bluuebunny/crossref_metadata_2025 huggingface dataset:
Detecting the clicks of beaked whales with wavelets.
Authors: Fischer Mark
Published: October 2009

Most of the algorithms used for classifying cetaceans by call operate by analyzing acoustic data displayed by spectrographic analysis. Because spectrograms are based on Fourier transforms, this standardized technique works well at classifying the frequency modulated calls that Fourier transforms are most capable of illuminating. This includes the whistles and rhythmic pulses produced by many whale species. By contrast, the foraging clicks of Ziphidae consist almost entirely of exceedingly short duration, wide frequency, and fast-repeating click trains. Fourier-based algorithms provide a clumsy tool at best to interpret such transient data. Using the results of wavelet transforms with certain types of data, especially transient data, can vastly improve the task of classifying Ziphidae clicks. By calibrating the scales of individual transforms, wavelets can also be fine-tuned to provide a better match with particular kinds of clicks. The result of this optimization process is called a “wavelet profile,” the combination of a wavelet transform with a range of scales matched to the clicks of a particular species. This paper explains a process for tuning and programming the selection of such profiles. The objective of this work is to suggest a better method for automatically classifying the calls of the cetacean species.
Automatic detection of marine mammals using spectral entropy.
Authors: Erbe Christine
Published: October 2009

An automatic detector for tonal and narrow-band signals of a variety of co-habiting marine mammal species is presented. The detector was developed to automatically identify signals in years of autonomous underwater recordings made in the Arctic. These recordings contained calls of odontocetes, mysticetes, and pinnipeds. Three types of automatic detectors were tested; two were based on peak-energy detection, and one was based on spectral entropy computation. A set of test data was assembled by active listening and visual discrimination of spectrograms. Performances of the automatic detectors were compared by means of receiver operating characteristics. The entropy detector outperformed the other two. It ran considerably faster than real time and can be used as a first step in automatic signal analysis, quickly scanning recordings for potential signals. It should be followed by automatic classification, recognition, and identification algorithms to group and identify signals.
Effects of seismic exploration in the Beaufort Sea on bowhead whale call distributions.
Authors: Nations Christopher S. , Blackwell Susanna B. , Kim Katherine H. , Thode Aaron M. , Greene Charles R. , Macrander A. Michael , McDonald Trent L.
Published: October 2009

We analyzed locations of bowhead whale (Balaena mysticetus) calls in the Beaufort Sea during the fall migrations of 2007 and 2008, including periods of seismic exploration. Analysis examined relationships between received sound levels from airgun pulses and both spatial and temporal distributions of whale call locations. Locations were estimated by triangulation of calls received on Directional Autonomous Seafloor Acoustic Recorders (DASARs) arranged in five arrays along 280 km of Alaska’s coast. Received levels either were measured directly by DASARs or estimated from transmission loss equations. For analysis, a grid was overlaid on the study region, and the 7-week study period was divided into short, regular intervals. Whale calls were counted and received levels estimated within each grid cell and time interval. The relationship between call count and received level was assessed using statistical models that accounted for anthropogenic sounds, date, time of day, bathymetry, and east-west position along the coast. Furthermore, the models incorporated adjustments for detectability (DASARs are less likely to detect more distant calls) and spatial and temporal covariances. Preliminary results indicate declines in calling rate and temporary onshore and offshore shifts in location as received levels increase. [Work supported by Shell Exploration and Production Company.]
Quantifying masking effects of seismic survey reverberation off the Alaskan North Slope.
Authors: Guerra Melania , Thode Aaron M. , Blackwell Susanna B. , Greene Charles R. , Macrander Michael
Published: October 2009

Quantifying the potential impacts of anthropogenic acoustic noise on marine life faces tremendous hurdles, including defining appropriate metrics to be extracted from the raw acoustic data. In shallow Arctic environments, reverberation from seismic arrays can persist over periods longer than the duration of the direct signal, suggesting that reverberation might play a role in masking communication between endemic animals like the bowhead whale (Balaena mysticetus). Presented here is a quantitative metric related to the masking properties of impulsive anthropogenic signals in shallow water environments. The approach taken is to measure the minimum level of the acoustic noise field, where the level is typically defined in terms of rms pressure or sound exposure. Three time scales need to be defined in order to specify the minimum level: the biologically-relevant energy-integration timescale of a species’s hearing mechanism, the time-scale over which the noise signal can be considered wide-sense stationary, and the time-scale over which significant secular changes take place in the source, receiver, or propagation characteristics of a cyclical (multi-pulse) scenario. Examples of this metric are provided using data collected in 2008 from seismic surveys in the Beaufort Sea in 25–50-m depth water. [Work supported by Shell Exploration and Production Company.]
Characterization of pelagic scatterers using multibeam echosounder data: Echo amplitude and phase, and their variabilities and frequency spectra.
Authors: Demer David A. , Cutter George R. , Weber Thomas C. , Wilson Christopher D.
Published: October 2009

