bluuebunny/crossref_metadata_2025 huggingface dataset:
Numerical simulation of wave propagation in air including the effects of molecular relaxation and relative humidity
Authors: Wochner Mark S. , Atchley Anthony A. , Sparrow Victor W.
Published: September 2013

The research reported is directed at developing a computational model for assessing the importance of nonlinear propagation in the near field of jet engines. In order to attain accurate results, more complete models of acoustic wave propagation are required. The goal of the current research is to develop a two-dimensional time domain solution to the Navier–Stokes equations that includes the effects of classical absorption, relative humidity, and molecular relaxation of diatomic nitrogen and oxygen. Using fluid dynamics equations from Pierce [Acoustics: An Introduction to Its Physical Principals and Applications (ASA, New York, 1989)], a system of equations is created and solved using finite difference schemes. Benchmark cases will be discussed to show that the code is capable of reproducing the physical phenomena associated with atmospheric absorption and the relative importance of the various attenuation mechanisms will be discussed. [Work supported by ONR.]
Terrain effects on acoustic pulse propagation
Authors: Albert Donald G.
Published: September 2013

Outdoor sound propagation was measured at a variety of locations to determine terrain and environmental effects on acoustic pulses. Small explosive charges were detonated at a height of 1.5 m above the ground, and the resultant acoustic pulses were digitally recorded using pressure sensors located 10 to 100 m from the source. The experiments were conducted in an open area over concrete, grass, or snow; through a forest or thick tropical vegetation; and along a building-lined street in an artificial village. The measurements reveal that waveform changes occur at the shortest measurement ranges and increase as the propagation distance increases. These changes include amplitude attenuation, pulse width, and waveform shape and are caused by the differing ground conditions. The highest peak amplitudes at 100 m were recorded over concrete, and the lowest over snow-covered ground, with peak pressure decay rates of 24- and 32-dB/decade distance in these two situations. In addition, multiple scattering and reflected arrivals were visible in the tropical, forest, and urban areas. [Work funded by U.S. Army.]
3D shear wave generation in soft tissues using the time reversal kaleidoscopes
Authors: Palacio Delphine , Bercoff Jeremy , Montaldo Gabriel , Tanter Mickael , Fink Mathias , Sarvazyan Armen , Sutin Alexander
Published: September 2013

The time reversal kaleidoscope provides elegant possibilities for both temporal and spatial concentration of acoustic energy in a wide frequency band. Using such ultrasound focused beams, it is possible to generate mechanical sources radiating low frequency shear waves inside tissues. Shear waves are of great interest to investigate tissue viscoelastic properties. In most techniques relying on this concept, generation and imaging of shear waves are realized with a single ultrasonic probe, limiting the capabilities concerning the generation of the shear source. Here we propose a system able to generate and image shear waves in a full 3D volume with any kind of polarization. The focused beam is generated by the time reversal kaleidoscope. By combining the concepts of time reversal mirrors and chaotic reverberating cavities, the time reversal kaleidoscope is able to focus ultrasound beams in a large 3D volume with only some tens of transducers and presents equivalent performances than conventional 2D matrices made of thousands of transducers. The kaleidoscope is triggered by an ultrafast imaging system able to image the resulting shear waves. In vitro results in tissue mimicking phantoms are presented. Chaotic cavities of different geometries are tested and compared. [Work supported in part by NIH grant.]
Time reversal for source detection in urban environment
Authors: Liu Lanbo , Albert Donald G.
Published: September 2013

This paper applies the time reversal method to acoustic source detection in an outdoor urban environment. Experimental measurements were conducted in a full-scale artificial village to determine the effect of buildings on sound propagation outdoors. Explosive charges were detonated to produce acoustic pulses that were digitally recorded by sensors scattered throughout the village. We use the two-dimensional finite difference time domain (FDTD) method to compute synthetic time traces for acoustic propagation within the artificial village. The FDTD model predicted arrival times and amplitude levels that are in fair agreement with the measured data at most microphone measurement locations. Using the simulated time traces and the measured data from only nine stations and back propagating them into the model, the sound energy refocuses in the vicinity of the true source location. Our time reversal experiment confirms that the phase information is more critical than sound pressure levels and that using information acquired only at non-line-of-sight (NLOS) locations is sufficient to obtain accurate source locations. The results demonstrate that time reversal can potentially be used for fast source location in a complex urban terrain and noisy acoustic background, with without requiring LOS sensors. [Work funded by U.S. Army.]
Revisiting the Stokes relations in a time-reversal cavity: Suppression of intraplate echoes induced by a titanium plate
Authors: Aubry Jean-Francois , Vignon Francois , Tanter Michael , Montaldo Gabriel , Fink Mathias
Published: September 2013

