bluuebunny/crossref_metadata_2025 huggingface dataset:
A comparison of vowel formant frequencies in the babbling of infants exposed to Canadian English and Canadian French
Authors: Mattock Karen , Rvachew Susan , Polka Linda , Turner Sara
Published: October 2013

It is well established that normally developing infants typically enter the canonical babbling stage of production between 6 and 8 months of age. However, whether the linguistic environment affects babbling, either in terms of the phonetic inventory of vowels produced by infants [Oller & Eiler (1982)] or the acoustics of vowel formants [Boysson-Bardies et al. (1989)] is controversial. The spontaneous speech of 42 Canadian English- and Canadian French-learning infants aged 8 to 11, 12 to 15 and 16 to 18 months of age was recorded and digitized to yield a total of 1253 vowels that were spectrally analyzed and statistically compared for differences in first and second formant frequencies. Language-specific influences on vowel acoustics were hypothesized. Preliminary results reveal changes in formant frequencies as a function of age and language background. There is evidence of decreases over age in the F1 values of French but not English infants vowels, and decreases over age in the F2 values of English but not French infants vowels. The notion of an age-related shift in infants attention to language-specific acoustic features and the implications of this for early vocal development as well as for the production of Canadian English and Canadian French vowels will be discussed.
Automatic speech recognition
Authors: Espy-Wilson Carol
Published: October 2013

Great strides have been made in the development of automatic speech recognition (ASR) technology over the past thirty years. Most of this effort has been centered around the extension and improvement of Hidden Markov Model (HMM) approaches to ASR. Current commercially-available and industry systems based on HMMs can perform well for certain situational tasks that restrict variability such as phone dialing or limited voice commands. However, the holy grail of ASR systems is performance comparable to humans—in other words, the ability to automatically transcribe unrestricted conversational speech spoken by an infinite number of speakers under varying acoustic environments. This goal is far from being reached. Key to the success of ASR is effective modeling of variability in the speech signal. This tutorial will review the basics of ASR and the various ways in which our current knowledge of speech production, speech perception and prosody can be exploited to improve robustness at every level of the system.
Survey of conditions in New Zealand primary school classrooms and research on mechanisms influencing speech perception for children
Authors: Dodd George
Published: October 2013

A survey of 122 classrooms in New Zealand supports the need for low reverberation time and low background noise if classrooms are to be satisfactory. The RT of ‘‘poor’’ and ‘‘good’’ classrooms was found to be 0.6 s and 0.4 s respectively. Six ‘‘poor’’ classrooms were modified to reduce their RT to 0.4 s which changed them to ‘‘good’’ as judged by the users. The need for this low RT may result from children having a small integration time. A novel technique of reversed-segmented speech has verified that this is significantly smaller for children compared with adults. Activity noise in classrooms exhibits the cafe effect—a rising noise level as children compete to be heard—and we suggest this is caused by the Lombard effect. Values of the Lombard effect that we measured in a cohort of primary school children predict classroom levels similar to those observed. Present theory does not predict that reducing the RT from 0.6 to 0.4 s should significantly influence the cafe effect. Further work is planned to refine the theory and to identify if there are mechanisms not accounted for.
The prediction of speech intelligibility in classrooms using computer models
Authors: Dance Stephen , Dentoni Roger
Published: October 2013

Two classrooms were measured and modeled using the industry standard CATT model and the Web model CISM. Sound levels, reverberation times and speech intelligibility were predicted in these rooms using data for 7 octave bands. It was found that overall sound levels could be predicted to within 2 dB by both models. However, overall reverberation time was found to be accurately predicted by CATT 14% prediction error, but not by CISM, 41% prediction error. This compared to a 30% prediction error using classical theory. As for STI: CATT predicted within 11%, CISM to within 3% and Sabine to within 28% of the measured value. It should be noted that CISM took approximately 15 seconds to calculate, while CATT took 15 minutes. CISM is freely available on-line at www.whyverne.co.uk/acoustics/Pages/cism/cism.html
Electrophysiological responses to vibratory stimulation in the brainstem of the tadpole
Authors: Simmons Andrea M. , Two Aimee , Horowitz Seth S.
Published: October 2013

