence of different valve plate designs is analyzed.

This work deals with the prediction of noise generated by gas turbines, which includes engines being designed. One has in mind the fulfillment of the ever-increasing concerns with environment, in particular noise. Analytical and empirical methods have been focused by researchers and industry, although only empirical prediction methods are utilized in this work, for the calculation of the one-third octave band sound pressure levels associated to the main engine noise sources. The methodology for the calculation of the engine noise has been combined with performance and design computational programs to evaluate the noise emitted by each engine component and, by proper combination, the engine total noise. A newly designed and manufactured 5 kN/1.2 MW turbojet engine serves as the basis for the noise prediction. For the study, the main noise sources are: compressor, combustor, turbine and propelling nozzle. In terms of the overall sound pressure level, OASPL, are compatible with the noise produced by similar engines. The noise predictions are performed at engine design speeds in the range of 100% down to 70% of the design speed (28,150 rpm). The engine has not run yet, but it is expected that measured noise will be available in the near future. However, it is important to emphasize that all prediction models used to evaluate the radiated noise from the engine were validated. The engine operating conditions were calculated using a high fidelity engine simulator developed to provide the data used in this study. The methods to estimate the one-third octave band sound pressure levels are reported in NASA TM-195480, SAE ARP-876D, NASA-ANOPP and ESDU Item 98019. No atmospheric attenuation and ground reflection were considered in this work.

Noise in large high voltage induction motors (500Hp and above) may be windage or magnetic in nature. Usually large high voltage induction motors induction motors are custom built and tailored to meet customers demand. In large high speed induction motors sometimes it is difficult to isolate windage noise from magnetic noise as the generated frequencies are similar in magnitude; hence reducing noise after motor is manufactured becomes extremely challenging. This paper will present the noise troubleshooting case study of 10,000Hp induction motor that shows overall noise of 100 dB during the factory testing. A variety of tests (e.g unloaded, variable speed, coupled loaded test and also test motor driven as load) were performed to isolate magnetic noise from air borne noise. Noise FFT data was collected to identify peak noise generating frequencies. Sound intensity and sound pressure data were also collected to calculate overall sound power level. After identifying the cause of noise, motor frame design was modified which results in overall noise level of 85 dB.

In 2015, the Natural Sounds and Night Skies Division (NSNSD) received a request to collect baseline acoustical data at Mesa Verde National Park (MEVE). Between July and August 2015, as well as February and March 2016, three acoustical monitoring systems were deployed throughout the park, however one site (MEVE002) stopped recording after a couple days during the summer due to wildlife interference. The goal of the study was to establish a baseline soundscape inventory of backcountry and frontcountry sites within the park. This inventory will be used to establish indicators and thresholds of soundscape quality that will support the park and NSNSD in developing a comprehensive approach to protecting the acoustic environment through soundscape management planning. Additionally, results of this study will help the park identify major sources of noise within the park, as well as provide a baseline understanding of the acoustical environment as a whole for use in potential future comparative studies. In this deployment, sound pressure level (SPL) was measured continuously every second by a calibrated sound level meter. Other equipment included an anemometer to collect wind speed and a digital audio recorder collecting continuous recordings to document sound sources. In this document, “sound pressure level” refers to broadband (12.5 Hz–20 kHz), A-weighted, 1-second time averaged sound level (LAeq, 1s), and hereafter referred to as “sound level.” Sound levels are measured on a logarithmic scale relative to the reference sound pressure for atmospheric sources, 20 μPa. The logarithmic scale is a useful way to express the wide range of sound pressures perceived by the human ear. Sound levels are reported in decibels (dB). A-weighting is applied to sound levels in order to account for the response of the human ear (Harris, 1998). To approximate human hearing sensitivity, A-weighting discounts sounds below 1 kHz and above 6 kHz. Trained technicians calculated time audible metrics after monitoring was complete. See Methods section for protocol details, equipment specifications, and metric calculations. Median existing (LA50) and natural ambient (LAnat) metrics are also reported for daytime (7:00–19:00) and nighttime (19:00–7:00). Prominent noise sources at the two backcountry sites (MEVE001 and MEVE002) included vehicles and aircraft, while building and vehicle predominated at the frontcountry site (MEVE003). Table 1 displays time audible values for each of these noise sources during the monitoring period, as well as ambient sound levels. In determining the current conditions of an acoustical environment, it is informative to examine how often sound levels exceed certain values. Table 2 reports the percent of time that measured levels at the three monitoring locations were above four key values.

