bluuebunny/crossref_metadata_2025 huggingface dataset:
The analysis, interaction, and measurement of loudspeaker far-field polar patterns
Authors: Baird Justin E. , Meyer Perrin S.
Published: July 2002

This paper discusses some issues related to the measurement and representation of loudspeaker far-field polar pattern data (also known as directivity patterns). The mathematical framework of this method is based on approximating the time-harmonic far-field complex acoustic pressure field using the sum of spherically weighted acoustic point sources. One issue that is discussed in detail is a method where the far-field polar pattern is estimated by rotating a loudspeaker on a turntable and measuring the response at equally spaced intervals. It is often asserted that in order for the far-field data to be most useful, this ‘‘point of rotation’’ must correspond to an ‘‘effective acoustical center.’’ However, this location is often not known a priori, and often a single ‘‘effective acoustical center’’ does not exist or varies with frequency. A simple mathematical transform is developed to move the ‘‘point of rotation’’ of a measured far-field polar pattern to a different location, simplifying the choice of a rotation point. Experimental evidence showing the usefulness of this transform is presented from careful measurements of a model loudspeaker rotated in an anechoic chamber.
Harmonic distortion of sound produced by a directional, airborne, parametric source array
Authors: Brammer Anthony J. , Havelock David I.
Published: July 2002

A parametric source in which sound is generated by nonlinear interaction between collinear ultrasonic beams forms an attractive alternative to a broadband, end-fire array of conventional loudspeakers. The acoustic output of an amplitude-modulated, plane-circular piston ultrasonic source has been recorded in an anechoic chamber by a microphone positioned on, and off, the axis of axial symmetry. Attention has been paid in the experiments to minimize spurious signals generated by radiation pressure (from the intense ultrasound), or by distortion within the microphone, or receiver electronics. The ultrasonic source was operated at 30 kHz, and possessed a beam width of 8 deg and bandwidth of approximately 4 kHz (−3 dB). Acoustic signals were generated by pure-tone amplitude modulation of the ultrasonic drive signal at frequencies from 0.25 to 2 kHz. Parametric generation of sound was confirmed by measurements of the decay in sound pressure with axial distance from the ultrasonic source, the change in sound pressure level with the level of ultrasound, and the directionality patterns at 4 m. The generation of second harmonic distortion will be discussed as a function of modulation depth and drive frequency, within the limitations imposed by the bandwidth of the ultrasonic source.
Intelligibility improvement of cellular phone speech in a noisy environment
Authors: Saito Mutsumi , Fukudome Kimitoshi , Tsumura Takashi
Published: July 2002

In a noisy environment cellular phone users often have difficulties in hearing far-end speech because the ambient noise disturbs the user’s understanding of the conversation. To improve speech intelligibility in noise, speech enhancement is a feasible solution. In this paper the effects of two speech enhancement methods, multiband amplitude compression and formant enhancement, are reported. The multiband amplitude compression is a typical method for hearing aids that divides speech signal into some frequency bands and conducts amplitude compression independently. On the other hand, the formant enhancement is an LPC analysis-synthesis technique that provides for formant frequency shaping. The performances of these methods on the speech intelligibility were evaluated in the simulated real-world noise circumstances. Recorded noise sounds were presented from loudspeakers in a soundproof room and the speech samples were reproduced from real cellular phone handset which was fixed on the subject’s head. VCV (vowel–consonant–vowel sequence) units were used as test speech samples. The results show that multiband amplitude compression makes significant improvement in speech intelligibility and does not degrade the subjective impression of speech.
Dan Martin as JASA editor
Authors: Beyer Robert T.
Published: July 2002

Dan Martin’s interest in JASA goes back to his college days, but his major role has been in the position of patent review editor, in which role he worked faithfully for 20 years and, of course, as editor-in-chief for the past 14 years. Like Lindsay before him, he took the post just after serving as President of the Society, and presided over major changes in the journal, including a steady expansion of its size and the plunge into electronic publishing. Dan conducted these operations with skill, patience, and efficiency, and the Society’s debt to him is great.
Architectural requirements of pipe organs
Authors: Wetherill Ewart A.
Published: July 2002

Dan Martin invested a lifetime in the design and building of both pipe and electronic organs and in their spatial requirements for optimum performance in places of worship. He combined the still-evolving discipline of room acoustics with a musical instrument old enough to be mentioned in the book of Genesis. As editor-in-chief of the Journal of the Acoustical Society, he actively supported education in acoustics and broader understanding of architectural responsibility in the design of organ spaces. There could be no more appropriate tribute to his work than to continue his efforts in an era when worship space design is in constant flux and when the very need for any type of organ is often in question. This paper summarizes the fundamental requirements of successful organ installation with the hope of promoting heightened awareness and understanding by architects, builders, and the people who populate building and budget committees.
Hertzian contact Lamb wave sensors for NDE
Authors: Degertekin F. Levent , Pei Jun , Khuri-Yakub B. T.
Published: July 2002