Maturation of saccular responses to vibratory stimuli in 3 axes was measured in the Rana catesbeiana tadpole across metamorphic development. The animal was suspended in a water-filled circular aluminum dish attached to a shaker table system consisting of 5 vibration exciters producing sinusoidal, translational movements in the x, y, and z planes. Multi-unit responses were recorded from the medulla with tungsten or platinum-iridium microelectrodes. Recording sites were electrolytically marked to verify electrode placement. Data were collected from 16 animals in late larval stages, before onset of metamorphic climax. Most recording sites were sensitive to vibrations in the z (vertical) direction, indicating a saccular origin of the response. Vibration frequencies of 40 Hz or below produced the strongest activity, with thresholds below a displacement of 10 nm. Secondary sensitivity was sometimes observed to either x (body-longitudinal) or y (body-lateral) directions of movement. Although some sites produced strong phase-locked activity to the stimulation, others showed more diverse temporal patterns of response. Active recording sites were found in the medial vestibular nucleus, lateral vestibular nucleus, reticular gray, and dorsal superior olivary nucleus. These data suggest that tadpole saccule is functional early in larval development, with sensitivity similar to that observed in adult bullfrogs.
The role of ocean observatories in monitoring for potential effects of man-made sound on the marine environment
Authors: Bradley David L. , D’Spain Gerald L. , Miller James H. , Frisk George V.
Published: October 2013

An important question is whether or not man-made sounds have an adverse long-term impact on the ocean environment. Clear evidence exists that an impact has occurred on some individual animals in a few cases. However, according to the 2003 National Academy of Sciences report, the degree of impact on any marine mammal population or on ocean ecosystems as a whole is unknown. An essential component of an approach to addressing this question is an ocean noise/marine ecosystem monitoring system. The monitoring regions should be global in extent and include biologically sensitive areas. The effort should be sustained so that long-term trends in ocean noise levels can be evaluated. An important aspect of the data collection effort is the type and quality of ancillary information. Ancillary data on the marine ecosystems allows determination of any impacts and data on the sources of marine noise and marine environmental properties which are required to develop metrics for evaluating and predicting the characteristics of the noise field. The ocean observatory system presently being contemplated could play an important role in establishing an ocean noise monitoring capability. [Work supported through the National Ocean Partnership Program, with sponsorship from ONR, NOAA, NSF, and USGS.]
Numerical simulation of ultrasound thermotherapy of brain with a scanned focus transducer
Authors: Behnia Sohrab , Ghalichi Farzan , Jafari Amin , Bonabi Ashkan
Published: October 2013

Brain tumors are one of the most difficult ones to treat. The margin between destruction of the tumor and damage to the surrounding tissue is narrow in the brain. Ultrasound could be an effective treatment because of its ability to propagate deep in tissue and induce temperature rise at the focus while leaving the surrounding tissue intact. This study investigates whether using a fix-focus transducer could destroy brain tumor cells, in a cost effective manner which reduces the treatment time significantly. In this work an appropriate fix-focus transducer was designed considering effective parameters and limitations which are dominant in this case. Then a real 2-D brain model was constructed from a MR image. A piece of the skull bone has been removed to allow ultrasound to propagate into the brain. The resultant pressure field and the temperature rise were calculated by Rayleigh integral and bio-heat equation on the model. The obtained results were promising indicating that toxic temperatures could be obtained in short treatment times. This could be of great advantage especially in treating primary brain tumors.
An allpass filter design method with application to piano string synthesis
Authors: Abel Jonathan S. , Smith Julius O. , Bensa Julien
Published: October 2013

A nonparametric allpass filter design method for matching a desired group delay as a function of frequency is presented. The technique is useful in physical modeling synthesis of musical instruments exhibiting dispersive wave propagation in which different frequency bands travel at different speeds. While current group delay filter design methods suffer from numerical difficulties except at low filter orders, the technique presented here is numerically robust, producing an allpass filter in cascaded biquad form, and with the filter poles following a smooth loop within the unit circle. The technique was inspired by the observation that a pole-zero pair arranged in allpass form has 2π total group delay when integrated around the unit circle, regardless of the pole location. To match a given group delay characteristic, the method divides the frequency axis into sections containing 2π total group delay, and assigns a pole-zero allpass pair to each. In this way, the method incorporates an order selection technique, and by adding a pure delay to the desired group delay, allows the trading of increased filter order for improved fit to the frequency-dependent group delay. Results are presented for modeling the group delay of a stiff piano string under several computational constraints.
Recent advances in modeling the propagation noise in high-rise cities
Authors: Li Kai Ming
Published: October 2013

In the past few decades, we have witnessed a rapid growth in mechanized transport and transportation systems. We live in a transport-dominated society which has led to a marked improvement in dispersal of land use and to the increased opportunity for the separate development of residential, commercial, and industrial areas. In dense and high-rise cities, various modes of land transportation are the primary source of noise. The problem of transportation noise is not confined by political or social frontiers. It affects the rich who may live in a quiet residential area but who must make full use of transport to maintain their affluent existence, as well as the less fortunate who must live close to a highway, a major road, or an elevated railway line. A systematic development of the capability for accurate predictions of the propagation of land transportation noise in dense high-rise cities is highly desirable. This paper summarizes the current models for predicting sound fields in urban environments and gives an overview of the recent advances of various numerical models to predict the sound field in urban environments. [Work supported by the Research Grants Council of the Hong Kong SAR Government and the Hong Kong Polytechnic University.]
Infrasound associated with the 2004 Sumatra megathrust earthquake and tsunami
Authors: Garces Milton , Caron Pierre , Hetzer Claus
Published: October 2013