When focusing through plates or tubes the presence of multiple interfaces induces reflected wavefronts that follow the main wavefront. Adaptive focusing techniques can be used to cancel the echoes. For that purpose, two linear arrays of transducers have been placed on each side of a titanium plate. Three propagation operators have been acquired: transmission from one array to the other, and two reflection operators acquired by each array. In this work, two adaptative focusing methods have been used to cancel the echoes: first, they have been suppressed with a time-reversal mirror, using the two arrays’ cavity surrounding the plate. Second, the echoes have been canceled by using the inverse filter technique, inverting the transmission operator. Thus, the inverse filter achieves echo cancellation by using only the transmitted fields, whereas time reversal also requires the reflected fields. It is shown how transmission and reflection operators are related by the Stokes relations in a matrix formalism. These relations clearly exhibit how the inverse filter takes advantage of the reflections in the medium. An iterative mathematical resolution of these equations yields a new way to invert the transmission operator.
Time reversal imaging of noise sources inside a reverberant room
Authors: Ribay Guillemette , Roux Cédric , de Rosny Julien , Fink Mathias
Published: September 2013

In a reverberant room, the multiple reflected echoes make imaging of acoustical random sources difficult. In this talk, we give an original solution based on Time Reversal Principles. Basically, in a first step, the acoustic field due to a noise source is recorded by a set of microphones. In a second step, all the recorded signals are time-reversed and re-emitted by loudspeakers that now replace the microphones. We observe a strong enhancement of the mean intensity around the initial source position. In a first part, we highlight the formal link between time-reversal of pulsed and noise sources in reverberant media. Especially we deduce that the signal to noise ratio depends only on the number of pairs of microphone/loud speaker for noise sources. Numerical simulations confirm these predictions. In a second part, we present experimental results performed in a 5*3*3=m and reverberant room. The intensity map of noise acoustic sources with a working bandpass of [100–3000] Hz has been performed. The same experiment has been carried out with two coherent or incoherent sources. Moreover, the frequency dependence of the resolution obtained with this technique is studied. Finally, we focus on the SNR with respect to the bandpass and central frequency.
Localization of multiple-band noises in the median plane
Authors: Ng Gerald , Colburn H. Steven
Published: September 2013

Six subjects reported the perceived location of two sets of noise stimuli presented through speakers in the median-sagittal plane. Two sets of stimuli were generated by passing flat (1 to 16 kHz) Gaussian noise through multiple, equal-amplitude bandpass filters. The control stimulus included all frequencies between 1 and 16 kHz. The first set contained two to six equally-spaced, 1/3-octave-wide noise bands. The second set contained five equally spaced noise bands that varied in common bandwidth. Loudspeakers in the medial-sagittal plane were located at six frontal locations (−30, −15, 0, 15, 30, 45, with 0 directly in front) and two rear locations (120, 180). The experiments were conducted in a sound-treated room with the speakers concealed from view. Stimuli were 200 ms in duration and presented from one speaker per trial. Subjects used a pen to mark perceived stimulus locations on preprinted coordinate diagrams. Despite noticeable intersubject differences, most subjects localized stimuli with five or six 1/3-octave-wide bands as well as control stimuli. Many subjects showed steady decreases in accuracy as the bandwidths of five bands were reduced. HRTFs were recorded for each listener, and several model algorithms are being evaluated. [Work supported by NIDCD Grants R01 DC00100 and P30 DC04663.]
Itakura distance measure used to study speech intelligibility in a room using white noise
Authors: Sommerhoff Jorge , Cardenas Jorge , Poblete Victor , Barros Jose Luis
Published: September 2013

The recognition process of isolated words use distance measures to determine if the word corresponds to one of its vocabulary. In this investigation Itakura distance measure was used to compare the segments of white noise of two signals with different relationships of direct and reverberant energy densities. Interesting data is obtained from the distance measure in the function of the position of the microphone in the room in which a white noise source is continuously working. These results could be useful to develop a new methodology to measure the word intelligibility in a room. There were carried out some comparative measurements with Rasti and intelligibility test. [Work supported by DID–UACh.]
A shot-noise phase-opponency model for monaural detection of pure tones in noise at low frequencies
Authors: Gai Yan , Carney Laurel H.
Published: September 2013

Phase-locked responses of low-frequency auditory-nerve (AN) fibers contain sufficient information for detection of a tone in noise. The phase-opponency (PO) model [Carney et al., Acustica 88, 334–347 (2002)] uses relative phase across fibers with different characteristic frequencies (CFs). The model’s discharge rate is reduced when a tone is added to noise due to changes in the coincidence of the rate functions across AN CFs. In the current study, a shot-noise model for coincidence detection was used to implement the PO model. AN discharge times were simulated using an AN model with a discharge generator; therefore, internal noise was naturally included in the AN input fibers. Model results were compared to human data for detection of a 500-Hz tone in reproducible noises, which provided external noise. The aim was to test the hypothesis that the shot-noise PO model explains human performance in terms of thresholds, hit- and false-alarm rates, and to understand the performance for different reproducible noises. The ratio of the internal to external noise in the shot-noise PO model depended on combining responses of several identical but independent cells. [Work supported by NIDCD R01-01641.]
Effect of masker onset asynchrony on overshoot in simultaneous masking
Authors: Miskiewicz Andrzej , Buus Soren , Florentine Mary
Published: September 2013