1.1 Macroeconomic summary Economic recovery has consistently outperformed the technical staff’s expectations following a steep decline in activity in the second quarter of 2020. At the same time, total and core inflation rates have fallen and remain at low levels, suggesting that a significant element of the reactivation of Colombia’s economy has been related to recovery in potential GDP. This would support the technical staff’s diagnosis of weak aggregate demand and ample excess capacity. The most recently available data on 2020 growth suggests a contraction in economic activity of 6.8%, lower than estimates from January’s Monetary Policy Report (-7.2%). High-frequency indicators suggest that economic performance was significantly more dynamic than expected in January, despite mobility restrictions and quarantine measures. This has also come amid declines in total and core inflation, the latter of which was below January projections if controlling for certain relative price changes. This suggests that the unexpected strength of recent growth contains elements of demand, and that excess capacity, while significant, could be lower than previously estimated. Nevertheless, uncertainty over the measurement of excess capacity continues to be unusually high and marked both by variations in the way different economic sectors and spending components have been affected by the pandemic, and by uneven price behavior. The size of excess capacity, and in particular the evolution of the pandemic in forthcoming quarters, constitute substantial risks to the macroeconomic forecast presented in this report. Despite the unexpected strength of the recovery, the technical staff continues to project ample excess capacity that is expected to remain on the forecast horizon, alongside core inflation that will likely remain below the target. Domestic demand remains below 2019 levels amid unusually significant uncertainty over the size of excess capacity in the economy. High national unemployment (14.6% for February 2021) reflects a loose labor market, while observed total and core inflation continue to be below 2%. Inflationary pressures from the exchange rate are expected to continue to be low, with relatively little pass-through on inflation. This would be compatible with a negative output gap. Excess productive capacity and the expectation of core inflation below the 3% target on the forecast horizon provide a basis for an expansive monetary policy posture. The technical staff’s assessment of certain shocks and their expected effects on the economy, as well as the presence of several sources of uncertainty and related assumptions about their potential macroeconomic impacts, remain a feature of this report. The coronavirus pandemic, in particular, continues to affect the public health environment, and the reopening of Colombia’s economy remains incomplete. The technical staff’s assessment is that the COVID-19 shock has affected both aggregate demand and supply, but that the impact on demand has been deeper and more persistent. Given this persistence, the central forecast accounts for a gradual tightening of the output gap in the absence of new waves of contagion, and as vaccination campaigns progress. The central forecast continues to include an expected increase of total and core inflation rates in the second quarter of 2021, alongside the lapse of the temporary price relief measures put in place in 2020. Additional COVID-19 outbreaks (of uncertain duration and intensity) represent a significant risk factor that could affect these projections. Additionally, the forecast continues to include an upward trend in sovereign risk premiums, reflected by higher levels of public debt that in the wake of the pandemic are likely to persist on the forecast horizon, even in the context of a fiscal adjustment. At the same time, the projection accounts for the shortterm effects on private domestic demand from a fiscal adjustment along the lines of the one currently being proposed by the national government. This would be compatible with a gradual recovery of private domestic demand in 2022. The size and characteristics of the fiscal adjustment that is ultimately implemented, as well as the corresponding market response, represent another source of forecast uncertainty. Newly available information offers evidence of the potential for significant changes to the macroeconomic scenario, though without altering the general diagnosis described above. The most recent data on inflation, growth, fiscal policy, and international financial conditions suggests a more dynamic economy than previously expected. However, a third wave of the pandemic has delayed the re-opening of Colombia’s economy and brought with it a deceleration in economic activity. Detailed descriptions of these considerations and subsequent changes to the macroeconomic forecast are presented below. The expected annual decline in GDP (-0.3%) in the first quarter of 2021 appears to have been less pronounced than projected in January (-4.8%). Partial closures in January to address