Multiple infrasound arrays in the Pacific and Indian Oceans that are part of the International Monitoring System (IMS) observed three distinct waveform signatures associated with the December 26, 2004 Sumatra earthquake and tsunami. Infrasound station in Palau, Diego Garcia, Madagascar, and Kenya observed (1) seismic arrivals (P, S and surface) from the earthquake, (2) T-phases, propagated along SOFAR channel in the ocean, and coupled back to the ground, and (3) infrasonic arrivals associated with either the tsunami generation mechanism or the motion of the ground above sea level. All signals were recorded by the pressure sensors in the arrays. The seismic and T-phase recordings are due to the sensitivity of the MB2000 microbarometers to ground vibration, whereas the infrasound arrivals correspond to dispersed acoustic waves propagated through atmospheric waveguides. It appears that the arrival of the tsunami, as well as oceanic infragravity waves following the tsunami, were not observed by the infrasound stations. We show the prominent features of the arrivals, present source location estimates, discuss the absence of a signal associated with the tsunami arrival, and consider the potential for using infrasound as a discriminant for tsunami genesis.
Numerical acoustic wave propagation in the atmosphere
Authors: Ceranna Lars , Le Pichon Alexis
Published: October 2013

A method is presented which simulates the acoustic wave-field in the atmosphere using a Chebyshev pseudo spectral approach. The aero-acoustic equation of motion is solved in spherical coordinates. The computational time is significantly reduced by applying a rotationally symmetric approximation. Since the complete wave-field is calculated for the two-dimensional model the solution provides pictures of the pressure propagation from the source to the receiver. These images make it possible to study two effects in detail: How the sound and wind profiles affect the synthetic barograms for a fixed source, and in which way the source in space and time is reflected in the synthetic recordings for a stationary elastic model. Examples for both applications are shown where measured data are compared with synthetics. The recording at the German IMS station I26DE of the September 21, 2001, chemical explosion in Toulouse is considered as a benchmark for synthetic barograms calculated for two-dimensional profiles based on NRL-G2S and MSISE/HWM. In the second example the estimation of the source functions of super-sonic moving bodies is demonstrated. The synthetic waveforms are compared with the signals of two bolides recorded at the French IMS station I24FR at Tahiti from the December 1, 2003.
Contribution of infrasound monitoring for atmospheric investigations
Authors: Le Pichon Alexis , Drob Doug
Published: October 2013

The French NDC currently receives data from a number of IMS-type infrasound stations. Continuous automatic processing of the data is being performed in the [0.02–4] Hz frequency band in order to detect and characterize coherent infrasonic waves. Known and quasi permanent infrasonic sources are needed to evaluate and improve upper-wind models. Microbaroms are detected throughout the year on a global scale. Their monitoring reveals clear periodic trends in the detected bearings, providing further confirmation that long-range propagation strongly depends on the atmospheric conditions, primarily on the seasonal variability of the zonal winds. Infrasounds generated by active volcanoes also offer a unique opportunity for atmospheric studies. Recent observations in Vanuatu (New-Hebrides Islands) covering one full year show a maximal peak-to-peak azimuth deviation of ∼15. Infrasound observations are used as input of an inversion procedure to evaluate more precisely the vertical structure of the wind above the stratosphere in a range of altitude unaccessible to ground based or satellite measurements. With the increasing number of IMS stations being deployed, continuing systematic investigations into infrasonic signals from volcanoes will certainly help to advance the development of operational infrasound monitoring, and significant contributions to the understanding of atmospheric propagation could be expected.
Parabolic equation (PE) model approximations and implications for infrasound
Authors: Norris David E.
Published: October 2013

The continuous-wave parabolic equation (PE) model is widely used in the prediction of atmospheric propagation. In this study, the effects of several PE approximations are evaluated in the context of long-range infrasonic propagation. Specifically, the focus is on quantifying: phase errors resulting from different split-step Fourier (SSF) implementations, solution stability with respect to step size, and prediction sensitivity to the choice of reference sound speed. The tradeoff between improved performance gain and increased computational loading will also be considered. The study will include comparison of PE waveform predictions with measurements from infrasonic events. These comparisons are of interest in assessing the PE modeling performance, applicability, and limitations. Waveform predictions are made by integrating the continuous-wave PE model into a Fourier-synthesis Time-domain PE (TDPE).
Exploring the role of spectral integration in the perception of vowel sounds
Authors: Diehl Randy L.
Published: October 2013

