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Journal articles on the topic 'Frequency Modulation (FM)'
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1
Hallberg, Örjan, and Olle Johansson. "Melanoma Incidence and Frequency Modulation (FM) Broadcasting." Archives of Environmental Health: An International Journal 57, no. 1 (January 2002): 32–40. http://dx.doi.org/10.1080/00039890209602914.
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Zhang, Jian Bin, Ming Fang Zhu, Yan Ling Ren, and Jian Lu. "Design of Stereo Frequency Modulation Exciter Controlled by Microcontroller." Applied Mechanics and Materials 29-32 (August 2010): 796–801. http://dx.doi.org/10.4028/www.scientific.net/amm.29-32.796.
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A new stereo Frequency Modulation exciter scheme for short-distance wireless communication is proposed. It adopts a stereo FM IC BH1415 to transmit audio FM signals, and its transmitting frequency is controlled by microcontroller. The basic principle of phase-locked loop for FM is analyzed, and the audio FM circuit based on BH1415 and the controlling method based on AT89C51 are introduced. Test results indicated that, the audio FM Exciter had simple structure and higher reliability, each parameter can meet the demands of FM broadcasting system, and it has some scalability.
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Vu, Thanh Tung, Hong Hai Hoang, Toan Thang Vu, and Ngoc Tam Bui. "A Displacement Measuring Interferometer Based on a Frequency-Locked Laser Diode with High Modulation Frequency." Applied Sciences 10, no. 8 (April 13, 2020): 2693. http://dx.doi.org/10.3390/app10082693.
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Laser interferometers can achieve a nanometer-order uncertainty of measurements when their frequencies are locked to the reference frequencies of the atom or molecule transitions. There are three types of displacement-measuring interferometers: homodyne, heterodyne, and frequency modulation (FM) interferometers. Among these types of interferometer, the FM interferometer has many advantageous features. The interference signal is a series of time-dependent harmonics of modulation frequency, so the phase shift can be detected accurately using the synchronous detection method. Moreover, the FM interferometer is the most suitable for combination with a frequency-locked laser because both require frequency modulation. In previous research, low modulation frequencies at some tens of kHz have been used to lock the frequency of laser diodes (LDs). The low modulation frequency for the laser source means that the maximum measurement speed of the FM interferometers is limited. This paper proposes a novel contribution regarding the application of a high-frequency modulation for an LD to improve both the frequency stability of the laser source and the measurement speed of the FM interferometer. The frequency of the LD was locked to an I2 hyperfine component at 1 MHz modulation frequency. A high bandwidth lock-in amplifier was utilized to detect the saturated absorption signals of the I2 hyperfine structure and induce the signal to lock the frequency of the LD. The locked LD was then used for an FM displacement measuring interferometer. Moreover, a suitable modulation amplitude that affected the signal-to-noise ratio of both the I2 absorption signal and the harmonic intensity of the interference signal was determined. In order to verify the measurement resolution of the proposed interferometer, the displacement induced by a piezo electric actuator was concurrently measured by the interferometer and a capacitive sensor. The difference of the displacement results was less than 20 nm. To evaluate the measurement speed, the interferometer was used to measure the axial error of a high-speed spindle at 500 rpm. The main conclusion of this study is that a stable displacement interferometer with high accuracy and a high measurement speed can be achieved using an LD frequency locked to an I2 hyperfine transition at a high modulation frequency.
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Tabas, Alejandro, and Katharina von Kriegstein. "Neural modelling of the encoding of fast frequency modulation." PLOS Computational Biology 17, no. 3 (March 3, 2021): e1008787. http://dx.doi.org/10.1371/journal.pcbi.1008787.
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Frequency modulation (FM) is a basic constituent of vocalisation in many animals as well as in humans. In human speech, short rising and falling FM-sweeps of around 50 ms duration, called formant transitions, characterise individual speech sounds. There are two representations of FM in the ascending auditory pathway: a spectral representation, holding the instantaneous frequency of the stimuli; and a sweep representation, consisting of neurons that respond selectively to FM direction. To-date computational models use feedforward mechanisms to explain FM encoding. However, from neuroanatomy we know that there are massive feedback projections in the auditory pathway. Here, we found that a classical FM-sweep perceptual effect, the sweep pitch shift, cannot be explained by standard feedforward processing models. We hypothesised that the sweep pitch shift is caused by a predictive feedback mechanism. To test this hypothesis, we developed a novel model of FM encoding incorporating a predictive interaction between the sweep and the spectral representation. The model was designed to encode sweeps of the duration, modulation rate, and modulation shape of formant transitions. It fully accounted for experimental data that we acquired in a perceptual experiment with human participants as well as previously published experimental results. We also designed a new class of stimuli for a second perceptual experiment to further validate the model. Combined, our results indicate that predictive interaction between the frequency encoding and direction encoding neural representations plays an important role in the neural processing of FM. In the brain, this mechanism is likely to occur at early stages of the processing hierarchy.
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Cho, Chihyun, Hyunji Koo, Jae-Yong Kwon, Joo-Gwang Lee, and Tae-Weon Kang. "Measurement of Analog Modulation Index with a Calibrated Radio Frequency Attenuator." Journal of Electromagnetic Engineering and Science 21, no. 2 (April 30, 2021): 87–94. http://dx.doi.org/10.26866/jees.2021.21.2.87.
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This paper presents a method for the accurate and traceable measurement of the analog modulation index. A calibrated step attenuator was used as the main apparatus because it has a higher dynamic range and lower uncertainty than a spectrum analyzer or an oscilloscope. In amplitude modulation (AM), the modulation index is obtained from the amplitude difference between the carrier and the first sideband, as in the conventional method. The resolution and calibration uncertainties of the step attenuator were propagated to the measurement uncertainty of the modulation index. The uncertainty produced by the impedance mismatch and repeatability was also included. For frequency modulation (FM) and phase modulation (PM), the modulation index, β, was estimated (with the step attenuator) from the spectrum of each sideband through the nonlinear fitting of the Bessel function. Thus, the uncertainty of the fitting process was added to the uncertainty of the measurement. The three modulations, AM, FM, and PM, exhibited an expanded uncertainty (approximately 95% confidence level, k = 2) of 0.372% for 50% nominal depth of the AM, 88.8 Hz for the peak frequency deviation of 10 kHz, and 0.88 mrad for a 0.1 radian modulation index, respectively.
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Shindel, Matthew M., and Eric M. Furst. "Frequency modulated microrheology." Lab on a Chip 15, no. 11 (2015): 2460–66. http://dx.doi.org/10.1039/c5lc00351b.
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Marszal, Jacek, and Roman Salamon. "Distance Measurement Errors in Silent Fm-Cw Sonar with Matched Filtering." Metrology and Measurement Systems 19, no. 2 (January 1, 2012): 321–32. http://dx.doi.org/10.2478/v10178-012-0027-6.
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Distance Measurement Errors in Silent Fm-Cw Sonar with Matched Filtering The secretiveness of sonar operation can be achieved by using continuous frequency-modulated sounding signals with reduced power and significantly prolonged repeat time. The application of matched filtration in the sonar receiver provides optimal conditions for detection against the background of white noise and reverberation, and a very good resolution of distance measurements of motionless targets. The article shows that target movement causes large range measurement errors when linear and hyperbolic frequency modulations are used. The formulas for the calculation of these errors are given. It is shown that for signals with linear frequency modulation the range resolution and detection conditions deteriorate. The use of hyperbolic frequency modulation largely eliminates these adverse effects.
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Chen, Hao, and Jun Hai Guo. "Radar Echo Parameter Estimation Using Sparse Time-Frequency Analysis Method." Applied Mechanics and Materials 543-547 (March 2014): 2229–33. http://dx.doi.org/10.4028/www.scientific.net/amm.543-547.2229.