A recently-developed statistical-spectral approach to acoustic-target identification (SSID) incorporates information contained in the frequency-dependent signal amplitudes and their variances. In addition to identifying biological targets, the SSID has demonstrated utility for estimating fish aggregation densities, abundances, and behaviors, and detecting and classifying the seabed (e.g., accurate depth, within-beam slope, hardness and roughness, and the height of the unresolved boundary region, and the so-called dead zone). Further, the related multi-frequency, bi-planar, interferometric technique (MBI) allows much higher-resolution measurements of the seabed and sub-beam measures of slope, hardness, and roughness. Here we extend the utilities of the SSID and MBI methods, with explicit consideration of the single-frequency signal phases and their variances, and frequency-dependent split-aperture phases and their variances, for improved estimations of pelagic-target sizes, and their aggregation densities, behaviors, and shapes (e.g., surface rugosity). Data from the Simrad ME70, split-aperture, multibeam echosounder allow these methods to be applied to data collected over a broad bandwidth and range of incidence angles for more classification and observation possibilities.
Variable-aperture processing of multibeam echosounder data to better resolve fish locations and improve abundance estimates.
Authors: Cutter George R. , Demer David A.
Published: October 2009

Acoustic classifications of fish and estimations of their orientation distributions are possible using multi-frequency or broad bandwidth measurements of their acoustic target strengths (TSs) with knowledge of their scattering directivity pattern and size distributions. To measure TS of in situ fish, single-frequency interferometric methods provide information to detect resolvable single targets and estimate their location within the acoustic beam. This technique is compromised by multiple targets that are unresolvable because of their spacing, but this situation can be mitigated with the use of multi-frequency interferometry. The ambiguity caused by coincident echoes can also be substantially reduced using single-frequency, multiple-aperture interferometry. This method uses phase differences from multiple sub-arrays of a single-frequency (200-kHz) multibeam echosounder to estimate robustly when echoes originate from a resolvable single target and its position within the acoustic beams. Results provide accurate measures of beam-compensated TS and, in cases of low-density scatterers, estimates of their volume density. Multiple-aperture interferometry can significantly improve the utility of single-frequency multibeam echosounders for quantitative measures of fish and zooplankton, and seabed-range detections.
Single- and multi-beam echosounder assessment of Antarctic krill aggregations.
Authors: Warren Joseph D. , Cox Martin J. , Demer David A. , Cutter George R. , Brierley Andrew S.
Published: October 2009

Acoustic backscatter measurements from aggregations of Antarctic krill were collected over two field seasons (2006 and 2007) in the waters north of Livingston Island using two 5.5-m inflatable vessels. One was equipped with a dual-frequency (38- and 200-kHz) single-beam echosounder, while the other used a 200-kHz multi-beam system. In addition to independent survey operations, both vessels participated in joint survey operations where the two boats followed the same trackline separated by a small distance (10–40 m). These data allow us to compare how the two echosounder systems “see” the same (or very similar) krill aggregations. During 2006, some tracklines were also occupied by a large (300-ft) vessel although vessel separation distances were larger during these operations. The combination of measurements from single- and multi-beam echosounders (and nearby net tows) provides the opportunity to characterize krill aggregation size, shape, numerical density, and overall biomass. Observations of krill predators were made from both small vessels during these surveys. Results discussing the interactions between krill predators and krill aggregations will be presented.
Scattering properties of a time-evolving multiple scattering elastic medium.
Authors: Sukhovich Alexey , Roux Philippe , Larose Eric
Published: October 2009

We investigate the propagation of Lamb waves in a thin duralumin plate with randomly distributed strong scatterers. Each scatterer is created by rigidly clamping the plate with a screw to a vertical postlocated under the plate. The evolution of the medium properties is created by the time variation of the plate temperature. The basic effect of the temperature variation is the change of both longitudinal and shear sound speeds in the plate due to the change in the elastic moduli of the plate material. Two types of the change in the medium are considered: the global change with slow variation in the overall temperature of the plate and the local change introduced by heating the plate with a point-like heat source. In both cases the change in the medium is quantified by measuring magnitude and time-shift of the cross-correlations between successive signals as a function of temperature. The two changes are expected to have different effects on the wave propagation in the plate and were found to manifest themselves differently. Our preliminary results indicate the possibility of future applications in seismology by allowing characterization of the changes in the wave speed propagation in the earth crust.
Bayesian parameter estimation of porous materials.
Authors: Dieckman Eric A. , Xiang Ning
Published: October 2009