Building on the important work of Chistovich and Lublinskaya [Hearing Res. 1, 185–195 (1979)], Syrdal [Speech Commun. 4, 121–135 (1985)] proposed that vowel category boundaries tend to occur in quantal regions corresponding to a 3.5 Bark bandwidth of spectral integration. This proposal was shown to be consistent with acoustic distributions of certain American English vowels. Some initial perceptual results [K. A. Hoemeke and R. L. Diehl, J. Acoust. Soc. Am. 96, 661–674 (1994)] also tended to support the role of a 3.5 Bark integrator in determining major perceptual boundaries among vowel categories. However, other evidence, reviewed here, raises doubts about the generality of Syrdal’s proposal. The negative evidence includes both within- and cross-language variation in the location of vowel category boundaries assumed to be governed by the 3.5 Bark integrator and the absence of elevated discriminability in putative quantal regions corresponding to the spectral limit of integration. [Work supported by NIDCD.]
Spectral integration in the processing of dynamic place cues for stops
Authors: Fox Robert Allen , Smith Marc
Published: October 2013

Chistovich and her colleagues have proposed the spectral ‘‘center-of-gravity’’ (COG) hypothesis suggesting that for static signals (such as steady-state vowels) spectral integration of two or more formant peaks may occur over a range of 3.5 Bark. More recently, studies have examined dynamic COG effects by modifying the amplitude of formants in time in order to create diphthong percepts. This presentation will review data demonstrating the COG effect in the processing of dynamic cues to place of articulation in stops in both voiced [da]-[ga] and voiceless [ta]-[ka] series. By changing only the amplitudes over time of a pair of sinewaves (in [da]-[ga]) or a pair of narrow band noise signals (in [ta]-[ka]) a ‘‘virtual F3 glide’’ can be created which can serve to signal the alveolar-velar place distinction. If these signals are played to listeners without being inserted into a base token, they are heard simply as frequency glides and not as two separate tones. Listener identification and discrimination responses to CV tokens with virtual and real F3 frequency transitions show similar overall patterns, but virtual transitions are less salient place cues than real transitions. An auditory model incorporating the dynamic COG effect will be described.
Training for learning Mandarin tones: A comparison of production and perceptual training
Authors: Wang Xinchun
Published: October 2013

Mandarin Chinese lexical tones pose difficulties for non-native speakers whose first languages contrast or do not contrast lexical tones. In this study, both tone language and non-tone language speaking learners of Mandarin Chinese were trained for three weeks to identify the four Mandarin lexical tones. One group took the production training with both visual and audio feedback using Kay Sona Speech II software. The target tones produced by native Mandarin speakers were played back through a pair of headphones and the pitch contours of the target tones were displayed on the computer screen on the top window to be compared with the trainees productions which appear in real time in the bottom window. Another group of participants took the perceptual training only with four-way forced choice identification tasks with immediate feedback. The same training tokens were used in both training modes. Pretest and post test data in perception and production were collected from both groups and were compared for effectiveness of training procedures.
Production quality of /r/ and /l/ liquids among Cantonese and Mandarin ESL learners
Authors: Derrick Donald
Published: October 2013

Perceptual interference theories suggest L2 language learners produce phonemes based on their native language phonology (Iverson et al., 2004, Cognition). This present study investigated the impact of differing native language segmental inventories on the acquisition of the English r/l contrast. Northern Mandarin dialects exhibit coda /r/ similar to the English bunched /r/, while Cantonese exhibits no r-like liquids (Gick et al., 2003, under review). The Mandarin segmental inventory provides more of a basis for acquiring the English r/l contrast than the Cantonese inventory. It is therefore predicted that Mandarin speakers will acquire the r/l contrast with a lower level of experience with English than the Cantonese speakers. One Cantonese and two Mandarin ESL learners produced r/l sounds in minimally contrastive English words in simple and complex onset, coda, and intervocalic positions. The data were analyzed in two ways. Four native English listeners were asked to judge for each word whether the target consonant was /r/ or /l/. Also, ultrasound tongue images were analyzed for component /r/ and /l/ gestures. Results provided partial support for the hypothesis. Implications for theories of second language acquisition will be discussed.
Children’s abilities to distinguish novel languages
Authors: Bond Z. S. , Stockmal Verna
Published: October 2013

When adults hear spoken samples of a language which they do not know, they can often identify it and discriminate between languages even when produced by the same talkers. Children have much less experience making metalinguistic judgments. How do children respond to languages which they do not know? We have conducted three experiments examining the abilities of 4-year old and 8-year old children to discriminate between spoken samples of different languages produced by bilingual talkers. We constructed listening tests from 5-second phrases excerpted from fluent reading provided by the talkers. In the three experiments, we progressively simplified the response mode employed by the children as well as the cognitive load of the task. Even in the simplest version, only a third of the 4-year-olds could do the task while the 8-year old children performed above chance in all three experiments. The younger children tended to respond different more than same, as if their criterion for same was identify.
Sparseness- and continuity-constrained seismic imaging
Authors: Herrmann Felix J.
Published: October 2013