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The echoes of pulse radar from maneuvering targets are amplitude modulation and frequency modulation (AM-FM) signal. At present, the methods of estimating parameters of AM-FM signal are time-frequency analysis method, empirical mode decomposition and empirical wavelet transform based adaptive data analysis methods. This paper takes the idea of intrinsic mode function in guessing the initial phase, and applies the newly developed sparse time-frequency analysis method in AM-FM signal parameter estimation. Simulation results show that the estimating performance of this method in AM-FM signal is good under different SNR and it has low computational cost, and this method is applicable in target acceleration and velocity estimation.
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Marszal, Jacek, Mariusz Rudnicki, Andrzej Jedel, Roman Salamon, and Iwona Kochańska. "Mutual Clutter Suppression Techniques for FM Sonars." Archives of Acoustics 41, no. 4 (December 1, 2016): 721–29. http://dx.doi.org/10.1515/aoa-2016-0069.
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AbstractThe article presents methods that help in the elimination of mutual clutter as well as the consequences of two FM sounding signal sonars operating in the same body of water and frequency band. An in-depth analysis of mutual clutter was carried out. The effects of sounding signal differentiation were determined, as was the Doppler effect on mutual clutter suppression. One of the methods analysed is of particular interest in a situation in which collaborating sonars are operating in opposite frequency modulation directions. This method is effective for both linear and hyperbolic frequency modulations. A formula was derived, identifying exactly how much quantities of clutter may be lessened. The work included comprehensive computer simulations and measurements as well as tests in real-life conditions.
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Schafer, Erin C., Danielle Bryant, Katie Sanders, Nicole Baldus, Katherine Algier, Audrey Lewis, Jordan Traber, Paige Layden, and Aneeqa Amin. "Fitting and Verification of Frequency Modulation Systems on Children with Normal Hearing." Journal of the American Academy of Audiology 25, no. 06 (June 2014): 529–40. http://dx.doi.org/10.3766/jaaa.25.6.3.
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Background: Several recent investigations support the use of frequency modulation (FM) systems in children with normal hearing and auditory processing or listening disorders such as those diagnosed with auditory processing disorders, autism spectrum disorders, attention-deficit hyperactivity disorder, Friedreich ataxia, and dyslexia. The American Academy of Audiology (AAA) published suggested procedures, but these guidelines do not cite research evidence to support the validity of the recommended procedures for fitting and verifying nonoccluding open-ear FM systems on children with normal hearing. Documenting the validity of these fitting procedures is critical to maximize the potential FM-system benefit in the abovementioned populations of children with normal hearing and those with auditory-listening problems. Purpose: The primary goal of this investigation was to determine the validity of the AAA real-ear approach to fitting FM systems on children with normal hearing. The secondary goal of this study was to examine speech-recognition performance in noise and loudness ratings without and with FM systems in children with normal hearing sensitivity. Research Design: A two-group, cross-sectional design was used in the present study. Study Sample: Twenty-six typically functioning children, ages 5–12 yr, with normal hearing sensitivity participated in the study. Intervention: Participants used a nonoccluding open-ear FM receiver during laboratory-based testing. Data Collection and Analysis: Participants completed three laboratory tests: (1) real-ear measures, (2) speech recognition performance in noise, and (3) loudness ratings. Four real-ear measures were conducted to (1) verify that measured output met prescribed-gain targets across the 1000–4000 Hz frequency range for speech stimuli, (2) confirm that the FM-receiver volume did not exceed predicted uncomfortable loudness levels, and (3 and 4) measure changes to the real-ear unaided response when placing the FM receiver in the child’s ear. After completion of the fitting, speech recognition in noise at a –5 signal-to-noise ratio and loudness ratings at a +5 signal-to-noise ratio were measured in four conditions: (1) no FM system, (2) FM receiver on the right ear, (3) FM receiver on the left ear, and (4) bilateral FM system. Results: The results of this study suggested that the slightly modified AAA real-ear measurement procedures resulted in a valid fitting of one FM system on children with normal hearing. On average, prescriptive targets were met for 1000, 2000, 3000, and 4000 Hz within 3 dB, and maximum output of the FM system never exceeded and was significantly lower than predicted uncomfortable loudness levels for the children. There was a minimal change in the real-ear unaided response when the open-ear FM receiver was placed into the ear. Use of the FM system on one or both ears resulted in significantly better speech recognition in noise relative to a no-FM condition, and the unilateral and bilateral FM receivers resulted in a comfortably loud signal when listening in background noise. Conclusions: Real-ear measures are critical for obtaining an appropriate fit of an FM system on children with normal hearing.
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Wilson, Adam S., Joseph W. Hall, and John H. Grose. "Detection of frequency modulation (FM) in the presence of a second FM tone." Journal of the Acoustical Society of America 88, no. 3 (September 1990): 1333–38. http://dx.doi.org/10.1121/1.399710.
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Sheft, Stanley, Min-Yu Cheng, and Valeriy Shafiro. "Discrimination of Stochastic Frequency Modulation by Cochlear Implant Users." Journal of the American Academy of Audiology 26, no. 06 (June 2015): 572–81. http://dx.doi.org/10.3766/jaaa.14067.
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Background: Past work has shown that low-rate frequency modulation (FM) may help preserve signal coherence, aid segmentation at word and syllable boundaries, and benefit speech intelligibility in the presence of a masker. Purpose: This study evaluated whether difficulties in speech perception by cochlear implant (CI) users relate to a deficit in the ability to discriminate among stochastic low-rate patterns of FM. Research Design: This is a correlational study assessing the association between the ability to discriminate stochastic patterns of low-rate FM and the intelligibility of speech in noise. Study Sample: Thirteen postlingually deafened adult CI users participated in this study. Data Collection and Analysis: Using modulators derived from 5-Hz lowpass noise applied to a 1-kHz carrier, thresholds were measured in terms of frequency excursion both in quiet and with a speech-babble masker present, stimulus duration, and signal-to-noise ratio in the presence of a speech-babble masker. Speech perception ability was assessed in the presence of the same speech-babble masker. Relationships were evaluated with Pearson product–moment correlation analysis with correction for family-wise error, and commonality analysis to determine the unique and common contributions across psychoacoustic variables to the association with speech ability. Results: Significant correlations were obtained between masked speech intelligibility and three metrics of FM discrimination involving either signal-to-noise ratio or stimulus duration, with shared variance among the three measures accounting for much of the effect. Compared to past results from young normal-hearing adults and older adults with either normal hearing or a mild-to-moderate hearing loss, mean FM discrimination thresholds obtained from CI users were higher in all conditions. Conclusions: The ability to process the pattern of frequency excursions of stochastic FM may, in part, have a common basis with speech perception in noise. Discrimination of differences in the temporally distributed place coding of the stimulus could serve as this common basis for CI users.
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Han, Yao, and Kai Yu Qin. "The Implementation of In-Band FM Based on Fractional-N PLL." Advanced Materials Research 889-890 (February 2014): 869–74. http://dx.doi.org/10.4028/www.scientific.net/amr.889-890.869.
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This paper studied the in-band frequency modulation technology based on fractional-N PLL, first elaborated the basic principle and transfer function analysis of FM PLL, and according to the fractional-N theory gives the realization principle and the concrete algorithm of the modulation signal frequency in the loop modulation loop bandwidth of PLL, gives the design of key circuit, and the result shows that the technology can realize the frequency of modulation signal low to the DC, and high precision modulation, good frequency stability.
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Luo, Huan, Yadong Wang, David Poeppel, and Jonathan Z. Simon. "Concurrent Encoding of Frequency and Amplitude Modulation in Human Auditory Cortex: Encoding Transition." Journal of Neurophysiology 98, no. 6 (December 2007): 3473–85. http://dx.doi.org/10.1152/jn.00342.2007.