This work proposes a new application of Bayesian analysis to determine the physical parameters of a rigid frame porous material from the measurement of the material’s acoustic impedance. Bayesian analysis allows for numerical estimation of physical parameters, their uncertainties, and inter-relationship of the parameters from the measured complex impedance. Complex impedance data are simulated based on measurements of a sample material to test the Bayesian formulation. Using synthesized data allows for investigations of different frequency resolutions and different levels of noise on the algorithm. Results obtained from testing the parameter estimation algorithm with synthesized data will be utilized in applying the algorithm to measured complex impedance data.
Recent research in musical timbre perception.
Authors: Beauchamp James W. , Horner Andrew B. , Hall Michael D.
Published: October 2009

Various methods have been used in an attempt to reveal salient parameters for musical timbre perception and to estimate perceptual distances between timbres based on their spectra. The multidimensional scaling method compares exemplars of musical sounds using listener estimation of timbral dissimilarity between sound pairs. Data are coalesced into a space whose dimensions are easily interpretable in terms of acoustic parameters such as spectral centroid, spectral flux, spectral irregularity, and attack time. Sounds can be normalized with respect to some parameters in order to reveal others. The direct comparison method attempts to discover how discrimination, recognition, and degree of perceptual dissimilarity depend on the degree of modification of the time-varying spectrum or of particular features of the spectrum. Morphing between spectrum pairs is one method of producing spectral modifications. Dissimilarity can be predicted by computing a “distance” between two time-varying spectra. For musical sounds, spectral distance has been computed by taking the average Cartesian distance between spectral measures treated as vectors. For constant-F0 sounds, the most obvious vector is the set of harmonic amplitudes, either in linear or decibel units. Other vectors are based on critical bands and cepstral coefficients. [Work supported by Research Grants Council Grant No. 613508.]
Psychoacoustics and organology.
Authors: Hajda John M.
Published: October 2009

Organology, a branch of ethnomusicology, is the study of musical instruments and their classification. The first Western system–which classified instruments primarily as idiophones, membranophones, chordophones, or aerophones—was proposed by Sachs and von Hornbostel in 1914. This system has been the progenitor and inspiration for numerous other classification systems. While the van Hornbostel–Sachs system has proven to be useful in many contexts, it does not offer a consistent approach in terms of the transfer of energy from driver to generator to resonator. In addition, it does not take into account the common practice in modern popular and art music by which digitized samples of sounds are disembodied and appropriated from musical instruments from around the world. In other words, rather than encountering musical instruments as visual, tactile, and sound-producing, musicians and audiences encounter only pure sound. This paper, therefore, addresses two issues: How would a classification system of musical instrument {\sound} take into account the vibrational characteristics of acoustical musical instruments as well as the results of perceptual research on musical timbre from the past 40 years? The resulting system effectively turns Hornbostel–Sachs “on its ear” by reinterpreting primary classes as subclasses and vice versa.
Observations of the singing voice during pregnancy. A case study.
Authors: Lã Filipa , Sundberg Johan
Published: October 2009

Previous studies showed a strong correlation between cervical and vocal fold smears [Abitbol et al., J. Voice 13, 424–446 (1999)]. Myers et al. [Eur. J. Obstet. Gynecol. Reprod. Biol. 144S, S82–S89 (2009)] found significant changes in mechanical properties of tissues during pregnancy. This suggests that similar changes may occur also in laryngeal tissues, affecting conditions for vocal fold vibration. Recordings of audio, electrolaryngograph, oral pressure, and air flow signals were made of a professional classically trained soprano once per week, starting on week 28 of pregnancy. The tasks comprised reading a text and singing a song. In addition, the singer repeated the syllable [pae] while performing a diminuendo at various pitches, allowing determination of the lowest pressures producing vocal fold vibration and contact, i.e., the phonation and contact threshold pressures [Enflo and Sundberg (unpublished)]. Oral pressure during the occlusion for the consonant [p] was accepted as an estimate of subglottal pressure. Voice source was analyzed by means of inverse filtering and the relation between this pressure and various voice source parameters was analyzed. Preliminary results of this exploratory study show substantial effects of pregnancy on voice production.
Vibrational modes of nanoparticles studied by ultrafast optical spectroscopy.
Authors: Hartland Gregory V.
Published: October 2009

Excitation of metal nanoparticles with an ultrafast laser pulse causes rapid heating. This can excite the vibrational modes of the particle that correlate with the expansion coordinate. Comparison of the experimentally measured periods to continuum mechanics calculations (usually done through finite element modeling) allows us to assign the observed vibrational modes. In most cases the breathing mode is excited, and its frequency depends on the size, shape, and elastic constants of the particles. For typical particle sizes of tens of nanometers, the frequencies are in the range of 10–100 GHz. A range of different shapes has been studied: spheres, cubes, rods, and even hollow particles. The measured and calculated periods are usually in good agreement, which implies that the elastic constants of small metal particles are similar to the bulk material. Experiments on single metal particles have also been performed. These measurements allow us to determine the damping times of the acoustic vibrational modes, which cannot be done in conventional ensemble experiments because of the different sizes and shapes that are invariably present in the samples. These measurements allow us to study energy relaxation and propagation in nanomaterials, and how nanoparticles interact mechanically with their environment.
Superheterodyne techniques in laser ultrasonics.
Authors: Murray Todd W. , Bramhavar Suraj , Sampathkumar Ashwin , Ekinci Kamil L. , Pouet Bruno
Published: October 2009