This study examines how overshoot is influenced by asynchrony between the onsets of an on-frequency center-band noise masker (CB) and a flanking noise band (fringe). Thresholds were measured for 2-ms tones at 5 kHz gated on 2 ms after the onset of the CB. Measurements were made with only the CB (4590–5464 Hz), and with either a low fringe (1900–4590 Hz) or a high fringe (5500–11000 Hz) added to the CB. The fringe came on between 500 ms before and 100 ms after the CB onset. Because previous studies demonstrated that overshoot is produced only by masker components outside the auditory filter centered at the signal frequency, overshoot is taken as the increase in threshold caused by adding the fringe. Results show that considerable overshoot, 7–11 dB, is produced by a high fringe gated on within 10 ms before or after CB onset; overshoot is maximum when the fringe and CB come on simultaneously. Maximum overshoot with a low fringe is less than 4 dB. The finding that a high fringe increases threshold even when it comes on shortly after the signals end suggests that overshoot is governed primarily by central mechanisms. [Work supported by NIH/NIDCD Grant R01DC00187.]
Sinusoidal spectral modulation masking period patterns
Authors: Saoji Aniket , Eddins David A.
Published: September 2013

Knowledge of the internal auditory representation of spectral envelope features is critical to the understanding of auditory perception by listeners with normal and impaired hearing. Previous investigators have used forward and simultaneous masking to derive masking patterns that reveal the influence of lateral suppression and other factors on the internal representation of various spectral envelopes (e.g., narrowband noise and steady-state vowels). The present study followed a general approach, in which the internal representation of spectral shape was estimated on the basis of spectral masking patterns obtained with sinusoidal spectral modulation. Simultaneous- and forward-masked thresholds were measured for probe signals as a function of spectral modulation frequency (cycles/octave), phase, and depth (peak-valley contrast in dB) superimposed on a noise carrier (400–6400 Hz). For relatively low modulation frequencies (<1 cycle/octave), masking patterns closely mimicked features of the external spectrum. For very high modulation frequencies (>2 cycles/octave), masking patterns revealed reduced spectral contrast, consistent with the limited frequency selectivity of the auditory system. For intermediate modulation frequencies (1–2 cycles/octave), considerable spectral sharpening was evident. The three-dimensional space defined by spectral modulation frequency, depth, and internal contrast will be discussed in terms of predicting the internal representation of arbitrary complex spectral envelopes.
Perceptual learning of talker-specific vowel space
Authors: Queen Jennifer S. , Nygaard Lynne C.
Published: September 2013

Previous research suggests that as listeners become familiar with a speaker’s vocal style, they are better able to understand that speaker. This study investigated one possible mechanism by which this talker familiarity benefit arises. Listeners’ vowel spaces were measured using a perceptual discrimination test both before and after they were trained to identify a group of speakers by name. Listeners identified either the same speakers whose vowels they discriminated or a different group of speakers. Differences in the learnability and the intelligibility of the two speaking groups were observed. The speaker group that was harder to identify also had vowels that were harder to discriminate. Changes in the listeners’ vowel spaces were determined by examining multidimensional scaling solutions of their responses during the discrimination tests. All listeners became better at discriminating vowels. However, only listeners who heard different speakers during identification training and vowel discrimination exhibited a shift in their vowel spaces after training. This suggests that encountering new voices in an unrelated, nonlinguistic task acts to alter the perceptual context and may affect the structure of linguistic representation. Together, these results suggest a link between linguistic and nonlinguistic information in representations for spoken language.
Significance of analysis window size in maximum flow declination rate
Authors: Carroll Linda M.
Published: September 2013

Most acoustic stability measures and aerodynamic measures have recommended data analysis methods to ensure accurate comparison across research studies. Although standard aerodynamic analysis methods exist for subglottal pressure and mean transglottal flow, such standards do not exist for maximum flow declination rate (MFDR). As such, it becomes difficult to compare results across studies with the wide range of analysis windows. Because MFDR is a strong indicator of laryngeal function and increasingly is being reported in aerodynamic studies, it is necessary to determine whether a significant difference exists between analysis windows in data management. This study finds significant differences in MFDR with comparison of four different data extraction methods on the same data set. The contrasting data extractions compare differences between method A (MFDR from entire 1000-ms segment, excluding onset/offset), method B (MFDR from middle 100 ms with center at midportion of entire segment), method C (MFDR from middle 100 ms with center at midportion of maximum MFDR value from entire segment), and method D (MFDR from 20 consecutive cycles with center at midportion of maximum MFDR value from entire segment) for a sustained 7-syllable /pa/ repetition at two fundamental frequencies.
A comparison of harmonic production in trained and untrained singers
Authors: Hildebrand Jonathan H , Caso Hilary J.
Published: September 2013