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Complex natural sounds (e.g., animal vocalizations or speech) can be characterized by specific spectrotemporal patterns the components of which change in both frequency (FM) and amplitude (AM). The neural coding of AM and FM has been widely studied in humans and animals but typically with either pure AM or pure FM stimuli. The neural mechanisms employed to perceptually unify AM and FM acoustic features remain unclear. Using stimuli with simultaneous sinusoidal AM (at rate fAM = 37 Hz) and FM (with varying rates ƒFM), magnetoencephalography (MEG) is used to investigate the elicited auditory steady-state response (aSSR) at relevant frequencies (ƒAM, ƒFM, ƒAM + fFM). Previous work demonstrated that for sounds with slower FM dynamics ( fFM < 5 Hz), the phase of the aSSR at ƒAM tracked the FM; in other words, AM and FM features were co-tracked and co-represented by “phase modulation” encoding. This study explores the neural coding mechanism for stimuli with faster FM dynamics (≤30 Hz), demonstrating that at faster rates ( fFM > 5 Hz), there is a transition from pure phase modulation encoding to a single-upper-sideband (SSB) response (at frequency fAM + fFM) pattern. We propose that this unexpected SSB response can be explained by the additional involvement of subsidiary AM encoding responses simultaneously to, and in quadrature with, the ongoing phase modulation. These results, using MEG to reveal a possible neural encoding of specific acoustic properties, demonstrate more generally that physiological tests of encoding hypotheses can be performed noninvasively on human subjects, complementing invasive, single-unit recordings in animals.
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Atencio, Craig A., David T. Blake, Fabrizio Strata, Steven W. Cheung, Michael M. Merzenich, and Christoph E. Schreiner. "Frequency-Modulation Encoding in the Primary Auditory Cortex of the Awake Owl Monkey." Journal of Neurophysiology 98, no. 4 (October 2007): 2182–95. http://dx.doi.org/10.1152/jn.00394.2007.
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Many communication sounds, such as New World monkey twitter calls, contain frequency-modulated (FM) sweeps. To determine how this prominent vocalization element is represented in the auditory cortex we examined neural responses to logarithmic FM sweep stimuli in the primary auditory cortex (AI) of two awake owl monkeys. Using an implanted array of microelectrodes we quantitatively characterized neuronal responses to FM sweeps and to random tone-pip stimuli. Tone-pip responses were used to construct spectrotemporal receptive fields (STRFs). Classification of FM sweep responses revealed few neurons with high direction and speed selectivity. Most neurons responded to sweeps in both directions and over a broad range of sweep speeds. Characteristic frequency estimates from FM responses were highly correlated with estimates from STRFs, although spectral receptive field bandwidth was consistently underestimated by FM stimuli. Predictions of FM direction selectivity and best speed from STRFs were significantly correlated with observed FM responses, although some systematic discrepancies existed. Last, the population distributions of FM responses in the awake owl monkey were similar to, although of longer temporal duration than, those in the anesthetized squirrel monkeys.
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Shore, K. A., and D. M. Kane. "Optimum modulation frequency for FM seeded FSF laser ranging." IEE Proceedings - Optoelectronics 153, no. 6 (December 1, 2006): 284–86. http://dx.doi.org/10.1049/ip-opt:20060035.
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Casseday, John H., Ellen Covey, and Benedikt Grothe. "Neural Selectivity and Tuning for Sinusoidal Frequency Modulations in the Inferior Colliculus of the Big Brown Bat, Eptesicus fuscus." Journal of Neurophysiology 77, no. 3 (March 1, 1997): 1595–605. http://dx.doi.org/10.1152/jn.1997.77.3.1595.
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Casseday, John H., Ellen Covey, and Benedikt Grothe. Neural selectivity and tuning for sinusoidal frequency modulations in the inferior colliculus of the big brown bat, Eptesicus fuscus. J. Neurophysiol. 77: 1595–1605, 1997. Most communication sounds and most echolocation sounds, including those used by the big brown bat ( Eptesicus fuscus), contain frequency-modulated (FM) components, including cyclical FM. Because previous studies have shown that some neurons in the inferior colliculus (IC) of this bat respond to linear FM sweeps but not to pure tones or noise, we asked whether these or other neurons are specialized for conveying information about cyclical FM signals. In unanesthetized bats, we tested the response of 116 neurons in the IC to pure tones, noise with various bandwidths, single linear FM sweeps, sinusoidally amplitude-modulated signals, and sinusoidally frequency-modulated (SFM) signals. With the use of these stimuli, 20 neurons (17%) responded only to SFM, and 10 (9%) responded best to SFM but also responded to one other test stimulus. We refer to the total 26% of neurons that responded best to SFM as SFM-selective neurons. Fifty-nine neurons (51%) responded about equally well to SFM and other stimuli, and 27 (23%) did not respond to SFM but did respond to other stimuli. Most SFM-selective neurons responded to a limited range of modulation rates and a limited range of modulation depths. The range of modulationrates over which individual neurons responded was 5–170 Hz( n = 20). Thus SFM-selective neurons respond to low modulation rates. The depths of modulations to which the neurons responded ranged from ±0.4 to ±19 kHz ( n = 15). Half of the SFM-selective neurons did not respond to the first cycle of SFM. This finding suggests that the mechanism for selective response to SFM involves neural delays and coincidence detectors in which the response to one part of the SFM cycle coincides in time either with the response to a later part of the SFM cycle or with the response to the first part of the next cycle. The SFM-selective neurons in the IC responded to a lower and more limited range of SFM rates than do neurons in the nuclei of the lateral lemniscus of this bat. Because the FM components of biological sounds usually have low rates of modulation, we suggest that the tuning of these neurons is related to biologically important sound parameters. The tuning could be used to detect FM in echolocation signals, modulations in high-frequency sounds that are generated by wing beats of some beetles, or social communication sounds of Eptesicus.
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Godey, Benoit, Craig A. Atencio, Ben H. Bonham, Christoph E. Schreiner, and Steven W. Cheung. "Functional Organization of Squirrel Monkey Primary Auditory Cortex: Responses to Frequency-Modulation Sweeps." Journal of Neurophysiology 94, no. 2 (August 2005): 1299–311. http://dx.doi.org/10.1152/jn.00950.2004.
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The squirrel monkey twitter call is an exemplar of a broad class of species-specific vocalizations that contain naturally voiced frequency-modulated (FM) sweeps. To investigate how this prominent communication call element is represented in primary auditory cortex (AI), neuronal receptive field properties to pure-tone and synthetic, logarithmically spaced FM-sweep stimuli in 3 barbiturate-anesthetized squirrel monkeys are studied. Responses to pure tones are assessed by using standard measures of frequency response areas, whereas responses to FM sweeps are classified according to direction selectivity, best speed, and speed tuning preferences. Most neuronal clusters respond to FM sweeps in both directions and over a range of FM speeds. Center frequencies calculated from the average of high and low trigger frequency edges of FM response profiles are highly correlated with pure-tone characteristic frequencies (CFs). However, bandwidth estimates are only weakly correlated with their pure-tone counterparts. CF and direction selectivity are negatively correlated. Best speed maps reveal idiosyncratically positioned spatial aggregation of similar values. In contrast, direction selectivity maps show unambiguous spatial organization. Neuronal clusters selective for upward-directed FM sweeps are located in ventral–caudal AI, where CFs range from 0.5 to 1 kHz. Combinations of pure-tone and FM response parameters form 2 significant factors to account for response variations. These results are interpreted in the context of earlier FM investigations and neuronal encoding of dynamic sounds.