Lamb waves have long been used for ultrasonic testing and evaluation of platelike structures with success. Emerging applications of in situ defect detection and process monitoring in high-temperature, harsh environments impose significant challenges for conventional techniques. Hertzian, dry contact transducers offer an effective and economic solution to some of these challenges. In this paper, selective excitation of the lowest-order Lamb waves using Hertzian contact transducers is analyzed using the normal mode theory and the results are compared with experiments. Using silicon crystal plates as the test case, it is shown that these transducers can be used to measure the phase velocity of Lamb waves very accurately. In addition to materials characterization, several other NDE applications are also discussed. An ultrasonic temperature sensor for rapid thermal processing of semiconductor wafers and a thin film thickness sensor implemented in an aluminum sputtering station are given as process monitoring applications in high-temperature, vacuum environments. The defect detection results are presented in the context of pipe erosion corrosion monitoring and composite plate delamination detection. The dual thickness-distance inversion and tomographic imaging capabilities of the sensors are also shown on stainless steel and aluminum plate samples.
Fluid pressure distribution due to outer hair cell excitation in a 3-D dual chamber model of cochlea
Authors: Parthasarathi Anand A , Grosh Karl , Ren Tianying , Nuttall Alfred L
Published: July 2002

In this study, basilar membrane (BM) velocity and the total fluid pressure distributions arising from exciting only the outer hair cells (OHCs) at a particular location in the cochlea are modeled. The cochlea is modeled using standard idealizations such as rectangular cross-section and linear inviscid fluid satisfying Laplace’s equation. Two fluid chambers, one each above and below the cochlear partition (CP), are used. A simplified micromechanical model consisting of the BM, OHC, stereocilia, and tectorial membrane (TM) represents the CP. The formulation is solved using a hybrid finite element method. A localized excitation of the OHCs causes fluid pressure disturbances, which propagate toward the apex and stapes (emissions). Both steady state and transient responses, and also the influence of boundary conditions at the apex, round window, and the oval window will be presented. Emission results will be compared to electrically evoked otoacoustic emissions for gerbils to determine the ability of the model to predict these experimental results, such as propagation velocities. [Work supported by NIH NIDCD RO1 DC00141, RO1 DC00078, and RO1 DC04084-01.]
Mechanisms of directional hearing in toadfish (Opsanus tau)
Authors: Fay Richard R. , Edds-Walton Peggy L.
Published: July 2002

Neurophysiological experiments on toadfish indicate the different strategies by which toadfish localize sources in azimuth and elevation. The saccules of the toadfish respond with great sensitivity to acoustic particle motion in the manner of inertial accelerometers. The directional response properties of otolithic afferents were studied in the horizontal and mid-sagittal planes using a 3-D shaker system. Most primary afferents have a cosine directionality response pattern. In the horizontal plane, an afferent’s best azimuthal direction is determined primarily by the orientation of the otolith organ in the head, and azimuth could be encoded as interaural response differences deriving from each organ’s gross directionality. The elevation of the axis of particle motion could be represented by a within-organ pattern of response magnitude over the afferent array that is determined by the patterns of hair cell orientation. In humans, source elevation can be estimated from the head-related transfer function, a monaural computation based on tonotopy. In toadfish, the saccule is not organized tonotopically, but directly with respect to the elevation of most effective particle motion. Thus, sound localization in fishes could be based on mechanisms of monaural and binaural computation substantially similar to those operating in other vertebrates. [Work supported by NIH and NIDCD.]
Developing a physical basis for acoustic perception. Part I: Introduction to endogenous microwaves, formation of critical bands
Authors: Stocklin Philip L.
Published: July 2002

The physical theory of brain-generated standing microwaves was first proposed in 1979 [P. L. Stocklin and B. F. Stocklin, T.-I.-T. J. Life Sci. 9, 29–51 (1979)] and their existence experimentally verified in the mid-1980’s [see Session BBB, A.S.A. 114th National Meeting, Fall 1987]. Generation of such waves is one effect of energy changes in neural transmembrane proteins during normal brain activity. During exposure to acoustic stimuli, the primary auditory cortex [AI] is identified as the major microwave source. Properties of the standing microwaves resulting from the anatomy and cochleotopicity of the AI result in the perception known as critical bands, as well as providing a physical basis for other perceptive phenomena. Following a synopsis of endogenous microwave properties, the physical basis for critical bands is discussed as a particularly clear example.
Gap detection: Effects of temporal location and stimulus duration
Authors: Crawley Edward J. , Pastore Richard E. , Skelly Michael
Published: July 2002