This study was designed to investigate the differences in the tone qualities of trained and untrained singers of both genders by measuring the ratio of energy found in the fundamental frequency to that found in the harmonics of the two groups. Forty trained and untrained male and female subjects (ten in each group) sang the vowels [a e i o u] in the words ‘‘me cake father obey too.’’ Each subject sang through the list of words in its entirety one time. They were also asked to produce each word at a constant pitch of their choosing. The intensity (dB) was then measured at the vowel midpoint in the intact vowel, and then again with the fundamental filtered out. These two measurements allowed for a comparison to be made by subtracting the results. This process produced results showing that the fundamental frequency was responsible for the majority of the trained singers’, vocal productions, where harmonics were responsible for the majority of the untrained singers’, vocal productions. The data also showed that these results were more prominent for the production of the high vowels in both genders, and for women overall.
Lexical frequency and voice assimilation in complex words in Dutch
Authors: Ernestus Mirjam , Lahey Mybeth , Verhees Femke , Baayen Harald
Published: September 2013

Words with higher token frequencies tend to have more reduced acoustic realizations than lower frequency words (e.g., Hay, 2000; Bybee, 2001; Jurafsky et al., 2001). This study documents frequency effects for regressive voice assimilation (obstruents are voiced before voiced plosives) in Dutch morphologically complex words in the subcorpus of read-aloud novels in the corpus of spoken Dutch (Oostdijk et al., 2002). As expected, the initial obstruent of the cluster tends to be absent more often as lexical frequency increases. More importantly, as frequency increases, the duration of vocal-fold vibration in the cluster decreases, and the duration of the bursts in the cluster increases, after partialing out cluster duration. This suggests that there is less voicing for higher-frequency words. In fact, phonetic transcriptions show regressive voice assimilation for only half of the words and progressive voice assimilation for one third. Interestingly, the progressive voice assimilation observed for higher-frequency complex words renders these complex words more similar to monomorphemic words: Dutch monomorphemic words typically contain voiceless obstruent clusters (Zonneveld, 1983). Such high-frequency complex words may therefore be less easily parsed into their constituent morphemes (cf. Hay, 2000), favoring whole word lexical access (Bertram et al., 2000).
Viscoelastic properties of the false vocal fold
Authors: Chan Roger W.
Published: September 2013

The biomechanical properties of vocal fold tissues have been the focus of many previous studies, as vocal fold viscoelasticity critically dictates the acoustics and biomechanics of phonation. However, not much is known about the viscoelastic response of the ventricular fold or false vocal fold. It has been shown both clinically and in computer simulations that the false vocal fold may contribute significantly to the aerodynamics and sound generation processes of human voice production, with or without flow-induced oscillation of the false fold. To better understand the potential role of the false fold in phonation, this paper reports some preliminary measurements on the linear and nonlinear viscoelastic behavior of false vocal fold tissues. Linear viscoelastic shear properties of human false fold tissue samples were measured by a high-frequency controlled-strain rheometer as a function of frequency, and passive uniaxial tensile stress-strain response of the tissue samples was measured by a muscle lever system as a function of strain and loading rate. Elastic moduli (Young’s modulus and shear modulus) of the false fold tissues were calculated from the measured data. [Work supported by NIH.]
Continuous speech recognition using dynamic synapse neural network
Authors: Dibazar Alireza A. , Namarvar Hassan H. , Berger Theodore W.
Published: September 2013

The modified architecture of the dynamic synapse neural network (DSNN) is used to model windowed short time speech signal. The quasi-linearization algorithm is applied to train the network. The parameters of the trained network, which are representatives of the signal, are fed into the GMM/HMM based classifier. The performance of the modified architecture with GMM/HMM based classifier is demonstrated by recognition of continuous speech from unprocessed, noisy raw waveforms spoken by multiple speakers. Our results indicate that the features obtained from DSNN are robust in the presence of additive white Gaussian noise with respect to state-of-the-art Mel frequency features. [Work supported in part by DARPA, NASA and ONR.]
New virtual sonar and wireless sensor system concepts
Authors: Houston B. H. , Bucaro J. A. , Romano A. J.
Published: September 2013

Recently, exciting new sensor array concepts have been proposed which, if realized, could revolutionize how we approach surface mounted acoustic sensor systems for underwater vehicles. Two such schemes are so-called ‘‘virtual sonar’’ which is formulated around Helmholtz integral processing and ‘‘wireless’’ systems which transfer sensor information through radiated RF signals. The ‘‘virtual sonar’’ concept provides an interesting framework through which to combat the dilatory effects of the structure on surface mounted sensor systems including structure-borne vibration and variations in structure-backing impedance. The ‘‘wireless’’ concept would eliminate the necessity of a complex wiring or fiber-optic external network while minimizing vehicle penetrations. Such systems, however, would require a number of advances in sensor and RF waveguide technologies. In this presentation, we will discuss those sensor and sensor-related developments which are desired or required in order to make practical such new sensor system concepts, and we will present several underwater applications from the perspective of exploiting these new sonar concepts. [Work supported by ONR.]
Compact, high power, energy efficient transmit systems for UUVs using single crystal transducers
Authors: Robinson Harold
Published: September 2013