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Luo, Huan, Yadong Wang, David Poeppel, and Jonathan Z. Simon. "Concurrent Encoding of Frequency and Amplitude Modulation in Human Auditory Cortex: MEG Evidence." Journal of Neurophysiology 96, no. 5 (November 2006): 2712–23. http://dx.doi.org/10.1152/jn.01256.2005.
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A natural sound can be described by dynamic changes in envelope (amplitude) and carrier (frequency), corresponding to amplitude modulation (AM) and frequency modulation (FM), respectively. Although the neural responses to both AM and FM sounds are extensively studied in both animals and humans, it is uncertain how they are corepresented when changed simultaneously but independently, as is typical for ecologically natural signals. This study elucidates the neural coding of such sounds in human auditory cortex using magnetoencephalography (MEG). Using stimuli with both sinusoidal modulated envelope (ƒAM, 37 Hz) and carrier frequency (ƒFM, 0.3–8 Hz), it is demonstrated that AM and FM stimulus dynamics are corepresented in the neural code of human auditory cortex. The stimulus AM dynamics are represented neurally with AM encoding, by the auditory steady-state response (aSSR) at ƒAM. For sounds with slowly changing carrier frequency (ƒFM <5 Hz), it is shown that the stimulus FM dynamics are tracked by the phase of the aSSR, demonstrating neural phase modulation (PM) encoding of the stimulus carrier frequency. For sounds with faster carrier frequency change (ƒFM ≥ 5 Hz), it is shown that modulation encoding of stimulus FM dynamics persists, but the neural encoding is no longer purely PM. This result is consistent with the recruitment of additional neural AM encoding over and above the original neural PM encoding, indicating that both the amplitude and phase of the aSSR at ƒAM track the stimulus FM dynamics. A neural model is suggested to account for these observations.
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Robson, Stephen, Gan Tan, and Abderrahmane Haddad. "Low-Cost Monitoring of Synchrophasors Using Frequency Modulation." Energies 12, no. 4 (February 15, 2019): 611. http://dx.doi.org/10.3390/en12040611.
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A new, low-cost method of simultaneously measuring and communicating voltage and current on distribution networks is presented. Based on Frequency Modulation (FM) of the measured fundamental frequency (and harmonics), followed by immediate re-injection of the modulated waveform back into the network, the proposed method can be implemented using inexpensive and readily available electronics. Furthermore, the method does not require a separate communication media, but instead uses the power line itself to propagate the FM signals back to a central point. EMTP-ATP simulations on a mixed LV/MV network are performed and experimental analysis demonstrates the practicality and robustness of the new method. The low-cost of the method would suit deployment on parts of the network which are otherwise overlooked for monitoring.
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Lewis, M. Samantha, Carl C. Crandell, Michael Valente, and Jane Enrietto Horn. "Speech Perception in Noise: Directional Microphones versus Frequency Modulation (FM) Systems." Journal of the American Academy of Audiology 15, no. 06 (June 2004): 426–39. http://dx.doi.org/10.3766/jaaa.15.6.4.
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The major consequence of sensorineural hearing loss (SNHL) is communicative difficulty, especially with the addition of noise and/or reverberation. The purpose of this investigation was to compare two types of technologies that have been shown to improve the speech-perception performance of individuals with SNHL: directional microphones and frequency modulation (FM) systems. Forty-six adult subjects with slight to severe SNHL served as subjects. Speech perception was assessed using the Hearing in Noise Test (HINT) with correlated diffuse noise under five different listening conditions. Results revealed that speech perception was significantly better with the use of the FM system over that of any of the hearing aid conditions, even with the use of the directional microphone. Additionally, speech perception was significantly better with the use of two hearing aids used in conjunction with two FM receivers rather than with just one FM receiver. Directional microphone performance was significantly better than omnidirectional microphone performance. All aided listening conditions were significantly better than the unaided listening condition.
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Fu, Ziying, Na Xu, Guimin Zhang, Dandan Zhou, Long Liu, Jia Tang, Philip Hung-Sun Jen, and Qicai Chen. "Evoked potential study of the inferior collicular response to constant frequency-frequency modulation (CF-FM) sounds in FM and CF-FM bats." Journal of Comparative Physiology A 205, no. 2 (March 22, 2019): 239–52. http://dx.doi.org/10.1007/s00359-019-01326-4.
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Nespor, Amy A., Robert J. Dooling, and Jeffrey D. Triblehorn. "Detection of frequency modulation (FM) and amplitude modulation (AM) by budgerigars (Melopsittacus undulatus)." Journal of the Acoustical Society of America 100, no. 4 (October 1996): 2753. http://dx.doi.org/10.1121/1.416902.
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Buss, Emily, Crystal N. Taylor, and Lori J. Leibold. "Factors Affecting Sensitivity to Frequency Change in School-Age Children and Adults." Journal of Speech, Language, and Hearing Research 57, no. 5 (October 2014): 1972–82. http://dx.doi.org/10.1044/2014_jslhr-h-13-0254.
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Purpose The factors affecting frequency discrimination in school-age children are poorly understood. The goal of the present study was to evaluate developmental effects related to memory for pitch and the utilization of temporal fine structure. Method Listeners were 5.1- to 13.6-year-olds and adults, all with normal hearing. A subgroup of children had musical training. The task was a 3-alternative forced choice in which listeners identified the interval with the higher frequency tone or the tone characterized by frequency modulation (FM). The standard was 500 or 5000 Hz, and the FM rate was either 2 or 20 Hz. Results Thresholds tended to be higher for younger children than for older children and adults for all conditions, although this age effect was smaller for FM detection than for pure-tone frequency discrimination. Neither standard frequency nor modulation rate affected the child/adult difference FM thresholds. Children with musical training performed better than their peers on pure-tone frequency discrimination at 500 Hz. Conclusions Testing frequency discrimination using a low-rate FM detection task may minimize effects related to cognitive factors like memory for pitch or training effects. Maturation of frequency discrimination does not appear to differ across conditions in which listeners are hypothesized to rely on temporal cues and place cues.
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Kumar, Rajendra. "Analysis of FM demodulator output noise with applications to FM telemetry." Journal of Applied Mathematics and Decision Sciences 2006 (July 5, 2006): 1–13. http://dx.doi.org/10.1155/jamds/2006/53649.
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We present an analysis for evaluating the probability density function (pdf) of the noise at the output of the frequency demodulator. It is shown that the noise is non-Gaussian and that for low to medium signal-to-noise power ratios, its pdf differs very significantly from the Gaussian pdf commonly assumed in simplified analysis. These results are very important for analyzing the performance of the PCM/FM type of modulation schemes used in telemetry systems as illustrated in the paper.
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Bartsch, Eva, and Sabine Schmidt. "Psychophysical frequency modulation thresholds in a FM-bat, Tadarida brasiliensis." Hearing Research 67, no. 1-2 (May 1993): 128–38. http://dx.doi.org/10.1016/0378-5955(93)90240-2.
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Moore, Brian C. J., Sashi Mariathasan, and Aleksander P. Sęk. "Effects of Age and Hearing Loss on the Discrimination of Amplitude and Frequency Modulation for 2- and 10-Hz Rates." Trends in Hearing 23 (January 2019): 233121651985396. http://dx.doi.org/10.1177/2331216519853963.