Non-linear solution strategies to the least-squares seismic inverse-scattering problem with sparseness and continuity constraints are proposed. Our approach is designed to (i) deal with substantial amounts of additive noise (SNR < 0 dB); (ii) use the sparseness and locality (both in position and angle) of directional basis functions (such as curvelets and contourlets) on the model: the reflectivity; and (iii) exploit the near invariance of these basis functions under the normal operator, i.e., the scattering-followed-by-imaging operator. Signal-to-noise ratio and the continuity along the imaged reflectors are significantly enhanced by formulating the solution of the seismic inverse problem in terms of an optimization problem. During the optimization, sparseness on the basis and continuity along the reflectors are imposed by jointly minimizing the l1- and anisotropic diffusion/total-variation norms on the coefficients and reflectivity, respectively. [Joint work with Peyman P. Moghaddam was carried out as part of the SINBAD project, with financial support secured through ITF (the Industry Technology Facilitator) from the following organizations: BG Group, BP, ExxonMobil, and SHELL. Additional funding came from the NSERC Discovery Grants 22R81254.]
Theory and experiments for surface-wave focused acoustic arrivals: A deterministic view
Authors: Deane Grant , Preisig James
Published: October 2013

Statistical descriptions of surface wave scattering are now highly developed, and have proven very effective in relating the first and second order statistics of surface-reflected acoustic arrivals to surface conditions. Notwithstanding this success, the deterministic features of surface-scattered arrivals are of considerable importance. The limits of performance of underwater communications systems in very shallow water, for example, are determined by the frequency and properties of extreme surface focusing events. The analysis of data from the Wavefronts I, II, and V series of experiments has led to an understanding of the wave properties controlling the focusing events, as well as their impact on acoustic channel estimators. Data from the wavefronts experiments (SIO pier, 7 m deep, 40 m range) and the SPACE02 experiment (Martha’s Vineyard, 15 m depth, 250–1000 m range) will be presented and discussed. [Work supported by ONR.]
Subjective evaluation of speech and noise in learning environments in the realm of classroom acoustics: Results from laboratory and field experiments
Authors: Meis Markus , Nocke Christian , Hofmann Simone , Becker Bernhard
Published: October 2013

The impact of different acoustical conditions in learning environments on noise annoyance and the evaluation of speech quality were tested in a series of three experiments. In Experiment 1 (n=79) the auralization of seven classrooms with reverberation times from 0.55 to 3.21 s [average between 250 Hz to 2 kHz] served to develop a Semantic Differential, evaluating a simulated teacher’s voice. Four factors were found: acoustical comfort, roughness, sharpness, and loudness. In Experiment 2, the effects of two classroom renovations were examined from a holistic perspective. The rooms were treated acoustically with acoustic ceilings (RT=0.5 s [250 Hz–2 kHz]) and muffling floor materials as well as non-acoustically with a new lighting system and color design. The results indicate that pupils (n=61) in renovated classrooms judged the simulated voice more positively, were less annoyed from the noise in classrooms, and were more motivated to participate in the lessons. In Experiment 3 the sound environments from six different lecture rooms (RT=0.8 to 1.39 s [250 Hz–2 kHz]) in two Universities of Oldenburg were evaluated by 321 students during the lectures. Evidence found supports the assumption that acoustical comfort in rooms is dependent on frequency for rooms with higher reverberation times.
Acoustic and electromagnetic noise from lighting in classrooms
Authors: Laszlo Charles A. , Lashin Jonathan , Hodgson Murray R.
Published: October 2013

Following complaints by hard-of-hearing students using assistive-listening devices, and their teachers, the hum-like noise generated by fluorescent lighting was investigated in classrooms and the school library in a typical school. This hum is caused by vibrations in the core of the magnetic ballasts. Measurements were made in several rooms without students present. Noise levels increased between 7 and 15 dB when fixtures using magnetic ballasts were switched on. Spectral analysis showed the presence of 30, 60, 120, and 240 Hz components. In rooms where electronic ballasts were installed, there was no increase in noise level when the lights were switched on. Since hearing aids and assistive-listening devices worn by students may also be influenced by magnetic fields, these were also surveyed in these classrooms. The magnetic fields generated by the lights were not significant, but near some wiring and electrical panels the interference was strong. In rooms with electronic ballasts some infrared assistive-listening devices picked up strong high-frequency hum. It is recommended that the effect of lighting fixtures and the electrical-distribution system be taken into account in the acoustical and communication design of classrooms.
Posterior probability distributions for Biot parameters from experimental data
Authors: Xu Buye , Neilsen Traci , Isakson Marcia
Published: October 2013