a second wave of COVID-19 appear to have had a less significant negative impact on the economy than previously estimated. This is reflected in figures related to mobility, energy demand, industry and retail sales, foreign trade, commercial transactions from selected banks, and the national statistics agency’s (DANE) economic tracking indicator (ISE). Output is now expected to have declined annually in the first quarter by 0.3%. Private consumption likely continued to recover, registering levels somewhat above those from the previous year, while public consumption likely increased significantly. While a recovery in investment in both housing and in other buildings and structures is expected, overall investment levels in this case likely continued to be low, and gross fixed capital formation is expected to continue to show significant annual declines. Imports likely recovered to again outpace exports, though both are expected to register significant annual declines. Economic activity that outpaced projections, an increase in oil prices and other export products, and an expected increase in public spending this year account for the upward revision to the 2021 growth forecast (from 4.6% with a range between 2% and 6% in January, to 6.0% with a range between 3% and 7% in April). As a result, the output gap is expected to be smaller and to tighten more rapidly than projected in the previous report, though it is still expected to remain in negative territory on the forecast horizon. Wide forecast intervals reflect the fact that the future evolution of the COVID-19 pandemic remains a significant source of uncertainty on these projections. The delay in the recovery of economic activity as a result of the resurgence of COVID-19 in the first quarter appears to have been less significant than projected in the January report. The central forecast scenario expects this improved performance to continue in 2021 alongside increased consumer and business confidence. Low real interest rates and an active credit supply would also support this dynamic, and the overall conditions would be expected to spur a recovery in consumption and investment. Increased growth in public spending and public works based on the national government’s spending plan (Plan Financiero del Gobierno) are other factors to consider. Additionally, an expected recovery in global demand and higher projected prices for oil and coffee would further contribute to improved external revenues and would favor investment, in particular in the oil sector. Given the above, the technical staff’s 2021 growth forecast has been revised upward from 4.6% in January (range from 2% to 6%) to 6.0% in April (range from 3% to 7%). These projections account for the potential for the third wave of COVID-19 to have a larger and more persistent effect on the economy than the previous wave, while also supposing that there will not be any additional significant waves of the pandemic and that mobility restrictions will be relaxed as a result. Economic growth in 2022 is expected to be 3%, with a range between 1% and 5%. This figure would be lower than projected in the January report (3.6% with a range between 2% and 6%), due to a higher base of comparison given the upward revision to expected GDP in 2021. This forecast also takes into account the likely effects on private demand of a fiscal adjustment of the size currently being proposed by the national government, and which would come into effect in 2022. Excess in productive capacity is now expected to be lower than estimated in January but continues to be significant and affected by high levels of uncertainty, as reflected in the wide forecast intervals. The possibility of new waves of the virus (of uncertain intensity and duration) represents a significant downward risk to projected GDP growth, and is signaled by the lower limits of the ranges provided in this report. Inflation (1.51%) and inflation excluding food and regulated items (0.94%) declined in March compared to December, continuing below the 3% target. The decline in inflation in this period was below projections, explained in large part by unanticipated increases in the costs of certain foods (3.92%) and regulated items (1.52%). An increase in international food and shipping prices, increased foreign demand for beef, and specific upward pressures on perishable food supplies appear to explain a lower-than-expected deceleration in the consumer price index (CPI) for foods. An unexpected increase in regulated items prices came amid unanticipated increases in international fuel prices, on some utilities rates, and for regulated education prices. The decline in annual inflation excluding food and regulated items between December and March was in line with projections from January, though this included downward pressure from a significant reduction in telecommunications rates due to the imminent entry of a new operator. When controlling for the effects of this relative price change, inflation excluding food and regulated items exceeds levels forecast in the previous