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Detection of frequency modulation (FM) with rate = 10 Hz may depend on conversion of FM to amplitude modulation (AM) in the cochlea, while detection of 2-Hz FM may depend on the use of temporal fine structure (TFS) information. TFS processing may worsen with greater age and hearing loss while AM processing probably does not. A two-stage experiment was conducted to test these ideas while controlling for the effects of detection efficiency. Stage 1 measured psychometric functions for the detection of AM alone and FM alone imposed on a 1-kHz carrier, using 2- and 10-Hz rates. Stage 2 assessed the discrimination of AM from FM at the same modulation rate when the detectability of the AM alone and FM alone was equated. Discrimination was better for the 2-Hz than for the 10-Hz rate for all young normal-hearing subjects and for some older subjects with normal hearing at 1 kHz. Other older subjects with normal hearing showed no clear difference in AM-FM discrimination for the 2- and 10-Hz rates, as was the case for most older hearing-impaired subjects. The results suggest that the ability to use TFS cues is reduced for some older people and most hearing-impaired people.
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Liu, Lu Lu, Chuan Liang Li, Ying Fa Wu, Wei Xin Shi, Fei Long Wu, Xuan Bing Qiu, and Ji Lin Wei. "The Application of a High Sensitive Laser Frequency Modulation Absorption Specroscopy." Applied Mechanics and Materials 675-677 (October 2014): 336–40. http://dx.doi.org/10.4028/www.scientific.net/amm.675-677.336.
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Due to the weak absorption of H2O in the near infra red region, the frequency modulation (FM) is one of good technologies to increase the sensitivity of detection. This method is used to study the absorption spectra of water-vapor in the region around 814.65 nm. Compared to direct absorption method, the signal-to-noise of spectral signal is enhanced. Therefore, the laser FM is a good potential spectroscopic technology in the application of laser sensor for trace gas.
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Vatti, Marianna, Sébastien Santurette, Niels Henrik Pontoppidan, and Torsten Dau. "Perception of a Sung Vowel as a Function of Frequency-Modulation Rate and Excursion in Listeners With Normal Hearing and Hearing Impairment." Journal of Speech, Language, and Hearing Research 57, no. 5 (October 2014): 1961–71. http://dx.doi.org/10.1044/2014_jslhr-h-13-0219.
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Purpose Frequency fluctuations in human voices can usually be described as coherent frequency modulation (FM). As listeners with hearing impairment (HI listeners) are typically less sensitive to FM than listeners with normal hearing (NH listeners), this study investigated whether hearing loss affects the perception of a sung vowel based on FM cues. Method Vibrato maps were obtained in 14 NH and 12 HI listeners with different degrees of musical experience. The FM rate and FM excursion of a synthesized vowel, to which coherent FM was applied, were adjusted until a singing voice emerged. Results In NH listeners, adding FM to the steady vowel components produced perception of a singing voice for FM rates between 4.1 and 7.5 Hz and FM excursions between 17 and 83 cents on average. In contrast, HI listeners showed substantially broader vibrato maps. Individual differences in map boundaries were, overall, not correlated with audibility or frequency selectivity at the vowel fundamental frequency, with no clear effect of musical experience. Conclusion Overall, it was shown that hearing loss affects the perception of a sung vowel based on FM-rate and FM-excursion cues, possibly due to deficits in FM detection or discrimination or to a degraded ability to follow the rate of frequency changes.
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She, Fang Yi, Jian Hua Kang, Fang Zheng Yang, and Chao Xu. "Testing Method Discussion of FM Simulcast System." Applied Mechanics and Materials 602-605 (August 2014): 1868–73. http://dx.doi.org/10.4028/www.scientific.net/amm.602-605.1868.
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This paper introduces the development of FM simulcast, as well as the specific implementation methods and requirements of FM simulcast system for "Triple Same" and "One Guarantee". Finally, this paper takes the same frequency overlay network of JingJinTang highway as example, furthermore, details the FM simulcast system how to accomplish the testing of the same frequency, the same modulation, the same phase and cover the field strength.
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Lewis, M. Samantha, Carl C. Crandell, and Nicole V. Kreisman. "Effects of Frequency Modulation (FM) Transmitter Microphone Directivity on Speech Perception in Noise." American Journal of Audiology 13, no. 1 (June 2004): 16–22. http://dx.doi.org/10.1044/1059-0889(2004/004).
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Frequency modulation (FM) technology can significantly improve the speech perception ability of individuals with sensorineural hearing loss (SNHL) in background noise. Previous investigations have demonstrated that the microphone design of the FM transmitter can have a significant impact on this improved speech perception. The purpose of this investigation was to compare 3 types of FM transmitter microphone designs: (a) wide angle (omnidirectional microphone), which amplifies sounds coming from all directions around the microphone equally; (b) zoom (1 directional microphone), which provides less amplification to signals coming from the rear, and (c) superzoom (2 directional microphones), which provides less amplification to signals originating from the rear and the sides. Fifteen adults with bilateral slight to moderately severe SNHL participated. Speech perception was assessed using the Hearing in Noise Test (M. Nilsson, S. Soli, & J. Sullivan, 1994). Speech spectrum shaped noise served as the noise competition. Results revealed that the best speech perception in noise was obtained when the FM transmitter was used in the zoom setting. The poorest performance was obtained when the FM transmitter was in the wide-angle mode. The clinical implications of these results are discussed.
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Bertachini, Ana Lívia Libardi, Altair Cadrobbi Pupo, Marina Morettin, Maria Angelina Nardi Martinez, Maria Cecília Bevilacqua, Adriane Lima Mortari Moret, Sheila Andreoli Balen, and Regina Tangerino de Souza Jacob. "Frequency Modulation System and speech perception in the classroom: a systematic literature review." CoDAS 27, no. 3 (June 2015): 292–300. http://dx.doi.org/10.1590/2317-1782/20152014103.
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PURPOSE: This review aimed at presenting the benefits regarding the speech perception in noise shown by children who wear hearing aid devices and/or cochlear implants with the Frequency Modulation (FM) System at school. RESEARCH STRATEGY: A bibliographic survey was conducted in an electronic database with standardized search until the year 2012, and a manual search was performed by using specific keywords. SELECTION CRITERIA: For the selection and evaluation of the scientific studies chosen in the search, criteria were established covering the following aspects: type of study, participants, adopted intervention, and evaluation of results. DATA ANALYSIS: The FM system was verified to improve speech perception and speech threshold in noise in all studies. RESULTS: Regarding the performance as to type, the best results were obtained when children used the personal FM system, followed by the table and the sound field systems. CONCLUSION: After extensive review of national and international literature, it was concluded that the studies indicate the need for further research concerning mainly the impact of the FM system on the school performance of children who have sensory devices coupled to the FM system. Findings in the literature with relation to the publications focused on speech perception in noise did not relate educational and auditory aspects.
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Ge, Qian, Qian Wang, Xiao Yan, and Ling He. "Algorithms for Automatic Modulation Recognition in Wireless Monitoring Applications." Applied Mechanics and Materials 241-244 (December 2012): 1772–78. http://dx.doi.org/10.4028/www.scientific.net/amm.241-244.1772.
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The paper proposes an automatic modulation recognition scheme based on instantaneous features of intercepted signals. The modulation classifier can discriminate modulations such as Amplitude Modulation (AM), Double Side Band (DSB), Single Side Band (SSB), Frequency Modulation (FM), M-ary Amplitude Shift Keying (M-ASK), M-ary Frequency Shift Keying (M-FSK), M-ary Phase Shift Keying (M-PSK) and M-ary Quadrature Amplitude Modulation (M-QAM) without any prior information. The scheme is with simple structure, computationally simpler, and suitable for real-time processing. And the recognition parameters are anti-noise, and insensitive to frequency offset, phase offset and timing error. To evaluate the performance of the scheme, several experiments with signals in Additive White Gaussian Noise (AWGN) channel were carried out in the MATLAB by varying the values of both the main modulation parameters and the signal-to-noise ratios (SNRs). The results show that the approach can achieve high recognition accuracy even at low SNR.
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BERNHARDT, PAUL A. "COMMUNICATIONS USING CHAOTIC FREQUENCY MODULATION." International Journal of Bifurcation and Chaos 04, no. 02 (April 1994): 427–40. http://dx.doi.org/10.1142/s0218127494000289.