UUVs are currently being designed to perform a multiplitude of tasks in ocean exploration and Naval warfighting. Many of these tasks require the use of active acoustic projectors, and many may require the UUV to operate independently for hours, days, or even weeks. In order for a UUV to be as versatile as possible, its active transmit system must be versatile as well, implying that broad acoustic bandwidths are a must. However, due to size and battery life limitations, this broadband system must also be compact and energy efficient. By virtue of their extraordinary material properties, ferroelectric single crystals are the ideal transduction material for developing such broadband systems. The effect of their high coupling factor on transmit systems shall be illustrated by showing the dramatic impact on amplifier size, power factor, and acoustic response that is possible using these materials. In particular, a transducer built with these materials can be well matched to the power amplifier, i.e., 80% or more of the amplifier power reaches the transducer, over decades of frequency. Measured results from several prototype single crystal transducers shall be presented to demonstrate that the theoretical gains are actually realizable in practical devices. [Work sponsored by DARPA.]
Study on the correlation between the old city and the newly developed city regarding audible sound types and sound levels
Authors: Tokashiki Takeshi , Yamashita Yasuhiro , Takagi Naoki
Published: September 2013

Sound-level data are the most important among the appraisal data of environmental noise. However, to appraise diversified environment like that of the present times, a more detailed appraisal on environmental noise could be obtained by conducting subjective appraisal in addition to the physical noise level. In this research, we have surveyed subjective appraisal, audible sound types and sound level (LAeq) along boulevard, commercial, and residential areas in the old city and the newly developed city. The subjective appraisal by examinees shows that of the 100% of noise along boulevards, traffic sound occupies 80%; of the 60% of noise in commercial areas the traffic sound occupies 65%; and of the 40% of noise in residential areas the traffic sound occupies 50%. We have studied the correlation between the result of the same surveyed in the old city and the newly developed city. There have been fewer study cases about the correlation between sound types and subjective appraisal; therefore, in this paper we have studied this correlation.
Time-domain equations for sound propagation in or reflection from rigid porous media
Authors: Ostashev Vladimir E. , Wilson D. Keith , Collier Sandra L.
Published: September 2013

In acoustics, many absorbing materials can be considered as porous media with rigid frames. Therefore, studies of sound propagation in or reflection from rigid porous media are important in many applications. These studies are usually done in the frequency domain where equations describing sound propagation in or reflection from porous media are well established. However, there are also problems where such equations are needed in the time domain. Examples include studies of material properties by acoustic impulses and finite-difference time-domain (FDTD) simulation of sound propagation in the presence of absorbing surfaces. In this paper, using Wilson’s relaxation model for acoustical properties of porous media [D. K. Wilson, Appl. Acoust. 50, 171–188 (1997)], we derive a closed set of time-domain, integro-differential equations for the sound pressure and particle velocity in rigid porous media. In the limiting cases of low and high frequencies, these equations coincide with those known in the literature. Furthermore, in these limiting cases, using the relation model, we derive time-domain boundary conditions for sound reflection from a porous medium. This result can be used in FDTD simulation of sound propagation outdoor. [Work supported by the DoD High Performance Computing Modernization Office and ERDC-CRREL.]
Is a moving average field a proper macro scale measure?
Authors: McCoy John J.
Published: September 2013

A number of derivations of the Biot equations governing the acoustics of fluid-filled, porous solids, which are based on a more complete formulation that applies to all length scales, accept moving averages of the response fields that enter the more complete formulation as the response fields that enter the Biot equations. This raises a question: Does a moving average field incorporate only macro scale variation? A moving average field is presented as one extreme of a class of fields that is formed from sets of discrete local spatial averages. The set of local spatial averages for a moving average field is accomplished for locations that are separated by a vanishing distance. The opposite extreme of a field of local averages is formed from a set of local averages accomplished for locations that are separated by a distance equal to a linear measure of the region of the spatial average. Explicitly demonstrated is that the moving average of a field that contains both macro and micro scale variation will itself contain both macro and micro scale variation. The relative suppression of the micro scale variation compared to the macro scale variation, which obtains in one representation of the moving average field, is only apparent; the micro scale variation can be recovered by an appropriate signal processing. This is in contrast to a wavelet-defined field of local averages, an example of the other extreme, for which the suppression of the micro scale variation is absolute. The issue is significant for a derivation of a prediction model that purports to output macro scale response fields.
Generation of subharmonic and difference frequency acoustic waves in a water-saturated sandy sediment
Authors: Kim Byoung-Nam , Lee Kang Il , Yoon Suk Wang , Choi Bok Kyoung
Published: September 2013