Laser-based ultrasonics is a powerful tool for the mechanical characterization of thin films and nanostructures. In this paper, superheterodyne approaches to single-point and full-field detection of laser generated ultrasonic signals will be discussed. In these techniques, an amplitude modulated laser source is used to excite a narrow-bandwidth signal. The detection laser, incorporated into an interferometric detection scheme, is also amplitude or phase modulated at frequency that is offset from the generation laser modulation frequency by a fixed amount, serving as the local oscillator for superheterodyne detection. Introduction of the local oscillator allows for the optical down-conversion of the high-frequency intensity modulation associated with sample motion to a low and fixed intermediate frequency given by the difference between excitation and detection laser modulation frequencies. The primary benefit of using this approach is that the upper frequency bound is not dictated by the speed of the detection photodiode and electronic circuitry or, in the case of full-field detection, the frame rate of the CCD. Results are presented demonstrating single-point superheterodyne detection of gigahertz frequency bulk and surface acoustic waves using a low-frequency photodiode and full-field superheterodyne detection of megahertz vibrations of nanostructure arrays using a low frame rate camera.
Effects of speckles in laser Doppler vibrometry.
Authors: Aranchuk Vyacheslav , Sabatier James M.
Published: October 2009

Laser Doppler vibrometry has now started to become a common technique for vibration measurements, offering significant advantages due to its non-contact nature over traditional vibration sensors. When a laser Doppler vibrometer (LDV) is used for measurements of an optically rough surface, the effect of laser speckles can influence the LDV performance and its practical applications. The Doppler signal carrying the information of the vibration of the target results from the coherent addition of the light scattered from the target, which is the speckle field, with the reference beam. As a result, the Doppler signal and the demodulated velocity signal are effected by the speckle field. Changes in the speckle field caused by target motion or a scanning laser beam can generate noise on the LDV output, referred to as speckle noise. The speckle noise is caused by the combined effect of spikes in the demodulated velocity signal and the phase fluctuations of speckles. The origins of LDV speckle noise, its effect on practical vibration measurements, and methods of speckle noise reduction are presented.
Quantitative sensing of optical properties of diffusive media by pressure contrast acousto-optic imaging.
Authors: Lai Puxiang , Roy Ronald , Murray Todd
Published: October 2009

Acousto-optic imaging is a dual-wave modality that combines ultrasound with diffuse light to achieve deep-tissue imaging of optical contrast with the spatial resolution of ultrasound. While substantial progress has been made in recent years in detecting and imaging optical inhomogeneities in highly scattering media based on the acousto-optic response, quantitative measurement of subsurface optical properties remains difficult. A technique for the local and quantitative measure of the optical properties of turbid media, referred to as pressure contrast acousto-optic imaging, is presented. In this approach, the acousto-optic signals elicited by ultrasound pulses at two different peak pressures are measured, and the ratio of the amplitudes of these two signals determined. The resulting pressure ratio, once calibrated for a given set of pressure pulses, is found to give a direct measure of the optical transport mean free path of the interaction region between the light and sound. Measurements of the transport mean free path of inclusions buried in diffuse tissue phantoms, with no a priori knowledge of the optical properties of the phantom in which the inclusion is embedded or sample dimensions, are demonstrated. [Work supported by the Center for Subsurface Sensing and Imaging Systems (NSF ERC Award No. EEC-9986821).]
Modeling the response of a laser Doppler vibrometer to photoacoustic signal from solids.
Authors: Marcus Logan , Raspet Richard , Sabatier James , Aranchuk Vyacheslav
Published: October 2009

Different techniques for photoacoustic signal detection have been developed since its inception as a spectroscopic method. Detection tools such as microphones, piezoelectric sensors, laser beam deflection systems, and more have been used to study the response of different materials to photoacoustic excitation. The authors have proposed a method of detection of the photoacoustic signal from solids using a laser Doppler vibrometer (LDV). An analytical model of the phenomena underlying the change in phase of a LDV probe beam resulting from the photoacoustic effect from a condensed sample has been constructed. The model takes into account two phenomena responsible for changing phase of the LDV probe beam. The two phenomena are the surface vibrations caused by the periodic heating of the solid sample, and the fluctuations of index of refraction in air caused by the temperature variations and acoustic waves. Experimental verification of the model is discussed.
Mechanical model of bone conduction.
Authors: Chhan David , Thompson Charles
Published: October 2009