Three experiments evaluated a recent finding that gap detection thresholds vary nonmonotonically as a function of the temporal location of the gaps relative to the onset of the carrier noise burst [Brown and Nicholls (1997)]. Specifically, gaps presented in the temporal center of the noise burst required shorter durations to be detected relative gaps presented either near the onset or offset of the noise burst. This finding contrasts with a previous experiment that, although directly testing for such an effect, did not find an effect of temporal location [Forrest and Green (1987)]. The current experiment 1 replicates, and formally presents, the temporal location effect reported by Brown and Nicholls. Experiment 2 rules out bias, uncertainty, and task demands as possible contributing factors to the observed effect. Experiment 3 then demonstrates that the size of this effect varies with the overall duration the noise burst thus leading to a possible reconciliation of the findings of the previous studies. The current results will be discussed in terms of their ability to reconcile a number of apparently inconsistent findings in the gap detection literature as well as their similarity to effects observed in a simultaneous masking task.
Parametric investigation of the virtual glide
Authors: Iyer Nandini , Eaton Babette , Sridharan Ramkumar
Published: July 2002

This study examined the perceptual spectral integration effect using dynamic signals called ‘‘virtual glides’’ (Lublinskaya, 1996; Anantharaman et al., 1997). A virtual glide was generated by modulating the amplitude of two sinusoids at fixed frequencies (f1 and f2) which were centered at fc, with a frequency separation of Δf. Initially, the level of f1 was higher than the level of f2. Over the duration of the signal, the level of f1 decreased linearly while the level of f2 increased at the same rate. This produced the percept of a frequency glide; hence the name ‘‘virtual glide.’’ The subjects’ task was to match the rate of change of a real glide to that of a virtual glide using Jesteadt’s (1980) double staircase matching procedure. The fc, Δf, and duration of the stimuli remained constant within a block. The fc of the virtual glide was varied (500, 1000, 2000 Hz), as was Δf (2, 4, 5, 6, 8 ERB). Further, the stimuli were presented at three different durations (125, 250, 500 ms). The slope of the linear glide was varied adaptively to obtain the 50% point of subjective equality (PSE). We investigated the range of Δf and signal duration over which listeners could perform this task.
Just discriminable change of velocity of a simulated moving sound source
Authors: Hassett Sarah M. , Feth Lawrence L.
Published: July 2002

The Doppler effect refers to the frequency change observed for a moving sound source. The listener will observe a higher than emitted frequency in front of the moving source and a lower frequency behind it. Although the existence of the Doppler effect has been long documented, relatively little experimental work has investigated the human perceptual response to frequency and intensity changes due to moving sound sources. This experiment determined the just discrminable change of velocity of a computer simulated moving sound source. Subjects were tested at 500, 1000, and 4000 Hz for reference velocities of 1, 2, 4, and 8 m/s. Signal duration was 500 ms. A 2-Q,2-AFC adaptive procedure determined the listener’s velocity difference limen (DL). At 500 Hz, the smallest DL was 10.46 m/s at reference velocity 8 m/s. The DL increases as the reference velocity decreases. This pattern is evident at all tested source frequencies. Weber fractions were calculated for both velocity DLs and frequency deviation. The results indicate that both velocity DL and frequency deviation increase as reference decreases, signifying that Weber’s law does not hold for source velocity and frequency. [Work supported by a College of Arts and Sciences Honors Scholarship and a grant from the College of Social and Behavioral Sciences.]
Testing time, occlusion effects, and required masking for insert earphones versus supra-aural headphones
Authors: Hayes Donald
Published: July 2002

In a recent survey of audiologists [Martin et al., J. Am. Acad. Aud. 9, 95–100 (1998)] the authors reported that only 24% of respondents used insert earphones in any capacity. Surprisingly few clinicians use insert earphones even though they have several desirable qualities relative to supra-aural headphones. Insert earphones are reputed to eliminate ear canal collapse, reduce occlusion, and increase interaural attenuation. The purpose of this study was to determine the extent to which insert earphones might increase the speed and ease with which hearing tests are obtained. Audiometric assessments were obtained on 91 individuals in the course of their standard clinical investigations. ER-3A insert earphones were used to assess 46 of them and the other 45 were tested using TDH-39 supra-aural headphones. The audiometric tests of the two groups were compared on the basis of: testing time, earphone-related occlusion effects, necessity for masking the nontest ear, collapsed ear canals, and occluded or collapsed insert earphones. The insert earphones were found to be superior in every category. It is strongly recommended that ER-3A insert earphones should become the earphones of choice for audiometric assessment.
An energy finite element optimization process for reducing high-frequency vibration in structures
Authors: Borlase George A. , Vlahopoulos Nickolas
Published: July 2002

The energy finite element analysis (EFEA) offers an attractive alternative to the established statistical energy analysis (SEA) for simulating high-frequency structural vibration [N. Vlahopoulos et al., ‘‘Numerical Implementation, Validation, and Marine Applications of an Energy Finite Element Formulation,’’ accepted by the Journal of Ship Research]. One of the main benefits of utilizing EFEA in a simulation based design process is the capability to assign local damping properties on selected sections of a component. In this work, an optimization routine is integrated with an EFEA solver in order to optimize the distribution of damping over a structure. The formulation of the optimization process, the definition of the design variables, the constraints, and the objective function will be discussed. The validation and an application case will be presented. [Research supported by Michigan Seagrant and the U.S. Coast Guard.]
Psychophysical and cognitive limitations to speech perception by cochlear implant users
Authors: Svirsky Mario A. , Kaiser Adam R. , Meyer Ted A. , Shah Ashesh , Simmons Peter M.
Published: July 2002