Generation of subharmonic and difference frequency acoustic waves in a water-saturated sandy sediment was investigated. Subharmonic frequency acoustic wave was observed to be generated due to the nonlinearity of water-saturated sandy sediment when the fundamental frequency acoustic wave exceeded a certain threshold pressure amplitude. Pressure spectrum level of the subharmonic frequency acoustic wave linearly increased as the driving acoustic pressure amplitude increased. The pressure level was 10 dB higher than the background noise level. Generation of the difference frequency acoustic wave was also observed by the collinear acoustic waves with two different fundamental frequencies. The pressure level of the difference frequency acoustic wave was 5 dB higher than the background noise level. It seems very useful to evaluate the nonlinear parameter of water-saturated sandy sediment without disturbing the sediment. Such nonlinear acoustic responses of water-saturated sandy sediment can be utilized for the diagnosis of marine gassy sandy sediment.
Surface and plate mode stimulation in piezoelectric materials in the framework of inhomogeneous wave theory
Authors: Declercq Nico F. , Degrieck Joris , Leroy Oswald
Published: September 2013

Inhomogeneous waves are already a well established concept in ultrasonics. Whenever damping is present, such waves become inevitable when reflection and transmission phenomena have to be described. The concept of inhomogeneous waves has been established in the study of acoustics in liquids, isotropic solids and also anisotropic solids. It has been shown before that inhomogeneous waves are much better in stimulating surface waves and plate modes than plane waves and general bounded beams. Nevertheless the concept has not been introduced yet in the field of piezoelectric media. The current paper describes the interaction of inhomogeneous waves with piezoelectric solids of any kind of anisotropy and shows how surface and plate modes can be excited by means of such waves. [Work supported by The Flemish Institute for the Encouragement of the Scientific and Technological Research in Industry (I.W.T.).]
The time course of laryngeal coarticulation in children: First results
Authors: Koenig Laura L.
Published: September 2013

Previous work has suggested that the degree or extent of coarticulation is more extreme in young children than adults. Research in this area has focused primarily on supralaryngeal aspects of coarticulation, using spectral measures such as formant frequencies and fricative centroids. At the same time, studies of adults have found that laryngeal adjustments for voiceless consonants extend well into neighboring vowels, yielding higher values of open quotient and DC flow, and more symmetical pulse shapes, in vowels flanking voiceless as compared to voiced consonants. The current work investigates laryngeal coarticulation in normally developing, English-speaking 4- and 5-year olds. Inverse filtering of the oral airflow is used to approximate the glottal source signal in utterances containing /VpV, VhV, VbV/ sequences. The /VbV/ utterance, which does not require vocal-fold abduction, serves as a control condition to the voiceless consonants. Voice source (open quotient, speed quotient) and aerodynamic (AC and DC flow) quantities are measured over time, and compared between the children and adult females. Along with adding to our understanding of developmental changes in coarticulation, these data will contribute to the literature on differences in voice source properties between children and adults. [Work supported by NIH.]
Spectral moments versus Bark cepstrum classification of children’s voiceless stops
Authors: Polikoff James , Hammond Jenna , McNicholas Jane , Bunnell H. Timothy
Published: September 2013

Spectral moments have been shown to be effective in deriving acoustic features for classifying voiceless stop release bursts [K. Forrest, G. Weismer, P. Milenkovic, and R. N. Dougall, J. Acoust. Soc. Am. 84, 115–123 (1988)]. In this study, we compared the classification of stops /p/, /t/, and /k/ based on spectral moments with classification based on an equal number of Bark cepstrum coefficients. The speech tokens were 446 instances each of utterance-initial /p/, /t/, and /k/ sampled from utterances produced by 208 children 6 to 8 years old. Linear discriminant analysis (LDA) was used to classify the three stops based on four analysis frames from the initial 40 ms of each token. The best classification based on spectral moments used all four spectral moment features and all four time intervals and yielded 75.6% correct classification. The best classification based on Bark cepstrum yielded 83.4% correct also using four coefficients and four time frames. Differences between these results and previous classification results using spectral moments will be discussed. Implications for future research on the acoustic characteristics of children’s speech will be considered.
Exploring production-perception relationships for 4-year-old children: A study of compensation strategies to a lip-tube perturbation
Authors: Menard Lucie , Perrier Pascal , Savariaux Christophe
Published: September 2013

The relationships between production and perception for 4-year-old children were examined through a study of compensation strategies to a lip-tube perturbation. Acoustic and perceptual analyses of the rounded vowel [u] produced by 12 4-year-old French speakers were conducted under two conditions: in normal condition and with a 15-mm-diam tube inserted between the lips. Recordings of isolated vowels were made in normal condition before any perturbation (N1), immediately upon insertion of the tube (P1), for each of the next 20 trials in this perturbed condition (P2), and in normal condition after the perturbed trials (N2). Results of the acoustic analyses reveal speaker-dependent alteration of F1, F2, and/or F0 in the perturbed conditions and after the removal of the tube. For some subjects, the tube introduced very little changes; for some others, an increase of F2 was observed in P1, which was generally at least partly compensated during the P2 repetitions. Perceptual data are used to determine optimal combinations of F0, F1, and F2 (in bark) related to these patterns. The data are compared to a previous study conducted with adults [Savariaux et al., J. Acoust. Soc. Am. 106, 381–393 (1999)].
Spectral frequency modulation in vowel identification
Authors: Liu Chang , Eddins David A.
Published: September 2013