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Chaotic Frequency Modulation (CFM) provides the basis for a nonlinear communications system with (1) good noise suppression and (2) analogue signal encryption for private and secure communications links. CFM is a generalization of conventional Wideband Frequency Modulation (WFM) where the information about modulation samples mk are contained in the lengths of the periods pk for the kth cycle of the WFM waveform. A WFM modulator produces waveform periods described by an invertible function of the form pk=F(mk). Chaotic FM uses a map of the pulse periods to produce a noise-like pulse train even with a constant signal. The basis for CFM is a function pk=F(mk; pk−1, pk−2, …, pk−i), where i is the dimensionality of the map. A practical realization for a CFM transmitter employs an autonomous chaotic relaxation oscillator (ACRO) circuit for use as a chaotic voltage-controlled oscillator (CVCO). The ACRO is simple to construct, consisting of only two capacitors, one inductor, a bistable nonlinear element, and a modulated current source. The CVCO period (pk) is a nonlinear function of the current (mk) and the two previous pulse periods. Demodulation requires the use of at least three successive waveform-periods. Experimental and theoretical studies of the CVCO circuit have shown that (1) the ACRO return maps of pulse periods are embedded in three dimensions, (2) chaotic outputs are difficult to decode without prior knowledge of the circuit parameters, and (3) demodulation may be accomplished with a digital signal processor.
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Su, Yang, Qing Hao Wang, Bo Liu, Hai Nan Su, Yan Hai Huang, Jian Guo Xu, Yun Guo Wu, Li Jie Bei, Xin Nan Xie, and Xiao Liu. "The Partial Discharge Test of Transformer Using Frequency Modulation Type Series Resonance Method." Applied Mechanics and Materials 543-547 (March 2014): 705–8. http://dx.doi.org/10.4028/www.scientific.net/amm.543-547.705.
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Traditional frequency power and test equipment cannot meet the requirements. This paper discusses in detail the composition of FM type series resonance test device, technical principles, characteristics and advantages. And also introduces wiring method, test methods, test standard. The instance proves that discharge test of large transformer using the FM series resonance device is convenient and accurate.
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Ding, Nai, and Jonathan Z. Simon. "Neural Representations of Complex Temporal Modulations in the Human Auditory Cortex." Journal of Neurophysiology 102, no. 5 (November 2009): 2731–43. http://dx.doi.org/10.1152/jn.00523.2009.
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Natural sounds such as speech contain multiple levels and multiple types of temporal modulations. Because of nonlinearities of the auditory system, however, the neural response to multiple, simultaneous temporal modulations cannot be predicted from the neural responses to single modulations. Here we show the cortical neural representation of an auditory stimulus simultaneously frequency modulated (FM) at a high rate, fFM ≈ 40 Hz, and amplitude modulation (AM) at a slow rate, fAM <15 Hz. Magnetoencephalography recordings show fast FM and slow AM stimulus features evoke two separate but not independent auditory steady-state responses (aSSR) at fFM and fAM, respectively. The power, rather than phase locking, of the aSSR of both decreases with increasing stimulus fAM. The aSSR at fFM is itself simultaneously amplitude modulated and phase modulated with fundamental frequency fAM, showing that the slow stimulus AM is not only encoded in the neural response at fAM but also encoded in the instantaneous amplitude and phase of the neural response at fFM. Both the amplitude modulation and phase modulation of the aSSR at fFM are most salient for low stimulus fAM but remain observable at the highest tested fAM (13.8 Hz). The instantaneous amplitude of the aSSR at fFM is successfully predicted by a model containing temporal integration on two time scales, ∼25 and ∼200 ms, followed by a static compression nonlinearity.
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Fukuma, Takeshi. "INVITED PAPER: Instrumentation and Biological Applications of High-Resolution Frequency Modulation Atomic Force Microscopy in Liquid." Journal of Nano Research 4 (January 2009): 1–10. http://dx.doi.org/10.4028/www.scientific.net/jnanor.4.1.
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Frequency modulation atomic force microscopy (FM-AFM) has been a powerful tool for imaging atomic-scale structures and properties of various materials including metals, semiconductors, metal oxides, alkali halides and organic systems. Whilst the method has been used mainly in ultrahigh vacuum environments, recent progress in FM-AFM instrumentation made it possible to apply this technique also to investigations in liquid. This technological innovation opened up a variety of applications of FM-AFM in biology and electrochemistry. To date, the improved FM-AFM instrument and technique have been applied to investigations of several biological materials, providing novel information that has not been accessible with other imaging techniques. In this review, I will summarize the recent progress in FM-AFM instrumentation and biological applications in liquid.
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Cabrera, Laurianne, and Judit Gervain. "Speech perception at birth: The brain encodes fast and slow temporal information." Science Advances 6, no. 30 (July 2020): eaba7830. http://dx.doi.org/10.1126/sciadv.aba7830.
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Speech perception is constrained by auditory processing. Although at birth infants have an immature auditory system and limited language experience, they show remarkable speech perception skills. To assess neonates’ ability to process the complex acoustic cues of speech, we combined near-infrared spectroscopy (NIRS) and electroencephalography (EEG) to measure brain responses to syllables differing in consonants. The syllables were presented in three conditions preserving (i) original temporal modulations of speech [both amplitude modulation (AM) and frequency modulation (FM)], (ii) both fast and slow AM, but not FM, or (iii) only the slowest AM (<8 Hz). EEG responses indicate that neonates can encode consonants in all conditions, even without the fast temporal modulations, similarly to adults. Yet, the fast and slow AM activate different neural areas, as shown by NIRS. Thus, the immature human brain is already able to decompose the acoustic components of speech, laying the foundations of language learning.
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Ma, Zong Min, Ji Liang Mu, Jun Tang, Hui Xue, Huan Zhang, Chen Yang Xue, Jun Liu, and Yan Jun Li. "Artifacts in KPFM in FM, AM and Heterodyne AM Modes." Key Engineering Materials 609-610 (April 2014): 1362–68. http://dx.doi.org/10.4028/www.scientific.net/kem.609-610.1362.
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In this paper, the crosstalk in potential measurements caused by the topographic feedback and the resonance frequency in Kelvin probe force microscopy (KPFM) was investigated in frequency modulation (FM), amplitude modulation (AM) and heterodyne amplitude modulation (heterodyne AM) modes. We showed theoretically that the distance-dependence of the modulated electrostatic force in AM-KPFM is significantly weaker than in FM-and heterodyne AM-KPFMs. We experimentally confirmed that the crosstalk in FM-KPFM and heterodyne AM-KPFM is weak than that in AM-KPFM due to the bigger difference of the modulated frequencies in topographic and potential measurements in FM and heterodyne AM-KPFMs. We also compared the corrugations in the local contact potential difference (LCPD) on the surface of Si (001) show that difference on topographic (potential) images is approximately 15 pm (10 mV) between the faulted and unfaulted parts using heterodyne AM-KPFM, on the other hand, this difference cannot be observed using AM-KPFM mode. Original of this was attributed to the low crosstalk between the topographic and the LCPD measurements in heterodyne AM-KPFM.
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Jacob, Regina Tangerino de Souza, Tacianne Kriscia Machado Alves, Adriane Lima Mortari Moret, Marina Morettin, Larissa Germiniani dos Santos, and Maria Fernanda Capoani Garcia Mondelli. "Participation in regular classroom of student with hearing loss: frequency modulation System use." CoDAS 26, no. 4 (July 2014): 308–14. http://dx.doi.org/10.1590/2317-1782/201420130027.