A mechanical model of the human auditory system will be presented. Of particular interest is bone conduction as a mean for energy transfer. A model is developed based on the lumped parametric model of the human ear proposed by Feng and Gang. Stapes displacement is examined for both air conduction and bone conduction (BC) stimulations. Results indicate that with the adjustment of the skull parameters, the model produced similar responses observed by various studies and experiments on BC.
Echolocation of objects by using the frequency modulated sound.
Authors: Matsuo Ikuo
Published: October 2009

Using the echolocation, bats can capture moving objects in real three dimensional space. Bats emit the frequency modulation sound and can identify objects with an accuracy of less than a millimeter. To determine delay times of multiple objects requires estimating the sequence of delay separations by extracting temporal changes in the interference pattern of the echoes. The models have been previously proposed to determine delay times of multiple objects by using the frequency modulation sound. In order to extract the temporal changes, Gaussian chirplets with a carrier frequency compatible with emission sweep rates were used, and each delay time was estimated by using the temporal changes. It was examined that this model could estimate each delay time within the accuracy less than 1 mm in the case of measuring echoes from multiple objects with the same size. In the real environment, it is necessary to estimate the multiple objects with the same and different size. In this paper, the echoes were measured from multiple objects, and it was examined that this model could estimate each delay time of these objects.
Possible role of steady streaming flows in fish hearing.
Authors: Kotas Charlotte W. , Rogers Peter H. , Yoda Minami
Published: October 2009

Over the last five years, the authors have studied the time-independent portion, or the steady streaming, of flows near model otoliths and determined that these flows encode both the direction and frequency of incident sounds. This talk summarizes these findings and discusses whether the fish ear can detect the displacements due to these flows. Although the results for a model cod otolith indicate that information relating to the direction of the local sound field is indeed contained within the flow patterns in the vicinity of the sensory macula, the threshold for the detectability of these directional cues appears to be much higher than published thresholds for directionalization in fish. There is some evidence, however, that the observed thresholds may have been underestimated. While these studies indicate that steady streaming flows may be insufficient to explain directionalization in fish, the results suggest that steady streaming may provide a mechanism for fish to hear ultrasound. [Work supported by ONR.]
Visualizing unsteady fluid flows inside the fish ear.
Authors: Kotas Charlotte W. , Rogers Peter H. , Yoda Minami
Published: October 2009

Fish sense their acoustic environment using ears that are typically able to detect sounds of O(10–103 Hz) at 80–130 dB re 1 μPa (for the Atlantic cod Gadus morhua, for example). Each ear contains three stone-like masses (the “otoliths”) embedded in a fluid filled membrane. The sulcus, a groove on one side of the otolith, is lined with O(104) sensory hair cells which presumably hear by detecting the acoustically induced motion of the fluid and tissue relative to the otolith. The “auditory retina hypothesis” suggests that the fish ear uses the fluid flow patterns, sensed by the array of hair cells, to characterize incident sounds. Although the time-independent steady streaming flow patterns have been shown to encode the frequency and direction of the oscillation (and hence incident sounds), the hair cell cilia displacements due to such flows are probably too small to be sensible. This experimental study focuses instead on the unsteady flows near a 350% model cod otolith oscillating in an otherwise still fluid. Results are presented for an otolith oscillating at different orientations (corresponding to the excitation from sounds from different directions) at frequencies of 3–25 Hz and amplitudes of 0.1–0.5 mm. [Work supported by ONR.]
Comparison of measured head-related transfer functions using spatio-temporal frequency analysis.
Authors: Morimoto Yasuko , Nishino Takanori , Takeda Kazuya
Published: October 2009

We make a comparison of measured head-related transfer functions (HRTFs) in spatio-temporal frequency domain. An HRTF is an acoustic transfer function between a sound source and the ear canal entrance, and defined as a function on time and space. The spatio-temporal frequency characteristics can be visualized and analyzed by showing the spectrum computed by multidimensional Fourier transform on time and space. In our experiments, we investigated the basic property of the spatio-temporal frequency characteristic and the difference between all data for the HRTFs obtained by numerical analysis and actual measurements. The reverberation and HRTF individuality were also examined. From the results, the characteristics were mostly concentrated in a specific band frequency, and there were also differences among databases.
Spatial principal components analysis on head-related transfer functions and individualized customization from fewer measurements.
Authors: Xie Bo-sun
Published: October 2009