Psychophysical and physiological studies have demonstrated selectivity for spectral envelope frequency (also termed spatial frequency) in the auditory system, suggesting that auditory perception of complex sounds might be based on spectral envelope channels. The present study investigated relative contribution of different spatial frequencies to vowel identification. Twelve naturally-spoken American-English vowels were presented at 70 dB SPL. In different conditions, vowel stimuli were subjected to various degrees of low-pass and high-pass filtering in the spatial frequency domain, in effect, altering their spectra. Identification performance for the vowels with and without spatial frequency filtering was estimated for normal-hearing listeners. Results indicated that vowel identification performance was progressively degraded as spatial-frequency components were removed. Results will be interpreted in terms of spatial frequency regions most important to specific vowel categories. The specificity and universality of spatial frequency modulations in vowel identification across different vowel categories will be discussed.
Tongue–jaw kinematic correlates of /s/ spectra
Authors: Dembowski James S. , Crumb Richard K.
Published: September 2013

Frequencies of spectral peaks for fricatives are determined by the size of the resonating cavity anterior to the place of articulatory constriction in the upper vocal tract. For /s/, this cavity size may be altered through anterior–posterior (a–p) movements of the tongue blade forming the constriction, changes of jaw height, and degree of lip protrusion. With respect to intensity, modeling studies suggest that intensity of fricative spectral peaks may be related to degree of articulatory constriction. These spectral–kinematic relationships have been little studied in natural speech. This study used data from the University of Wisconsin X-Ray Microbeam Database to examine the relationship between spectral peaks and movements of the tongue and jaw in the /s/ productions of one normal speaker. Results showed no relationship between a–p tongue position and frequency of spectral peaks. However, a significant inverse correlation related peak between frequency and jaw opening. Thus, for this speaker jaw height appeared a more important determinant of spectral variability for /s/ than tongue position. Additional results showed a significant relationship between peak intensity and distance of the tongue blade from the palate. These natural speech data will be discussed with respect to models and theories of fricative production.
Correlation between angle of incidence and sliding patterns of the tongue along the palate in Korean velar stops
Authors: Brunner Jana , Fuchs Susanne , Perrier Pascal , Kim Hyeon—Zoo
Published: September 2013

In former studies, it has been hypothesized that the articulatory production of oral stops could result from the interaction between the tongue moving towards a virtual target located above the palate, and the palate. Velar stops, where the tongue slides along the palate during the occlusion phase, offer a nice experimental framework for further experimental assessments. Indeed, in the framework of the ‘‘virtual target’’ hypothesis, the sliding movement should be seen as the continuation of the movement before the occlusion, but constrained by the palate. Hence, relations should exist between the movement characteristics before contact and during the occlusion phase. To test this hypothesis three Korean speakers were recorded via EMA producing /aCV/ sequences with C=/g/, /k’/ and /kh/, V=/a/, /i/ or /u/. The angle between tongue trajectory just before the impact and palatal contour was estimated, and the amplitude of the sliding movement was measured. Preliminary results for two speakers show that these two variables correlate: The greater the angle, the larger the sliding movement. These findings are interpreted as supporting the ‘‘virtual target’’ hypothesis. This interpretation will be verified by simulations using a 2D biomechanical tongue model [Payan and Perrier, Speech Commun. 22 (1997)].
Modeling the acoustics of American English /r/ using configurable articulatory synthesis (CASY)
Authors: Lehnert-LeHouillier Heike , Iskarous Khalil , Whalen Douglas H.
Published: September 2013

The claim that articulatory variation in /r/ production exhibits systematic tradeoffs to achieve a stable acoustic signal (Guenther et al., 1999) was tested using configurable articulatory synthesis (CASY) and ultrasound data. In particular, the hypothesis was tested that multiple constrictions during /r/ production are necessary to achieve a low enough F3. Ultrasound and Optotrak data from four speakers pronouncing /r/ in different vocalic contexts were used to determine where in the vocal tract the tongue gestures are placed. This data was then modeled using CASY parameters and was used to determine how the three gestures in /r/ (labial, palatal, and pharyngeal) contribute to the F3 value observed in the speech signal simultaneously recorded with the ultrasound. This was done by varying the degree and location of the lingual constrictions and the degree of the labial constriction and determining the effect on F3. It was determined that the three gestures in /r/ contribute in differing amounts to the overall F3 lowering. Furthermore, it does not seem that all three gestures are necessary for F3 lowering. This lends support to the hypothesis that the goal in /r/ production is the simultaneous achievement of three gestures. [Work supported by NIH Grant DC-02717.]
Acoustic identification of a single transmission at 3115 km from a bottom-mounted source at Kauai
Authors: Spiesberger John L.
Published: September 2013