Reflectivity measurements can be used in inversion techniques to obtain estimates of the physical characteristics of seabed sediments. In addition, computation of posterior probability distributions (PPDs) [S. E. Dosso, J. Acoust. Soc. Am. 111, 129–142 (2002)] provide an uncertainty of each parameter estimate obtained by a simulated annealing inversion. In this work, PPDs are calculated for experimental reflection loss data to evaluate the sensitivities associated with the parameters in the Biot-Stoll poro-elastic model for sediments. The data comes from a lab tank experiment in which reflection loss from a sandy sediment was measured as a function of grazing angle for frequencies between 75 kHz and 150 kHz. The sampling for the PPDs is based on the least-squares error between simulated reflection coefficient data and values modeled with the reflection module of OASES. [H. Schmidt, ‘‘OASES Version 2.1 User Guide and Reference Manual,’’ Department of Ocean Engineering, Massachusetts Institute of Technology, 1997.] The PPDs resulting from the lab data are compared with those obtained for simulated data, and the effects of experimental error on the results are explored.
Measurement of the bulk density gradient in the transition layer of a sand/water interface using a diver deployed X-Ray Attenuation Measurement System (XRAM)
Authors: Hay Todd , Isakson Marcia
Published: October 2013

The reflection coefficient is an important parameter for modeling acoustic applications in littoral environments. However, a density gradient in the transition layer of the interface can change the value of the reflection coefficient by 15 dB for high frequencies. Therefore, an accurate measurement of the bulk density gradient is crucial to the interpretation of reflection coefficient data. Previously, bulk density gradients have been determined by coring which disrupts grain microstructure or by electrical methods which do not measure the density directly. For this study, a novel means of directly determining the density gradient in situ using x-ray attenuation was developed. The system is small, lightweight, and diver deployed allowing a greater flexibility in density measurements. Calibration measurements of materials with varying densities as well as measurements of the transition layer of a sand/water interface will be presented. [Work supported by ONR, Ocean Acoustics.]
Is Lighthill’s acoustic analogy still relevant?
Authors: Richarz Werner
Published: October 2013

More than fifty years after Lighthill’s seminal paper, the acoustic analogy appears to be out of favor, even though the theory has been able to cope with all aspects of jet noise. This review examines the principal features of Lighthill’s acoustic analogy through the lens of the self-and shear noise theory (one of several possible formulations), introduced by Proudman and extended by Ribner and others. One to infer a great deal about the sound field of a jet with a minimum of information about the details of the flow. For example, the well-known U8 scaling law is readily extended to predict the variation of the far-field power spectra of jet noise. The validity has been demonstrated by applying the prediction algorithm to measured jet noise data. Correlations of the source terms and the far-field sound have been measured and shown to exhibit closure. Subtle features such as two-point correlations of far-field sound pressures are accurately described. Recently, Ribner has proposed a means by which the elusive refraction due to flow and temperature gradients can be dealt with in a consistent manner. Predictions based thereon agree quite well with measurement, even for small angle from the jet axis.
Infrasound radiation of cyclones
Authors: Naugolnykh Konstantin A.
Published: October 2013

Tropical cyclones produce strong perturbations of atmosphere and the ocean surface accompanied by acoustical radiation. Infrasonic signals in the 0.1−0.5 frequency band can be observed at distances of thousands of miles from the cyclone. The effect of infrasound radiation is connected apparently to the interaction of the counter-propagating sea-surface waves that produces a sound radiation of the doubled frequency of the surface wave oscillation. This radiation has narrow-angle vertical directivity pattern. The essential refraction of radiated infrasound in the atmosphere perturbed by the cyclone leads to trapping of the infrasound by the horizontal atmospheric wave-guide providing its long distance propagation.
Relationship between perceived politeness and spectral characteristics of voice
Authors: Ito Mika
Published: October 2013

This study investigates the role of voice quality in perceiving politeness under conditions of varying relative social status among Japanese male speakers. The work focuses on four important methodological issues: experimental control of sociolinguistic aspects, eliciting natural spontaneous speech, obtaining recording quality suitable for voice quality analysis, and assessment of glottal characteristics through the use of non-invasive direct measurements of the speech spectrum. To obtain natural, unscripted utterances, the speech data were collected with a Map Task. This methodology allowed us to study the effect of manipulating relative social status among participants in the same community. We then computed the relative amplitudes of harmonics and formant peaks in spectra obtained from the Map Task recordings. Finally, an experiment was conducted to observe the alignment between acoustic measures and the perceived politeness of the voice samples. The results suggest that listeners’ perceptions of politeness are determined by spectral characteristics of speakers, in particular, spectral tilts obtained by computing the difference in amplitude between the first harmonic and the third formant.
Converting sound speed uncertainty to an effective correlated noise term in array processing
Authors: Sarkar Jit , Cornuelle Bruce , Roux Philippe , Hodgkiss W. S. , Kuperman W. A. , Stevenson Mark
Published: October 2013