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PURPOSE: Translate and adapt to Portuguese the Classroom Participation Questionnaire (CPQ) and compare the participation in regular classroom of students with hearing impairment with and without the use of frequency modulation (FM) System.METHODS: The translation and adaptation of CPQ included the translation into Portuguese, linguistic adaptation and review of grammatical and idiomatic equivalences. The questionnaire was administered to 15 children and teenagers using hearing aids (HA) and/or cochlear implant (CI), fitted with personal FM System.RESULTS: The translation of the English CPQ into the Portuguese instrument resulted in the "Questionário de participação em sala de aula" with the same number of questions as the original version; regarding linguistic adaptation, no difficulty was observed in the understanding of the items proposed in the application for students with hearing loss.CONCLUSION: The CPQ instrument was translated and culturally adapted for the Brazilian population, being named "Questionário de participação em sala de aula"in the Portuguese version. The study contributes to observation and monitoring of participation in regular classroom of students with hearing impairment using FM System. In general, students reported increased confidence and participation in the classroom with the use of FM System.
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Бочаров, М. И., and А. В. Володько. "CONTROLLED GENERATORS ON SAW FILTERS AND OF SYNTHESIZED NONLINEAR INDUCTANCE." ВЕСТНИК ВОРОНЕЖСКОГО ГОСУДАРСТВЕННОГО ТЕХНИЧЕСКОГО УНИВЕРСИТЕТА, no. 5() (November 18, 2020): 114–18. http://dx.doi.org/10.36622/vstu.2020.16.5.017.
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Проведены исследования качественных характеристик однокаскадных частотно-модулированных (ЧМ) генераторов, выполненных на однокаскадном усилителе по схеме с общим коллектором и узкополосным фильтром на поверхностных акустических волнах (ПАВ) при использовании в качестве управителя частоты синтезированной нелинейной индуктивности (СНИ). Получены расчетные соотношения для определения девиации основной частоты, уровня нелинейных искажений для третьей и пятой гармоник и крутизны модуляционной характеристики, которая практически постоянна как при перестройке генератора по частоте, так и изменении уровня модулирующего сигнала. В результате этого в процессе модуляции уровень паразитной амплитудной модуляции не повышается, что обеспечивает высокую частоту спектра формируемого ЧМ радиосигнала. Проведен анализ полученных технических характеристик, который показал, что исследуемый формирователь ЧМ сигнала при управлении напряжением СНИ практически не создает сдвига центральной частоты, который приводит в процессе модуляции к уменьшению стабильности частоты. Установлено, что при девиации основной частоты около 90 кГц коэффициент нелинейных искажений по третьей и пятой гармоникам составляет менее 1 % и 0.1 % соответственно. Это соизмеримо с уровнем нелинейных искажений ЧМ генератора, в котором в качестве управителя частоты используются варакторы с резким законом изменения вольтфарадной характеристики, обеспечивающей минимально возможные нелинейные искажения при модуляции генераторов с помощью варакторов и практически полным отсутствием этих искажений на четных гармониках We investigated qualitative characteristics of the single-stage FM generators made on a single-stage amplifier according to the scheme with a common collector and a narrow-band filter on surface acoustic waves (SAW) using synthesized nonlinear inductance (SNI) as a frequency controller. We obtained the calculated ratios for base frequency deviation, level of nonlinear distortions for third and fifth harmonics and slope of modulation characteristic, which is practically constant both during generator tuning by frequency and change of level of modulating signal. As a result, during modulation, the level of parasitic amplitude modulation does not increase, which provides a high purity of the spectrum of the generated FM radio signal. We carried out an analysis of the obtained technical characteristics, which showed that the FM signal generator under the control of the SNI voltage practically does not create a central frequency shift, which leads to a decrease in frequency stability during modulation. We found that when the main frequency deviates about 90 kHz, the non-linear distortion coefficient for the third and fifth harmonics is less than 1% and 0.1%, respectively. This is comparable to the level of non-linear distortion of the FM generator, in which varactors with a sharp law of changing the voltfarade characteristic are used as a frequency controller, which provides the minimum possible non-linear distortion when modulating generators using varactors and the almost complete absence of these distortions on even harmonics
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O'Neill, William E., and W. Owen Brimijoin. "Directional Selectivity for FM Sweeps in the Suprageniculate Nucleus of the Mustached Bat Medial Geniculate Body." Journal of Neurophysiology 88, no. 1 (July 1, 2002): 172–87. http://dx.doi.org/10.1152/jn.00966.2001.
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Mustached bats emit echolocation and communication calls containing both constant frequency (CF) and frequency-modulated (FM) components. Previously we found that 86% of neurons in the ventral division of the external nucleus of the inferior colliculus (ICXv) were directionally selective for linear FM sweeps and that selectivity was dependent on sweep rate. The ICXv projects to the suprageniculate nucleus (Sg) of the medial geniculate body. In this study, we isolated 37 single units in the Sg and measured their responses to best excitatory frequency (BEF) tones and linear 12-kHz upward and downward FM sweeps centered on the BEF. Sweeps were presented at durations of 30, 12, and 4 ms, yielding modulation rates of 400, 1,000, and 3,000 kHz/s. Spike count versus level functions were obtained at each modulation rate and compared with BEF controls. Sg units responded well to both tones and FM sweeps. BEFs clustered at 58 kHz, corresponding to the dominant CF component of the sonar signal. Spike count functions for both tones and sweeps were predominantly non-monotonic. FM directional selectivity was significant in 53–78% of the units, depending on modulation rate and level. Units were classified as up-selective (52%), down-selective(24%), or bi-directional ( non-selective, 16%); a few units (8%) showed preferences that were either rate-or level-dependent. Most units showed consistent directional preferences at all SPLs and modulation rates tested, but typically showed stronger selectivity at lower sweep rates. Directional preferences were attributable to suppression of activity by sweeps in the non-preferred direction (∼80% of units) and/or facilitation by sweeps in the preferred direction (∼20–30%). Latencies for BEF tones ranged from 4.9 to 25.7 ms. Latencies for FM sweeps typically varied linearly with sweep duration. Most FM latency-duration functions had slopes ranging from 0.4 to 0.6, suggesting that the responses were triggered by the BEF. Latencies for BEF tones and FM sweeps were significantly correlated in most Sg units, i.e., the response to FM was temporally related to the occurrence of the BEF in the FM sweep. FM latency declined relative to BEF latency as modulation rate increased, suggesting that at higher rates response is triggered by frequencies in the sweep preceding the BEF. We conclude that Sg and ICXv units have similar, though not identical, response properties. Sg units are predominantly upsweep selective and could respond to either or both the CF and FM components in biosonar signals in a number of echolocation scenarios, as well as to a variety of communication sounds.
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Schafer, Erin C., Denise Romine, Elizabeth Musgrave, Sadaf Momin, and Christy Huynh. "Electromagnetic versus Electrical Coupling of Personal Frequency Modulation (FM) Receivers to Cochlear Implant Sound Processors." Journal of the American Academy of Audiology 24, no. 10 (November 2013): 927–40. http://dx.doi.org/10.3766/jaaa.24.10.5.