Deaf listeners with cochlear implants (CIs) achieve significant levels of speech recognition, but their performance range remains wide. Unfortunately, our understanding of the speech perception mechanisms employed by CI users is still incomplete. In particular, we do not know the exact combination of acoustic cues that are employed by CI users to understand speech, nor do we understand how sensory information is represented and combined, and how that information is used to perform speech identification. We have attempted to address this issue by developing mathematical models (Multidimensional Phoneme Identification or MPI models) that aim to predict phoneme identification for individual cochlear implant users based on their discrimination along specified acoustic dimensions. Mathematically, the MPI model is a multidimensional extension of the Durlach–Braida model of loudness perception. The MPI model can explain most of the vowel pairs or consonant pairs that should be more frequently confused by groups of CI users. In this presentation we will discuss individual data suggesting that speech perception by CI users may be limited by two kinds of factors: psychophysical (i.e., limited jnd’s along relevant acoustic dimensions) and cognitive (related to imperfect integration of different acoustic cues). [Work supported by NIDCD (R01-DC03937), NOHR and DRF.]
Factors contributing to speech perception in children implanted before age 5
Authors: Geers Ann
Published: July 2002

This report describes results obtained from 92 8- and 9-year-old children who received a Nucleus-22 implant before age 5. Educational and rehabilitation history was obtained from questionnaires completed by parents, cochlear implant centers, and therapists. Speech perception measures included tests of phoneme discrimination (VIDSPAC), closed set word recognition (ESP, WIPI), open set word (LNT) and sentence (BKB) recognition, and visual enhancement (CHIVE). A multivariate analysis was conducted to predict results on speech perception measures from educational variables, while controlling for effects of IQ, socioeconomic status, age at onset of deafness, age at implant, and type of speech processor and map characteristics such as number of active electrodes, dynamic range, and growth of loudness. Results indicate about half of the variance in auditory speech perception is accounted for by factors related to characteristics of the implant itself. However, significant additional variance attributable to rehabilitation factors is observed. Children educated primarily in oral settings showed a significant advantage in speech perception. Amount and type of intervention following implication has a significant impact. [Work supported by NIH.]
Condition assessment of steel stringer highway bridges using experimental modal analysis
Authors: Lenett Mike , Turer Ahmet , Brown David
Published: July 2002

An experimental modal testing procedure has been developed for assessing the condition of steel stringer highway bridges using an optimized rapid impacting testing procedure. A 30 m to 90 m long two lane bridge can be instrumented and tested in a 5- to 6-h period using a multiple reference impact testing procedure. A special spatial domain multiple reference parameter estimation algorithm is used to obtain a modal model from the measured multiple reference impact data. The modal model is used to predict the static response of the bridge to various loading conditions. This predicted flexibility of the bridge is a good indication of the state of the bridge and can be use to assess the bridge. In the development phase of this procedure, the reliability of the resulting flexibility was verified by comparing measured truckload displacements against simulated truckload displacements, which were computed by virtually loading the modal flexibility matrix with a truckload. Furthermore, induced damage scenarios revealed that modal flexibility was an excellent objective, kernel index for both global and local condition assessment. The modal model is also used in the calibration of a nominal 3-D–FE model which is used in evaluating the rated load capacity of the bridge.
Multiple scattering in fish and zooplankton acoustics is the exception
Authors: Foote Kenneth G.
Published: July 2002

Reference is made to the general literature on multiple scattering. This indicates that multiple scattering is negligible if the following condition is fulfilled: ρ≪2πλ−2σ−1/2, where ρ is the numerical density of scatterers, λ is the acoustic wavelength, and σ is the maximum single-scatterer differential scattering cross section. The condition is examined for three classes of aquatic organisms: fish, euphausiids, and copepods. It is amply satisfied for all plausible organism concentrations and frequencies excepting possibly those of schooling swimbladder-bearing fish at resonance. [Partial support of the EU through RTD-Contract No. MAS3-CT95-0031 is acknowledged.]
Measurement of directional information in sound fields
Authors: Gover Bradford N. , Ryan James G. , Stinson Michael R.
Published: July 2002

The directional characteristics of sound arriving at a listening point in a room are being studied with a view to improving microphone pickup of speech in teleconference rooms. Knowledge of the directions from which the direct, reflected, and reverberant sounds arrive is expected to be useful in microphone array design. At present, there exist several techniques which attempt to measure the direction of sound arrival, based on comparisons and postprocessing of multiple microphone signals. This postprocessing can involve intensity analysis, deconvolution analysis, or cross-correlation analysis. Each of these approaches has its benefits, drawbacks, and tradeoffs, and may perform better or worse in a given situation. Studies of several of these directional measurement techniques are underway to ascertain their usefulness and validity in a variety of situations, through both simulations and real room measurements.
Legends of echoes linked through acoustics to prehistoric art
Authors: Waller Steven
Published: July 2002