report. Within this indicator of core inflation, the CPI for goods (1.05%) accelerated due to a reversion of the effects of the VAT-free day in November, which was largely accounted for in February, and possibly by the transmission of a recent depreciation of the peso on domestic prices for certain items (electric and household appliances). For their part, services prices decelerated and showed the lowest rate of annual growth (0.89%) among the large consumer baskets in the CPI. Within the services basket, the annual change in rental prices continued to decline, while those services that continue to experience the most significant restrictions on returning to normal operations (tourism, cinemas, nightlife, etc.) continued to register significant price declines. As previously mentioned, telephone rates also fell significantly due to increased competition in the market. Total inflation is expected to continue to be affected by ample excesses in productive capacity for the remainder of 2021 and 2022, though less so than projected in January. As a result, convergence to the inflation target is now expected to be somewhat faster than estimated in the previous report, assuming the absence of significant additional outbreaks of COVID-19. The technical staff’s year-end inflation projections for 2021 and 2022 have increased, suggesting figures around 3% due largely to variation in food and regulated items prices. The projection for inflation excluding food and regulated items also increased, but remains below 3%. Price relief measures on indirect taxes implemented in 2020 are expected to lapse in the second quarter of 2021, generating a one-off effect on prices and temporarily affecting inflation excluding food and regulated items. However, indexation to low levels of past inflation, weak demand, and ample excess productive capacity are expected to keep core inflation below the target, near 2.3% at the end of 2021 (previously 2.1%). The reversion in 2021 of the effects of some price relief measures on utility rates from 2020 should lead to an increase in the CPI for regulated items in the second half of this year. Annual price changes are now expected to be higher than estimated in the January report due to an increased expected path for fuel prices and unanticipated increases in regulated education prices. The projection for the CPI for foods has increased compared to the previous report, taking into account certain factors that were not anticipated in January (a less favorable agricultural cycle, increased pressure from international prices, and transport costs). Given the above, year-end annual inflation for 2021 and 2022 is now expected to be 3% and 2.8%, respectively, which would be above projections from January (2.3% and 2,7%). For its part, expected inflation based on analyst surveys suggests year-end inflation in 2021 and 2022 of 2.8% and 3.1%, respectively. There remains significant uncertainty surrounding the inflation forecasts included in this report due to several factors: 1) the evolution of the pandemic; 2) the difficulty in evaluating the size and persistence of excess productive capacity; 3) the timing and manner in which price relief measures will lapse; and 4) the future behavior of food prices. Projected 2021 growth in foreign demand (4.4% to 5.2%) and the supposed average oil price (USD 53 to USD 61 per Brent benchmark barrel) were both revised upward. An increase in long-term international interest rates has been reflected in a depreciation of the peso and could result in relatively tighter external financial conditions for emerging market economies, including Colombia. Average growth among Colombia’s trade partners was greater than expected in the fourth quarter of 2020. This, together with a sizable fiscal stimulus approved in the United States and the onset of a massive global vaccination campaign, largely explains the projected increase in foreign demand growth in 2021. The resilience of the goods market in the face of global crisis and an expected normalization in international trade are additional factors. These considerations and the expected continuation of a gradual reduction of mobility restrictions abroad suggest that Colombia’s trade partners could grow on average by 5.2% in 2021 and around 3.4% in 2022. The improved prospects for global economic growth have led to an increase in current and expected oil prices. Production interruptions due to a heavy winter, reduced inventories, and increased supply restrictions instituted by producing countries have also contributed to the increase. Meanwhile, market forecasts and recent Federal Reserve pronouncements suggest that the benchmark interest rate in the U.S. will remain stable for the next two years. Nevertheless, a significant increase in public spending in the country has fostered expectations for greater growth and inflation, as well as increased uncertainty over the moment in which a normalization of monetary policy might begin. This has been reflected in an increase in long-term interest rates. In this context, emerging