Head-related transfer function (HRTF) is an individual-dependent and continuous function of sound source position and frequency. Measurement is a common way to obtain individual HRTFs. It is difficult or even impractical to measure HRTFs with high directional resolution for individual, however. To solve the problem, spatial principal components analysis (SPCA) of HRTFs and resulting customization of individual HRTF from fewer measurements were proposed in present paper. In SPCA, HRTF is decomposed as a weighted combination of common spatial basis functions (CSBFs) which are only direction-dependent, while the weights are frequency- and individual-independent. The CSBFs were derived from the measured HRTFs of 20 subjects with high directional resolution. Based on the calculated CSBFs, for any new subject, the weight coefficients can be estimated from fewer measured HRTFs data, and subsequently the individual HRTFs with high directional resolution can be customized. SPCA were applied to HRTF magnitudes and head-related impulse responses, respectively, and the individual data were customized for six subjects. Psychoacoustic experiments were also conducted to evaluate the customization performance. Theoretical and experimental results validate the performance of proposed method. [Work supported by of National Nature Science Fund of China Grant No. 10774049.]
Effect of the fundamental frequency and vocal register on the voice pitch compensation.
Authors: Okazaki Shuntaro , Mori Koichi , Cai Chang
Published: October 2009

Fundamental frequency (F0) of our vocalization is regulated by auditory feedback. Manipulation of F0 in the auditory feedback invokes compensatory F0 response in vocalization, whose amplitude is known to depend on the task (singing or speaking; instruction to follow/ignore the heard pitch change) and the averaged F0. In order to exclude the voluntary factor and to test if the vocal register affected the response amplitude, we used a parametric modulation of F0 according to the maximal sequence [TAF, Kawahara (1992)] and recovered an impulse response with deconvolution during vowel phonation at various averaged F0 (low, at speech fundamental frequency, high) and in two vocal registers (modal and falsetto). The normalized response amplitude increased with F0, which replicates the previous finding, while the vocal register change did not affect the response. Our findings clarify some of the characteristics of tasks dependency of the pitch control.
Pitch strength, tone segregation, and frequency difference limen.
Authors: Hansen Hans , Weber Reinhard
Published: October 2009

For pure tones in narrowband noise, two percepts are considered. At a sufficiently high tone-to-noise ratio, the tone can be clearly distinguished from the noise: the tone and the noise segregate. At a low signal-to-noise (S/N) ratio, slightly above the masking threshold, only a tonal noise is perceived: the tone is fused with the narrowband noise. With respect to these phenomena, two hypotheses are tested relating pitch strength, tone segregation, and frequency difference limen. The first hypothesis is that with the aforementioned stimuli, pitch strength alone is capable to serve as a segregation cue. The second hypothesis tested is that frequency difference limen is the psychophysical correlate of this sensation. Three experiments were conducted. The first experiment was an identification experiment. Listeners had to identify a segregated tone at five center-frequencies (250–4000 Hz, octave-wise) in the presence of narrowband noise. The second experiment measured the detection threshold of the tone. The third experiment determined the frequency difference limen at various S/N ratios. The results suggest that not only pitch strength can serve as segregation cue but is tied to the frequency resolvability.
The role of spectral- and temporal-envelope room-acoustic cues in auditory selective attention.
Authors: Makin Simon , Watkins Anthony , Raimond Andrew
Published: October 2009

Listeners can attend to one of several simultaneous messages by tracking one speaker’s voice characteristics. Using differences in the location of sounds in a room, we ask how well cues arising from spatial position compete with these characteristics. Listeners decided which of two simultaneous target words belonged in an attended “context” phrase when it was played simultaneously with a different “distracter” context. Talker difference was in competition with position difference, so the response indicates which cue-type the listener was tracking. Spatial position was found to override talker difference in dichotic conditions when the talkers are similar (male). The salience of cues associated with differences in sounds, bearings decreased with distance between listener and sources. These cues are more effective binaurally. However, there appear to be other cues that increase in salience with distance between sounds. This increase is more prominent in diotic conditions, indicating that these cues are largely monaural. Distances between spectra calculated using a gammatone filterbank (with ERB-spaced CFs) of the room’s impulse responses at different locations were computed, and comparison with listeners’ responses suggested some slight monaural loudness cues, but also monaural “timbre” cues arising from the temporal- and spectral-envelope differences in the speech from different locations.
The influence of different earphones on measurement values of simultaneous masking threshold.
Authors: Shen Juncong , Xie Zhiwen
Published: October 2009

In many psychoacoustic experiments, earphones or headphones are used to replay sound signals. In this paper, the influence of earphones on measurement values of simultaneous masking threshold is investigated. Three kinds of earphones (DT770 pro HD250 and ER-2) are used to measure the simultaneous masking threshold in four critical bands for ten normal-hearing subjects by using a 90% MLE procedures. These earphones had been calibrated with B&K 4153 artificial ear before used. We conclude that the characters of headphones have important impact on the measurement values of simultaneous masking threshold.
Predicting the dynamic responses of and energy flows in complex systems in the presence of model uncertainty.
Authors: Xu Hongan , Du Jingtao , Li Wen L.
Published: October 2009