A new area for acoustic research has arisen from a previously unsuspected relationship between ancient legends of echoes, and prehistoric rock art. This art includes Ice Age deep cave paintings, and Native American petroglyphs typically found high on canyon walls. This acoustic connection is important because there has been no satisfactory explanation of the motivation for the production of rock art (neither the unusual locations nor the subject matter the artists chose). Yet producing rock art clearly was a major preoccupation for early Homo sapiens sapiens over a span of tens of thousands of years. The concept of sound wave propagation and reflection is a modern paradigm, and is based on the abstraction of invisible pressure waves being diverted by boundaries between media of different densities. In ancient times, however, the causes for many natural phenomena were explained by personification or animism, including attributing echoes to be the responses of spirits. Could echoes have motivated the ancient artists? Acoustic studies at rock art sites may be starting to answer this important question.
Ultrasonic tissue cutting with silicon surgical tools
Authors: Lal Amit
Published: July 2002

Ultrasonic cutting is a well accepted way to cut tissues. However the exact nature of the cutting is complicated and not well understood. Cavitation, direct cutting, inertia stiffening, and thermal damage are just some of the effects believed to occur. Furthermore, we have been developing silicon-based ultrasonic surgical tools that hold promise for more functional surgical tools. In this paper we present results on the measurement of forces during ultrasonic cutting. Temperature sensors embedded in the tissue are used to measure any ultrasound-induced heating. We will present force and temperature data measured with actuators with different frequencies and intensities. Tradeoffs between the cutting tip sharpness and ultrasonic tip velocity effecting tissue damage will be presented in the context of Hertzian contact theory. We will use this data to formulate a phenomenological theory of ultrasonic cutting useful to design transducers for ultrasonic cutting. [Work supported by the Whitaker Foundation.]
Ultrasound-induced cell lysis and sonoporation enhanced by contrast agents
Authors: Ward Mark , Wu Junru
Published: July 2002

The enhancement of ultrasound-induced cell destruction, lysis, and sonoporation in low cell concentration suspensions (2×105/mL) by the presence of contrast agents (gas bubble to cell ratio =3D 230) was demonstrated using cervical cancer cells (HeLa S3) suspensions containing micron-size denatured albumin microspheres filled with air (Albunex=AE) or octafluoropropane (OptisonTM). The suspensions were insonificated by 2-MHz continuous or toneburst ultrasound in the near field. The spatial peak pressure amplitude was 0.2 MPa. The enhancement of cell destruction due to Optison was shown to be much higher than that due to Albunex for similar bubble concentration and ultrasound conditions. For toneburst exposures, significant lysis and sonoporation only occurred in the presence of a contrast agent. The majority of the bioeffects observed occurred in the first 5 min of exposure. The relationship between the enhancement of bioeffects and duty cycle of toneburst ultrasound appears to indicate that both stable gas spheres of contrast agents and cavitation nuclei created by the disruption of the gas spheres play a significant role in causing the bioeffects.
A calculation of the flow resistivity in intermediate flow regime
Authors: Picard Lopez M. A. , Solana Quiros P. E. , Arizo Serrulla J. V.
Published: July 2002

Many of the acoustic properties of fibrous materials can be modeled and predicted with the aid of appropriate empirical formulas. Among the input parameters that are required by such types of macroscopic models, the flow resistivity is a very well-established quantity in the literature, as usually this parameter is measured in steady Poiseuille flow conditions, i.e., at comparatively low flow speeds. One major concern with respect to such a parameter is the question of its possible frequency dependence. From a theoretical point of view, we have examined to which extent the capilar pore approximation can be utilized in intermediate flow regimes. The tendency towards lower values of flow resistivity for increasing acoustic Reynolds number also appears in all samples studied. And only the greater density samples, for the tested frequencies, were found in the flow regime of Poiseuille. However, if we want to obtain the value of the flow resistivity, for any sample, the employed experimental procedure makes it possible by a relationship between the experimental values and those of the Biot function. The value of the flow resistivity in different dynamical flow regimes to that of Poiseuille can be obtained.
Normal incidence sound absorption coefficient measurement using sound intensity technique: An accuracy investigation
Authors: Dimon Mohamad N. , Said Ahmad K. , Ibrahim Md. N. , Jaafar Md. Y.
Published: July 2002