The sensitivity of the received acoustic field at an array from a specific source to perturbations of the sound speed field about a mean value can be computed using a Born approximation formulation involving forward model calculations. When this sensitivity map is appropriately combined with a covariance of the uncertainty of the sound speed perturbations, one obtains the resultant perturbation to the cross spectral density matrix (CSDM) of the acoustic field. This additional term to the mean CSDM can be thought of as a noise term resulting from the uncertainty in the sound speed field. Computations indicate that this additional term is a form of correlated noise that suggests the possibility of mitigating environmental uncertainty with a robust array processing procedure.
Improvement of time reversal communications in underwater acoustic channels using adaptive equalizers
Authors: Song Heechun , Hodgkiss William S. , Kuperman William A. , Roux Philippe , Akal Tuncay , Stevenson Mark
Published: October 2013

The spatial and temporal focusing properties of time reversal methods can be exploited for undersea acoustic communications. Spatial focusing mitigates channel fading and produces a high signal-to-noise ratio at the intended receivers along with a low probability of interception elsewhere. While the temporal focusing (compression) reduces significantly intersymbol interference (ISI), there always is some residual ISI depending upon the number of transmitters and the complexity of the channel. Moreover, a slight change in the environment over the two-way propagation interval introduces additional ISI. Using shallow water experimental data, we demonstrate that the performance of multiple-input/multiple-output time reversal communications can be improved significantly by cascading the received time series with adaptive equalizers to remove the residual ISI.
Comparison of speech intelligibility scores for direct listening and headphone playback
Authors: Bradley John S. , Sato Hiroshi , Gover Bradford N. , York Natalie
Published: October 2013

Speech recognition test scores from direct listening and headphone playback were compared to validate the use of headphone playback for investigating the effects of varied room acoustics conditions. Varied acoustical conditions for direct listening, that were representative of classrooms, were achieved using simulated sound fields in an anechoic room with an 8-channel electro-acoustic simulation system. Eight conditions consisting of the combinations of 2 reverberation times and 4 signal-to-noise ratios were used. By recording these conditions with an acoustical mannequin, headphone playback of the same conditions could be achieved and the corresponding speech recognition scores compared. Two different approaches for correcting for the microphone and headphone responses were compared. Subjects also responded to a short questionnaire to describe the audible differences between direct playback and headphone listening. Because spatial characteristics were frequently found to differ between the two listening modes, further comparisons were carried out using sound fields with systematic differences in the locations of the speech and noise sources. Although there were always some audible differences between the two playback modes, it was possible to obtain the same speech recognition scores using headphone playback as with direct listening. [Work supported by CLLRnet.]
Cavitation effects of therapeutic ultrasound
Authors: Bader Kenneth , Gipson Karen
Published: October 2013

In order to model possible effects of cavitation on bone structure, the formation of cavitation along an acoustically reflective PVC surface was studied. The bubbles were generated by a commerical therapeutic transducer (1 MHz), for both water and agar gel mediums. Bubble formation and activity were monitored using light scattering techniques: a HeNe laser was directed through the medium, and the transmitted light was detected using an optical power meter. The data show a decline in cavitation activity further from the surface and offer suggestive evidence of a boundary layer. Temporal saturation is also evident in both mediums, though an anomalous increase in transmitted light for the agar medium suggests the possibility of pressure variations due to microstreaming. Analysis of the microstreaming pattern was subsequently performed at lower frequencies in order to allow visualization with a standard laboratory microscope.
Phase preservation in musical signals
Authors: Vijayakumar V. , Eswaran C.
Published: October 2013

The intensity variations of the harmonics of musical instruments in the frequency domain can be interpreted to store phase information. The motivation for this arises by considering the similarity of the timbre of in- struments to that obtained through a diffraction model proposed here. The intensity modifications of an input spectrum of discrete frequencies of unit intensity into the known spectra of different musical instruments have been found to match that of known instruments. According to diffraction theory, the modifying envelope encodes phase information. By considering the similarity, it is proposed that musical instrument timbre store phase information. It is suggested that timbre itself could have diffraction origins. Specific examples of musical instruments are considered to illustrate this intepretation.
Practical system for recording spatially lifelike 5.1 surround sound and 3D fully periphonic reproduction
Authors: Miller Robert E. (Robin)
Published: October 2013