As frequency increases, the dynamic behaviors of mechanical systems tend to become unpredictable due to inherent uncertainties/errors with some input variables. In statistical energy analysis the uncertainties and variances of the system responses are typically alleviated via spatial and temporal (or frequency) averaging processes which prove to be very useful for high-frequency analysis. Such processes, however, do not explicitly deal with suspicious variables and are not entirely equivalent to the statistical processing of the input variables and system responses. In this study, a robust and sophisticated method is presented for the dynamic analysis of complex systems. By combining with Monte-Carlo simulations (or other statistical methods), this model can be effectively used to address the probabilistic impact of any model variable(s) and predict the statistics of the system responses. This approach is demonstrated by examining how the vibrational responses and energy flows in a two-plate system are affected by the randomness of the model variables like thickness, Young’s modulus, coupling angle, etc. It is found that such a statistical process is particularly important and necessary in the medium frequency range where the ensemble means can still exhibit strong resonance-like behavior which may be of design interest and concerns.
Ultrasonic sound transmission through common building materials.
Authors: Farley Jayrin , Anderson Brian E.
Published: October 2009

Transmission loss measurements of building materials at audible frequencies are commonly made using various techniques such as plane wave tubes. These measurements provide vital information for control of noise isolation in architectural acoustics. To our knowledge, however, not much has been done to explore airborne ultrasonic sound transmission through common building materials. This paper will present various measurements of the ultrasonic transmission loss for various building materials over a frequency range of 20–200 kHz. The materials include fir plywood, particle board, medium density fiberboard, styrofoam, galvanized steel, and acrylic and polycarbonate plastics. This presentation will also discuss the challenges involved in making such measurements.
Vibro-acoustic analysis of an arbitrarily shaped vibrating structure.
Authors: Natarajan Logesh , Zhang Xue-feng , Wu Sean , Li Wen L.
Published: October 2009

Understanding the interrelationships between sound and vibrations of a structure is a crucial step toward developing the most cost-effective noise abatement strategy. In this paper, such interrelationships are established using Helmholtz equation least squares based nearfield acoustic holography. Specifically, the radiated acoustic pressure is linked to the normal surface velocity through a transfer function based on the spherical wave functions and spherical harmonics. The forced vibro-acoustic components (F-VACS) of a structure are identified by projecting the transfer function onto a set of mutually orthogonal basis functions. Finally, the radiated acoustic power is calculated, and contributions from individual F-VAC are indicated by the eigenvalues of the matrix that correlates the acoustic power to the normal surface velocity. The dominant F-VAC responsible for sound radiation is then linked to the dominant natural modes of the structure, which enables one to employ the most cost-effective measures to abate resultant sound by suppressing the identified natural modes. Such an approach to vibro-acoustic control is illustrated by a baffled square plate subject to a point force excitation under free-free boundary conditions. The effectiveness of this meth-odology on reducing sound radiation is demonstrated through numerical simulations. Similar methodology can also be used to abate structural vibrations.
Spatial mapping of modal damping in vibrating plates.
Authors: Öztürk Hande , McDaniel J. Gregory
Published: October 2009

Effective design and placement of damping treatments for complex structures benefit greatly from a knowledge of where the vibrational energy is being dissipated. Previously, the authors presented a method for spatially mapping contributions to the modal loss factor of a viscously damped structure [McDaniel et al., J. Acoust. Soc. Am. 125, 2603 (2009)]. The method is based on an inverse approach that uses experimental data to construct a damping matrix as a summation over elemental dashpots that connect measurement points to each other and to ground. This is followed by an assumption that ignores coupling in the modally transformed damping matrix, resulting in an expression for the modal loss factor as a weighted sum of elemental dashpots. In the present work, the method is applied to a vibrating plate with spatially distributed damping. An experiment is numerically simulated in which vibrational responses are measured at a small number of points. From these measurements, contributions to the modal loss factor are computed and used to construct a spatial map of damping effectiveness. Issues such as measurement error and modal coupling are used to further understand the method’s potential. [Work supported by ONR under Grant No. N000140810531.]
Synthetic and computational vocal fold modeling: Advances and issues.
Authors: Thomson Scott L.
Published: October 2009