Sound absorption data are required in specifying and proposing the correct materials for room acoustic treatment. However, there are instances where noncommon materials such as direct piercing carved wood panels (dpcwps) are used without sound absorption data. Sound absorption measurements obtained using an impedance tube and reverberation chamber are not accurate for dpcwp. This is primarily because the wall backing the dpcwp during the measurements constitutes the carved surface, which does not exist in actual installation. Therefore, an alternative measurement technique using a sound intensity measurement technique is more appropriate for dpcwp. This paper focuses on experimental methodology where various aspects need to be taken into consideration to achieve accurate results. Various criteria affecting measurement instruments’ capabilities and other factors affecting sound intensity measurement accuracy will be discussed. Sound absorption measurement was conducted on three different perforation panels which resemble dpcwp and it was found that the sound absorption measured with a deviation from an average value of −5.59% to 5.95% can be achieved, and is particularly accurate.
Low-frequency ILD elevation cues
Authors: Algazi V. Ralph , Avendano Carlos , Duda Richard O.
Published: July 2002

It is well known that the binaural ITD (interaural time difference) and ILD (interaural level difference) are the primary cues for azimuth, while monaural spectral features due to pinna diffraction are the primary cues for elevation. Pinna cues appear above 3 kHz, where the wavelength becomes comparable to pinna size. However, it is shown that there are also important low-frequency ILD elevation cues primarily due to torso diffraction. In the experiments reported, random noise bursts were filtered by individualized head-related transfer functions, and four subjects were asked to report the elevation angle. Eight conditions were tested, depending on whether the source was in front or in back, in the median plane or on a 45-deg cone of confusion, and had wide bandwidth or was band limited to 3 kHz. For the band-limited signal, localization accuracy was at chance level in the median plane, and was poor in front. However, at 45-deg azimuth in the back, the accuracy was close to that for a wideband source, the average correlation coefficient being approximately 0.75 for the narrow-band source and 0.85 for the wideband source. A physical explanation for the cues is presented. [Work supported by NSF under Grant No. IRI-9619339.]
Computational auditory scene analysis-constrained array processing for sound source separation
Authors: Drake Laura A. , Rutledge Janet C. , Katsaggelos Aggelos
Published: July 2002

In this work, techniques are developed and studied for the extraction of single-source acoustic signals out of multi-source signals. Such extracted signals can be used in a variety of applications including: automatic speech recognition, teleconferencing, and robot auditory systems. Most previous approaches fall into two categories: computational auditory scene analysis (CASA) and array signal processing. The approach taken here is to combine these complementary techniques into an integrated one: CASA-constrained array processing. In principle, this integrated approach should provide a performance gain since the information used by array processing (direction of propagation through a sound-field) is independent of other CASA features (fundamental frequency, on/offset, etc.). One difficulty encountered by CASA that can be overcome by array processing is the sequential grouping of spectrally dissimilar phonemes in a speech signal, such as a fricative followed by a vowel. The method presented here differs from standard array processing by the addition of CASA features for the signal separation decision. Compared to other CASA systems that use binaural cues, it: (1) is not limited to two microphones (since the goal is not auditory system modeling); and (2) makes complete use of source location and other CASA features—for simultaneous and sequential grouping.
Estimation of minimum glottal flow using optimal, low-pass filtering
Authors: Qi Yingyong , Hillman Robert E.
Published: July 2002

The amount of minimum glottal flow in each period of a sustained phonantion is an important parameter in voice research and clinic. In many cases, it is highly desireable to be able to measure the minimum glottal flow automatically. Here, we present a method for estimating the minimum glottal flow using an optimal, low-pass filter. The cutoff frequency of the low-pass filter is determined so that the sum of the variance within each ‘‘closed’’ phase of a recorded flow signal and the difference between the recorded and filtered flow signals is minimal. The minimum glottal flow is derived from this optimally, low-pass-filtered signal. This simple optimization procedure results in a complete automatic estimation of minimum glottal flow. Experiments using synthetic and real flow signals indicated that the method is highly accurate and robust.
Vocal fundamental frequency drop during VCV productions in Japanese speakers
Authors: Kariyasu Makoto , Michel John
Published: July 2002

Vocal fundamental frequency (fo) drop in relation to changes in intraoral pressure (Po) was investigated for adult male and female speakers of Japanese producing /b/ and /v/ in VCV contexts. Three experiments were conducted to examine the following effects on fo drop: (1) vocal tract constriction, (2) vowel context, and (3) speech rate. The results showed that the fo drop from vowels to a consonant was greater for /aba/ than for /ava/; it was greater for high vowel contexts, /ibi/, /abi/, /iba/, than for a low vowel context, /aba/. Speech rate changes with metronome and self-paced had variable effects on the fo drop. Overall, the fo drop for /aba/ ranged from 4% to 13% or from 0.75 to 2.17 semitones. Comparisions with English speakers will be reported. Effects of gender, vocal pitch, and intensity levels, and accent may be discussed.
Principal components analysis of x-ray microbeam pellet positions
Authors: Beaudoin Robert E. , McGowan Richard S.
Published: July 2002