In acoustic spaces that are played as extensions of musical instruments, tonality is a major contributor to the experience of reality. Tonality is described as a process of integration in our consciousness over the reverberation time of the room of many sonic arrivals in three dimensions, each directionally coded in a learned response by the listeners unique head-related transfer function (HRTF). Preserving this complex 3D directionality is key to lifelike reproduction of a recording. Conventional techniques such as stereo or 5.1-channel surround sound position the listener at the apex of a triangle or the center of a circle, not the center of the sphere of lifelike hearing. A periphonic reproduction system for music and movie entertainment, Virtual Reality, and Training Simulation termed PerAmbio 3D/2D (Pat. pending) is described in theory and subjective tests that capture the 3D sound field with a microphone array and transform the periphonic signals into ordinary 6-channel media for either decoderless 2D replay on 5.1 systems, or lossless 3D replay with decoder and five additional speakers. PerAmbio 3D/2D is described as a practical approach to preserving the spatial perception of reality, where the listening room and speakers disappear, leaving the acoustical impression of the original venue.
Application of cochlear analysis techniques to percussion in electro-acoustic music
Authors: Mills John
Published: October 2013

This presentation is focused upon the audio analysis involved in the creation of a ‘‘pseudo-score’’ for electro-acoustic music. This research was undertaken because the lack of an objective visual representation prevents music theorists from being able to easily discuss electro-acoustic music in written form. The ‘‘holy grail’’ of automatic computer music analysis has most often been the translation of a continuous pressure variation into traditional Western musical notation. Since electro-acoustic music is rarely able to be transcribed into this type of notation, the automatic analysis of electro-acoustic music confounds many previous algorithms. A top-down approach is suggested in order to extract acoustic and musical information from recordings of electro-acoustic music. Because humans are the best known system for translating a continuous pressure variation into useful acoustic information, a cochlear model, Patterson’s Auditory Image Model (AIM), is used as a front end. The audio property of self-similarity of percussion has been chosen for initial study. This self-similarity property requires first that the audio property of percussion is quantified. The nuances of using AIM to determine percussion will be discussed. Models of self-similarity of percussion for varying time-scales will then be discussed.
Hearing conservation practices in eight noisy industries
Authors: Daniell William E. , Swan Susan S. , Camp Janice , Cohen Martin , McDaniel Mary M. , Stebbins John , Leo Robert
Published: October 2013

This study evaluated noise exposures and hearing conservation practices at 76 companies in eight industries with high rates of workers’ compensation claims for hearing loss. Nearly all companies had exposures that required a hearing conservation program, and more than half had exposures that required consideration of noise controls. The use of noise measurements and consideration of controls was low in all industries. The completeness of hearing conservation programs was strongly associated with the extent of exposure in an industry, although practices varied widely within industries. Most companies had substantial deficiencies. More than one-third did not conduct annual training, and training had shortcomings at many others. One-third had not conducted audiometry. Hearing protection was commonly underused. Reported use was highest at companies with relatively complete programs, and in industries where exposure was most prevalent and least intermittent. Many employees had difficulty estimating how often, and presumably when, their exposure was excessive. There is a need for new strategies to promote and maintain hearing conservation efforts in noisy industries. The industries with greatest margin for improvement are not the noisiest industries but those where exposure is moderate or intermittent. [Work supported by the National Institute for Occupational Safety and Health.]
Intermediate scale measurement system for underwater acoustic measurements
Authors: Niemiec Jan M. , Shang Paul C. , Schreppler Stephan
Published: October 2013

The Intermediate Scale Measurement System (ISMS) provides high quality acoustic measurements on large-scale submarine models and other underwater structures in a controlled environment. Development and implementation of advanced marine technology designs require a thorough understanding of structural acoustic response mechanisms. The only practical and cost effective approach to developing this understanding is through the use of a combination of numerical models and large-scale physical models. The ISMS provides an affordable, unique capability of making precision acoustic measurements on models large enough to contain the structural detail and the instrumentation required to understand structural acoustic mechanisms and to confirm and guide the use of numerical models. This is a key element for prediction of full-scale performance and integration of advanced submarine technologies into operational systems.
Complete regularization of boundary integral equations in wave field diffraction problems on curved surfaces
Authors: Maximov German A. , Lesonen Dmitry N.
Published: October 2013

The method of regularization of exact integral Fredgolms equations of the second kind for field or its normal derivative on the scattering surface was suggested in the previous work. It allows to obtain the stable solutions, including ones for the resonant domains, when the direct numerical solution of exact initial integral equations results to unstable solutions. Mathematically the regularization concludes in the splitting of exact integral Fredgolms equations on the equivalent system of two equations, one of them possesses the restricted by geometrically illuminated area integral operator, and other one corresponds by form to an initial one, but with diffracted source. The solution of the first equation is considered as regularized one, which coincides with exact solution in the short wavelength limit. From the physical point of view the regularization of initial integral equations concludes in their replacement on the restricted analogs, where the contributions of geometrically shadowed areas are eliminated. In the given work the regularization of the rested after splitting integral equation is represented and it is shown that the process of such regularization is auto-similar one, so that it is possible to carry out the complete regularization of the problem.