Sounds received in the Gulf of Alaska at 3115 km from the ATOC/NPAL source at Kauai (75-Hz, 0.027-s resolution, bottom-mounted) are compared with acoustic and oceanographic models. Unlike data collected at stationary SOSUS arrays, these data come from a towed horizontal array at 372-m depth of military origin. A plausible identification of the acoustic reception is made despite the fact that only one transmission is collected and sound interacts with the bottom near the source. The similarity between the modeled and measured impulse response here may be useful for understanding the signals between this same source and the NPAL array near southern California. The plausible identification of sound from the horizontal array here appears to point toward the feasibility of using other military platforms of opportunity besides SOSUS to study acoustic propagation and possibly map climatic changes in temperature by means of tomography.
Head waves in the Yellow Sea
Authors: Choi Jee Woong , Dahl Peter H.
Published: September 2013

Signals akin to head waves were obtained from explosive sources during the joint U.S. and China Yellow Sea experiment, conducted in August 1996. The sources were deployed at ranges from 0.7 to 37 km in waters approximately 75 m deep. Data were recorded on a 16-element vertical line array with element spacing of 4 m and the deepest element at depth 66 m. This talk will focus on measurements obtained at source ranges less than 1 km, because the amplitude of the head wave arrivals decreases rapidly with range. The arrival time and power spectra were first used to identify and distinguish ground-, water-, and head-wave arrival types. This latter category was then further studied in the context of pure head waves, noninterfering head waves, and interference head waves. The experimental data are also compared with simulated signals obtained via a Fourier synthesis of a narrow-band complex parabolic equation (PE) field, using the RAM PE code. The overall influence of compressional velocity, velocity gradient, and attenuation in the sediment, and frequency dependency of head wave arrivals are discussed. [Research supported by ONR Ocean Acoustics.]
The effect of compression and attention allocation on speech intelligibility. II
Authors: Choi Sangsook , Carrell Thomas
Published: September 2013

Previous investigations of the effects of amplitude compression on measures of speech intelligibility have shown inconsistent results. Recently, a novel paradigm was used to investigate the possibility of more consistent findings with a measure of speech perception that is not based entirely on intelligibility (Choi and Carrell, 2003). That study exploited a dual-task paradigm using a pursuit rotor online visual-motor tracking task (Dlhopolsky, 2000) along with a word repetition task. Intensity-compressed words caused reduced performance on the tracking task as compared to uncompressed words when subjects engaged in a simultaneous word repetition task. This suggested an increased cognitive load when listeners processed compressed words. A stronger result might be obtained if a single resource (linguistic) is required rather than two (linguistic and visual-motor) resources. In the present experiment a visual lexical decision task and an auditory word repetition task were used. The visual stimuli for the lexical decision task were blurred and presented in a noise background. The compressed and uncompressed words for repetition were placed in speech-shaped noise. Participants with normal hearing and vision conducted word repetition and lexical decision tasks both independently and simultaneously. The pattern of results is discussed and compared to the previous study.
Some anomalous time domain back scattering phenomena from low contrast fluid spheres and cylinders
Authors: Feuillade C. , Chu D. , Clay C. S.
Published: September 2013

Anderson’s scattering theory [J. Acoust. Soc. Am. 22, 426–431 (1950)], and the corresponding formalism for an infinite cylinder, have been used to calculate the scattered impulse responses for low contrast fluid spheres and cylinders, where the density and sound speed of the object are fractionally higher than the surrounding medium. The returns from the front and rear faces of the object are individually identifiable. In the case of a sphere, both of these features are positive spikes. In the cylindrical case, the second feature is a negative first derivative of a spike. In both instances, the waveform of the second feature is different from that expected from simple physical reasoning, i.e., the raypaths and reflection coefficients. The predictions of the calculations are investigated by using them to analyze experimental scattering data from decapod shrimp near broadside incidence. By convolving the calculated impulse response with the incident acoustic signal, comparisons with the scattering data are made. Both the sphere and cylindrical calculations appear to fit the data well. The significance of these results, and possible explanations for the anomalous scattering from the rear face, are discussed. [Work supported by ONR, University of Wisconsin Weeks Fund.]
ISO/IEC 17025 laboratory accreditation of NRC Acoustical Standards Program
Authors: Wong George S. K. , Wu Lixue , Hanes Peter , Ohm Won-Suk
Published: September 2013

Experience gained during the external accreditation of the Acoustical Standards Program at the Institute for National Measurement Standards of the National Research Council is discussed. Some highlights include the preparation of documents for calibration procedures, control documents with attention to reducing future paper work and the need to maintain documentation or paper trails to satisfy the external assessors. General recommendations will be given for laboratories that are contemplating an external audit in accordance to the requirements of ISO/IEC 17025.