The use of computational and synthetic models to simulate vocal fold vibration is discussed. First, issues pertaining to computational modeling are addressed. The results of simulations using compressible and incompressible flow models coupled with identical finite element vocal fold models are compared. It is demonstrated that because incompressible flow models lack acoustic coupling, non-physical vocal fold motion may be predicted. Also discussed is the common use of contact segments to restrict medial vocal fold motion in order to prevent complete fluid mesh collapse and subsequent solver failure. The sensitivity of vocal fold vibration and intraglottal flow response to contact segment medial placement is quantified. Two advances in synthetic modeling are then presented. Using high-speed imaging, it is shown that models based on realistic vocal fold geometry (e.g., from MRI data) produce more life-like motion than models with similar sizes and material properties but more idealized geometries. Fabrication methods for modeling the thin vocal fold epithelial layer and the flexible superficial lamina propria layer are described, and corresponding improvements to vocal fold motion are demonstrated. [Work supported by NIH.]
Experimental study of fluid-structure interaction which mimics phonation.
Authors: Krane Michael , Cates Zachary , Lani Shane
Published: October 2009

This presentation will detail some measurements of a fluid-structure interaction in a physical model of the human vocal folds. The goal of the study is to empirically determine the partition of incident airstream energy into vocal fold kinetic and potential energy, acoustic field energy, and dissipation in the glottal jet and the vocal tract resonator. The vocal system model is life-scale, and the working fluid is air. The model is made of acrylic and aluminum, with a compliant coating on the model vocal fold to simulate the mucosal layer. Airflow through the model is provided by a compressed air supply. Experiments are performed in an anechoic chamber. Measurements presented include subglottal pressure, optical characterization of model vocal fold wall motion, and sound pressure outside the “mouth” of the model. The measurements are then used as empirical input for a theoretical model of the energy flow. Trends showing the relationship between the various mechanisms of energy transfer are presented, and the implications for vocal efficiency are discussed.
The suction force on the vocal folds as an energy source for vibration and as an acoustic source.
Authors: McGowan Richard S. , Howe Michael S.
Published: October 2009

It has been shown that single-degree-of-freedom vibration of sprung shutters in a duct with a source of constant pressure is enabled when there is a change in separation point position on the shutters [M. S. Howe and R. S. McGowan, Fluid Dyn. Res. in press]. In this scenario, the flow is supposed to separate on the upstream side of the shutters as they open and on the downstream side as they close. Energy is inputted from the flow into the shutters as the shutters close because of a suction force necessary to turn a potential flow around the edge of each shutter. This suction force is also called the Coanda force in the aerodynamics literature. This time variable suction force is a dipole source of sound that is distinct from drag force source that has already been discussed [M. S. Howe and R. S. McGowan, J. Fluid Mech. 592, 367–392 (2007)]. With these theoretical considerations, an equation analogous to Fant’s equation for the glottal jet can be derived to explore glottal jet kinematics and the effect of the time-varying glottal end correction on the jet just prior to closure. [Work supported by DC-009229 to UCLA under subcontract].
Convective water transport within the human larynx during phonation.
Authors: Mongeau Luc , Wang Shuangdong , Terzibachi Karine
Published: October 2009

Proper hydration is known to be important in human phonation. Vocal fold tissue includes a significant amount of water. Sustained inhalation of partly dry air may result in convective water mass transport ultimately contributing to changes in tissue mechanical behavior, voice fatigue, and possibly trauma. In this study, numerical models were used to estimate the net amount of water mass transported from the vocal folds during various types of phonation. The commercially available code FLUENT was used for the mass transport analysis. Experiments were performed in a simple water channel to validate the approach. The convective transport coefficient for one type of hydrogel material was measured and used to approximately characterize that of real tissue. Efforts were made to estimate mass transport from numerical analysis and a number of ad hoc assumptions relative to respiratory patterns and ambient air humidity. The possible consequences of convective dehydration for voice production will be discussed. [Work supported by NIH.]
Parametric excitation of the acoustic eigenmodes of the vocal tract by motion of the vocal folds: Non-aeroacoustic mechanisms of phonation.
Authors: Ramsay Gordon
Published: October 2009

Studies of voice production have focused on aeroacoustic mechanisms of phonation, describing how energy in the background flow is converted into sources of sound. This paper describes a non-aeroacoustic mechanism that may be important in explaining how sound is generated by vocal fold vibration. According to dynamical systems theory, temporal variations in the parameters of a system may result in parametric excitation of the system. Under appropriate conditions, modulation of the parameters of the acoustic wave operator governing sound propagation in the vocal tract by changes in glottal geometry should be sufficient to induce parametric excitation of the vocal tract eigenmodes, creating sources of sound additional to those predicted by classical aeroacoustics. Rapid changes in the shape of the glottis during phonation are already known to create modulations of the formants within each glottal cycle, but the role of these modulations in exciting the formants has not been established. To test this hypothesis, we use a time-domain finite-volume simulation of acoustic wave propagation in a time-varying vocal tract to compare aeroacoustic and parametric excitation mechanisms. Results show that parametric excitation terms that transfer energy between formants, mainly at the instant of glottal closure, contribute significantly to the overall glottal source.