Sets of pellet coordinates from the X-ray Microbeam Speech Production Database, each corresponding to a static articulatory configuration, are submitted to a principal components analysis. Several talkers are analyzed separately, and various criteria are used to select the times in the continuous speech data from which to extract pellet data. In some instances, all of a talker’s speech data are submitted to an automatic procedure intended to select syllable nuclei, based on Mermelstein’s algorithm [P. Mermelstein, J. Acoust. Soc. Am. 58, 880–883 (1975)]. In other instances specific data are chosen by hand according to utterance type (e.g., vowel, glide, and consonant–vowel transition). These analyses are intended for use in a project to recover articulation from speech acoustics. In particular, we examine the relationship between pellet positions from data, the tongue shape reconstructed from the principal components analysis, and the parameters of a simple acoustic tube model, which is derived from the Stevens and House model [K. N. Stevens and A. S. House, J. Acoust. Soc. Am. 27, 484–493 (1955)]. [Work supported by Grant NIDCD-01247 to Sensimetrics Corporation.]
Kinematics of compensatory vowel shortening: Intra and interarticulatory timing
Authors: Shaiman Susan
Published: July 2002

The acoustic shortening of vowels has been demonstrated to occur across a variety of contextual variations. The current study examined the kinematic adjustments involved in vowel shortening, as a function of speaking rate and coda composition (singleton consonants versus consonant clusters). Five normal speakers repeated the syllables /paep/, /paeps/, and /paepst/, embedded in a carrier phrase, across three distinct speaking rates (slow, normal, and fast). Changes in the timing of the jaw-closing gesture for post-vocalic bilabial production, and in the upper lip–jaw timing relationship (measured via phase angles), were examined. The onset of the jaw-closing gesture typically shifted earlier in the cycle of jaw movement for consonant cluster productions, across all speaking rates. Subject-specific modifications of interarticulator timing were observed, with some speakers adjusting upper lip movement in order to maintain constant timing with the jaw, while others tended to dissociate the upper lip and jaw. Both coda composition and speaking-rate manipulations resulted in substantial intersubject variability in the lip–jaw timing relationship. These findings suggest that, in order to achieve the intended acoustic-perceptual goals, articulatory coordination may not be absolutely invariant, but rather, systematically and individually organized across task manipulations. [Work supported by CRDF-University of Pittsburgh and NSERC.]
Commonality in the dorsal articulations of English vowels and liquids
Authors: Gick Bryan , Kang A. Min , Whalen D. H.
Published: July 2002

Phonological studies have predicted that the dorsal articulations of English /r/ and /l/ correspond with those of schwa and open o, respectively [Gick, Phonology (in press)]. Specifically, /r/ and schwa are hypothesized to share pharyngeal configuration, while /l/ and open o share upper pharyngeal/uvular configuration. To test this prediction, midsagittal MRI images of the vocal tract of a male speaker of American English were collected and midsagittal distance (of airspace above the tongue surface) measured at 44 3-mm intervals along the vocal tract length. Regions of the vocal tract were defined as pharyngeal, uvular and oral, as in Whalen et al. [JSLHR (in press)], with the pharyngeal region divided into upper and lower halves. Midsagittal distances were collected for eleven sustained vowels plus /r/ and /l/. Distances for average vowels were subtracted point by point from /r/ and /l/ and a single rms calculated within each region of the vocal tract. As predicted, in the upper pharyngeal and upper pharyngeal/uvular regions, /l/ showed the greatest correspondence with open o, while /r/ was most similar to schwa throughout the pharynx. These results support the phonological interpretation of the dorsal gestures of English liquids as vocalic. [Work supported by NIH grant DC-02717.]
Acoustic modification in English place assimilation
Authors: Gow David W. , Hussami Peter
Published: July 2002

Recent behavioral research suggests that listeners hearing words containing segments that have undergone place assimilation are able to recover the underlying form of the modified segment and anticipate the place of the segment that triggers assimilation. The present study contrasts acoustic place cues in unmodified coronals, assimilated underlying coronals, and underlying noncoronals in connected read speech in an attempt to characterize the nature of acoustic modification produced by place assimilation, and to understand how a single segment might encode the places of articulation of two segments. Adult male and female speakers produced triplets of sentences showing this three-way contrast across a variety of consonants and vowel contexts. Acoustic measures examined formant transitions and relative amplitudes. The implications of the results of these analyses for the the structure of acoustic categories for place information and the abstract representation of place are discussed.
Speech intelligibility and vowel production in persons with dysphagia
Authors: Bell-Berti Fredericka , Scott Diane M. , Kachmarchyk Rita , Colodny Nancy M.
Published: July 2002

Neurologically based dysphagias are often accompanied by dysarthria or apraxia. Dysarthrias have traditionally been identified perceptually, rather than with more objective instrumental measures, and vowel articulation is examined only rarely in dysarthria evaluations. It is possible that some speakers with neurologically based dysphagia have sub-clinical disturbances of speech that affect vowel as well as consonant production. This preliminary report examines the speech intelligibility and acoustical measures of vowel productions in a group of dysphagic subjects. Our goal is a better understanding of the relations between the dysphagia and the dysarthria. [Work supported by St. John’s University.]
Structure of phonetic categories produced by general learning mechanisms
Authors: Lotto Andrew J. , Holt Lori L. , Kluender Keith R.
Published: July 2002