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Background: Previous research has suggested that electrically coupled frequency modulation (FM) systems substantially improved speech-recognition performance in noise in individuals with cochlear implants (CIs). However, there is limited evidence to support the use of electromagnetically coupled (neck loop) FM receivers with contemporary CI sound processors containing telecoils. Purpose: The primary goal of this study was to compare speech-recognition performance in noise and subjective ratings of adolescents and adults using one of three contemporary CI sound processors coupled to electromagnetically and electrically coupled FM receivers from Oticon. Research Design: A repeated-measures design was used to compare speech-recognition performance in noise and subjective ratings without and with the FM systems across three test sessions (Experiment 1) and to compare performance at different FM-gain settings (Experiment 2). Descriptive statistics were used in Experiment 3 to describe output differences measured through a CI sound processor. Study Sample: Experiment 1 included nine adolescents or adults with unilateral or bilateral Advanced Bionics Harmony (n = 3), Cochlear Nucleus 5 (n = 3), and MED-EL OPUS 2 (n = 3) CI sound processors. In Experiment 2, seven of the original nine participants were tested. In Experiment 3, electroacoustic output was measured from a Nucleus 5 sound processor when coupled to the electromagnetically coupled Oticon Arc neck loop and electrically coupled Oticon R2. Data Collection and Analysis: In Experiment 1, participants completed a field trial with each FM receiver and three test sessions that included speech-recognition performance in noise and a subjective rating scale. In Experiment 2, participants were tested in three receiver-gain conditions. Results in both experiments were analyzed using repeated-measures analysis of variance. Experiment 3 involved electroacoustic-test measures to determine the monitor-earphone output of the CI alone and CI coupled to the two FM receivers. Results: The results in Experiment 1 suggested that both FM receivers provided significantly better speech-recognition performance in noise than the CI alone; however, the electromagnetically coupled receiver provided significantly better speech-recognition performance in noise and better ratings in some situations than the electrically coupled receiver when set to the same gain. In Experiment 2, the primary analysis suggested significantly better speech-recognition performance in noise for the neck-loop versus electrically coupled receiver, but a second analysis, using the best performance across gain settings for each device, revealed no significant differences between the two FM receivers. Experiment 3 revealed monitor-earphone output differences in the Nucleus 5 sound processor for the two FM receivers when set to the +8 setting used in Experiment 1 but equal output when the electrically coupled device was set to a +16 gain setting and the electromagnetically coupled device was set to the +8 gain setting. Conclusions: Individuals with contemporary sound processors may show more favorable speech-recognition performance in noise electromagnetically coupled FM systems (i.e., Oticon Arc), which is most likely related to the input processing and signal processing pathway within the CI sound processor for direct input versus telecoil input. Further research is warranted to replicate these findings with a larger sample size and to develop and validate a more objective approach to fitting FM systems to CI sound processors.
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Bakry, Ahmed. "Modeling of Millimeter-Wave Modulation Characteristics of Semiconductor Lasers under Strong Optical Feedback." Scientific World Journal 2014 (2014): 1–9. http://dx.doi.org/10.1155/2014/728458.
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This paper presents modeling and simulation on the characteristics of semiconductor laser modulated within a strong optical feedback (OFB-)induced photon-photon resonance over a passband of millimeter (mm) frequencies. Continuous wave (CW) operation of the laser under strong OFB is required to achieve the photon-photon resonance in the mm-wave band. The simulated time-domain characteristics of modulation include the waveforms of the intensity and frequency chirp as well as the associated distortions of the modulated mm-wave signal. The frequency domain characteristics include the intensity modulation (IM) and frequency modulation (FM) responses in addition to the associated relative intensity noise (RIN). The signal characteristics under modulations with both single and two mm-frequencies are considered. The harmonic distortion and the third order intermodulation distortion (IMD3) are examined and the spurious free dynamic range (SFDR) is calculated.
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Fukuma, Takeshi. "Improvements in fundamental performance of in-liquid frequency modulation atomic force microscopy." Microscopy 69, no. 6 (August 11, 2020): 340–49. http://dx.doi.org/10.1093/jmicro/dfaa045.
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Abstract In-liquid frequency modulation atomic force microscopy (FM-AFM) has been used for visualizing subnanometer-scale surface structures of minerals, organic thin films and biological systems. In addition, three-dimensional atomic force microscopy (3D-AFM) has been developed by combining it with a three-dimensional (3D) tip scanning method. This method enabled the visualization of 3D distributions of water (i.e. hydration structures) and flexible molecular chains at subnanometer-scale resolution. While these applications highlighted the unique capabilities of FM-AFM, its force resolution, speed and stability are not necessarily at a satisfactory level for practical applications. Recently, there have been significant advancements in these fundamental performances. The force resolution was dramatically improved by using a small cantilever, which enabled the imaging of a 3D hydration structure even in pure water and made it possible to directly compare experimental results with simulated ones. In addition, the improved force resolution allowed the enhancement of imaging speed without compromising spatial resolution. To achieve this goal, efforts have been made for improving bandwidth, resonance frequency and/or latency of various components, including a high-speed phase-locked loop (PLL) circuit. With these improvements, now atomic-resolution in-liquid FM-AFM imaging can be performed at ∼1 s/frame. Furthermore, a Si-coating method was found to improve stability and reproducibility of atomic-resolution imaging owing to formation of a stable hydration structure on a tip apex. These improvements have opened up new possibilities of atomic-scale studies on solid-liquid interfacial phenomena by in-liquid FM-AFM.
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LEE, S. R., and S. W. RA. "Variable Cutoff Frequency Pre-Modulation Filter for PCM/FM Transmission System." IEICE Transactions on Communications E91-B, no. 5 (May 1, 2008): 1387–96. http://dx.doi.org/10.1093/ietcom/e91-b.5.1387.
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Schorer, E. "Critical modulation frequency based on detection of AM versus FM tones." Journal of the Acoustical Society of America 79, no. 4 (April 1986): 1054–57. http://dx.doi.org/10.1121/1.393377.
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NAKAJIMA, Hideo, Akinori KOGURE, and Shiho MORIGUCHI. "Evaluation of Solid-Liquid Interfaces by Frequency Modulation AFM (FM-AFM)." Journal of The Surface Finishing Society of Japan 72, no. 3 (March 1, 2021): 150–53. http://dx.doi.org/10.4139/sfj.72.150.
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Yang, Zhang Cheng, and Xiang Lin Wang. "Analysis on Anti-Noise Performance of Frequency Modulation System Based on MATLAB Simulation." Applied Mechanics and Materials 543-547 (March 2014): 2426–30. http://dx.doi.org/10.4028/www.scientific.net/amm.543-547.2426.
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The popularity of internet technology has brought the change very big to the life and production of modern humans, the current Internet technology application has penetrated into people in every aspect of modern life, has become an indispensable part of people's life. Firstly, system model of the current network communication to dissect, analyzes the architecture of network communication system, modulation and demodulation principle is applied to design the FM communication signal modulation system network communication in the Internet technology, the non coherent demodulation method to build FM demodulation system, realize the demodulation process through differential device, the anti noise performance of the method of frequency modulation system of MATLAB simulation experiments, the experimental results show that the method of anti noise performance significantly, to a certain extent, provide theoretical basis and technical support for the research in this field.
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Noskov, V. Ya, E. V. Bogatyrev, K. A. Ignatkov, and K. D. Shaidurov. "Features of the Formation and Processing of Signals in an Autodyne Radar with Frequency Modulation Taking into Account the Nonlinearity of the Modulation Characteristic." Ural Radio Engineering Journal 5, no. 2 (2021): 119–43. http://dx.doi.org/10.15826/urej.2021.5.1.003.
Full textAbstract:
The results of the study of the features of the formation and processing of signals of autodyne short-range radar systems (SRR) with frequency modulation (FM) involving non-linearity of the modulation characteristic are presented. The numerical simulation of the nonlinear influence of the modulation characteristic on the shape and spectrum of the autodyne signal is implemented on the basis of the mathematical model of the autodyne generator. We have established that even a small non-linearity of this characteristic causes a significant distortion of the shape and spectrum of the autodyne signal. A method of quasi-static correction of the law of frequency modulation of probing radiation using a digital signal processor is proposed, which does not require complication of the microwave part of the autodyne SRR with FM. The results of experimental studies of an 8-mm autodyne SRR made on the basis of a Gann diode oscillator with frequency control by varicap are presented.