market economies in the region, including Colombia, have registered increases in sovereign risk premiums and long-term domestic interest rates, and a depreciation of local currencies against the dollar. Recent outbreaks of COVID-19 in several of these economies; limits on vaccine supply and the slow pace of immunization campaigns in some countries; a significant increase in public debt; and tensions between the United States and China, among other factors, all add to a high level of uncertainty surrounding interest rate spreads, external financing conditions, and the future performance of risk premiums. The impact that this environment could have on the exchange rate and on domestic financing conditions represent risks to the macroeconomic and monetary policy forecasts. Domestic financial conditions continue to favor recovery in economic activity. The transmission of reductions to the policy interest rate on credit rates has been significant. The banking portfolio continues to recover amid circumstances that have affected both the supply and demand for loans, and in which some credit risks have materialized. Preferential and ordinary commercial interest rates have fallen to a similar degree as the benchmark interest rate. As is generally the case, this transmission has come at a slower pace for consumer credit rates, and has been further delayed in the case of mortgage rates. Commercial credit levels stabilized above pre-pandemic levels in March, following an increase resulting from significant liquidity requirements for businesses in the second quarter of 2020. The consumer credit portfolio continued to recover and has now surpassed February 2020 levels, though overall growth in the portfolio remains low. At the same time, portfolio projections and default indicators have increased, and credit establishment earnings have come down. Despite this, credit disbursements continue to recover and solvency indicators remain well above regulatory minimums. 1.2 Monetary policy decision In its meetings in March and April the BDBR left the benchmark interest rate unchanged at 1.75%.

Macroeconomic Summary Overall inflation (1.61%) and core inflation (excluding food and regulated items) (1.11%) both declined beyond the technical staff’s expectations in the fourth quarter of 2020. Year-end 2021 forecasts for both indicators were revised downward to 2.3% and 2.1%, respectively. Market inflation expectations also fell over this period and suggested inflation below the 3% target through the end of this year, rising to the target in 2022. Downward pressure on inflation was more significant in the fourth quarter than previously projected, indicating weak demand. Annual deceleration among the main groups of the consumer price index (CPI) was generalized and, except for foods, was greater than projected in the October report. The CPI for goods (excluding foods and regulated items) and the CPI for regulated items were subject to the largest decelerations and forecasting discrepancies. In the first case, this was due in part to a greater-than-expected effect on prices from the government’s “VAT-fee day” amid weak demand, and from the extension of some price relief measures. For regulated items, the deceleration was caused in part by unanticipated declines in some utility prices. Annual change in the CPI for services continued to decline as a result of the performance of those services that were not subject to price relief measures, in particular. Although some of the overall decline in inflation is expected to be temporary and reverse course in the second quarter of 2021, various sources of downward pressure on inflation have become more acute and will likely remain into next year. These include ample excesses in capacity, as suggested by the continued and greater-than-expected deceleration in core inflation indicators and in the CPI for services excluding price relief measures. This dynamic is also suggested by the minimal transmission of accumulated depreciation of the peso on domestic prices. Although excess capacity should fall in 2021, the decline will likely be slower than projected in the October report amid additional restrictions on mobility due to a recent acceleration of growth in COVID-19 cases. An additional factor is that low inflation registered at the end of 2020 will likely be reflected in low price adjustments on certain indexed services with significant weight in the CPI, including real estate rentals and some utilities. These factors should keep inflation below the target and lower than estimates from the previous report on the forecast horizon. Inflation is expected to continue to decline to levels near 1% in March, later increasing to 2.3% at the end of 2021 and 2.7% at year-end 2022 (Graph 1.1). According to the Bank’s most recent survey, market analysts expect inflation of 2.7% and 3.1% in December 2021 and 2022, respectively. Expected inflation derived from government bonds was 2% for year-end 2021, while expected inflation based on bonds one year forward from that date (FBEI 1-1 2022) was 3.2%.