The development of categories for complex auditory stimuli is an interest for both studies of general category learning and language acquisition. Previous work [Kluender et al., J. Acoust. Soc. Am. 104, 3568–3582 (1998)] demonstrated that avian species can learn to respond differentially to sounds from two vowel categories and the structure of their responses correlate well with human adult ratings of the vowels. In the current study, Japanese quail (Coturnix japonica) were trained to respond to either members of an /i/ or /ε/ distribution and to refrain, in both cases, from responding to members of an /I/ and /æ/ distribution. Birds responding to /ε/ (surrounded by /I/ and /æ/ in the vowel space) showed a prominent peak or ‘‘prototype’’ in their responses. Birds responding to /i/ (extreme in the vowel space) showed a weak or no ‘‘prototype,’’ but showed a strong gradient with response rate increasing for tokens further away from the other vowel distributions in the F1–F2 space. These data demonstrate that internal structure of (phonetic) categories is strongly influenced by relations to the competing stimulus set (vowel space). This is particularly important for theories of categorization or language acquisition that rely heavily on the existence of a ‘‘prototype.’’
Influence of fundamental frequency on stop-consonant voicing perception: A case of learned covariation or auditory enhancement?
Authors: Holt Lori L. , Lotto Andrew J. , Kluender Keith R.
Published: July 2002

Listeners labeling members of an acoustic series modeling VOT (e.g., /ba/-/pa/) are more likely to identify tokens with higher f0 as voiceless than they are for otherwise-identical tokens with lower f0s. This pattern of results may arise because a high f0 enhances perception of voicelessness, in line with auditory enhancement accounts of speech perception. Alternatively, because f0 and VOT covary in English production, it is possible that listeners respond in this manner due to experience with VOT/f0 covariation in the speech signal. The present investigation was designed to tease apart the relative contributions of these two potential mechanisms. Japanese quail (Coturnix coturnix japonica) were trained to ‘‘label’’ stimuli drawn from VOT series by pecking a key. During training, each quail experienced one of three styles of VOT/f0 covariation. For one group of quail, VOT and f0 covaried naturally with voiceless series members having higher f0s than voiced members. Another group of quail heard the inverse, ‘‘unnatural’’ covariation. A final group experienced stimuli for which there was no covariation between VOT and f0. Results indicate that experience with VOT/f0 covariation is the predominant force in shaping perception. Thus, general learning mechanisms may account for this symmetry between perception and production.
Wavelet parameters for speech synthesis
Authors: Tuttle Brian C. , Janota Claus P.
Published: July 2002

A standard method of analyzing human speech is to divide it into its constituent phonemes. Synthesizing speech from these phonemes without including the effects of coarticulation, however, can result in discontinuous and sometimes unintelligible sounds. A recently proposed model for the analysis of speech coarticulation uses wavelet system characterization where wavelet transforms describe the time-frequency behavior of a signal’s transmission channel. The objective of this research is to verify the proposed model by synthesizing the original speech from its analysis. The coarticulated speech in question is the consonant–vowel–consonant combination that occurs in words such as ‘‘deed’’ or ‘‘bib’’ where the two consonants are the same. These words along with their vowels spoken in isolation are recorded digitally and processed using the wavelet system model. The result is an analysis of the coarticulated word with respect to its vowel. The analysis shows in time and frequency how the vowel changes when spoken in context. Synthesizing the speech using the inverse process serves to verify the model. Comparing the result to the original speech reveals that the accuracy is determined mainly by the scale resolution of the wavelet transforms.
Application of the discrete wavelet transform (DWT) to the enhancement of pulmonary breath sounds
Authors: Forren J. F. , Gibian G. L.
Published: July 2002

Aural evaluation of pulmonary breath sounds, or auscultation, is a critical part of diagnosis and management in Pulmonary and Critical Care Medicine. However, reliability between examiners within an institution or across institutions is low. A study by Wilkins et al. of 277 North American physicians at the American College of Chest Physicians 1988 annual meeting revealed great inconsistencies in interpretation of breaths sounds. Normal breath sounds were identified as normal by only 80% of these physicians. In addition, variable interpretations were provided for patients with inspiratory and expiratory crackles as well as those with stridor. Clinicians had difficulty defining rhonchi and often misclassified them as wheezes. The algorithm, based on nonlinear operations on the DWT coefficients, makes adventitious features of lung sounds easier to hear. The algorithm makes both coarse and fine crackles much more clearly audible by suppressing the breath and other interfering sounds. While the processed stridor sounds less like stridor than before, the processing makes it easier to hear the difference between stridor and wheezes and thus aids in distinguishing vocal cord dysfunction from asthma. [Work supported by N.I.H.]