bluuebunny/crossref_metadata_2025 huggingface dataset:
Why is the 2f1−f2 distortion product maximum at f2/f1≊1.2?
Authors: Allen Jont
Published: October 2005

It has been known for a long time that the acoustic distortion product 2f1−f2 measured in the ear canal is maximum when f2/f1≊1.2. It is now known that all the distortion products f2−n(f2−f1), for integer n, peak at the same frequency fmax(f2), that depends only on f2. Neural tuning curves frequently have a notched region where the tip meets the tail. The frequency of this notch is defined as fz(fCF). Here, fz depends on the characteristic frequency of the neuron fCF. Assuming that the distortion products are generated on the basilar membrane at the f2 place, fCF is associated with f2. When this is done, it is found experimentally (for the cat) that fz=fmax. In other words, it has been found experimentally that the maximum of the DP is at the same frequency as where the tuning curve tail and tip meet. This result implies that the micromechanics of the cochlea contains a mechanical circuit resonance at this frequency. This impedance must be connected across the inner hair cells, so that it ‘‘shorts out’’ the nerve excitation, reducing the IHC sensitivity at the resonance frequency, and inseries with the nonlinear generator, thereby maximally coupling the DP back into the cochlear fluid, and hence into the ear canal.
Relaxation time constants for the suppression of spontaneous otoacoustic emissions by multiple ipsilateral tones.
Authors: Sun C. , Murphy W. J. , Long G. R. , Talmadge C. L. , Tubis A.
Published: October 2005

Previous investigations of the time constants associated with suppression and recovery from suppression of spontaneous otoacoustic emissions (SOAEs) by pulsed external tones have shown that limit-cycle-oscillator models of SOAEs provide a basis for qualitative and quantitative interpretation of SOAE behavior [Talmadge etal., MechanicsandBiophysicsofHearing, edited by P. Dallos etal., pp. 235–242 (1990)]. The Van der Pol limit-cycle oscillator model is generalized to the case of two external driving tones, one continuous and the other pulsed. The continuous tone introduces a suppressed SOAE amplitude that is further modulated by the pulsed suppressor component. The model predicts that suppression onset and recovery times will increase with increases in the amount of suppression from the continuous suppressor tone. Preliminary data indicate that the onset and recovery times are affected in the manner implied by the model. [Work supported by NIH-NIDCD Grant No. DC 00307.]
Transient behavior of flue organ pipes.
Authors: Hirschberg A. , Wijnands A. P. J. , Fabre B.
Published: October 2005

In earlier studies by Fletcher [Acustica 34, 224–233 (1976)], Nolle [J. Acoust. Soc. Am. 66, 1612–1626 (1979)], and Angster and Miklos [Proc. 13th Int. Conf. on Acoust., Vol. 3, 99–101 (1989)] crucial parameters determining the transient behavior of a flue organ pipe have been identified. In particular the jet width to mouth height ratio, the labium position relative to the jet center line, the size of the ears, and the steepness of the supply pressure rise appeared to be very important. It is interesting to relate the effect of these parameters to four fundamentally different sound production processes that occur successively in the course of the transient: (a) the variable volume flux through the flue as a consequence of the supply pressure rise, (b) the impulsive vortex shedding occurring when the jet hits the labium for the first time, (c) the jet oscillation controlled by an edge-tone feedback mechanism (Biot–Savart induction), and (d) the jet oscillation controlled by the acoustical response of the pipe (pipe tone). After a discussion, based on flow visualization and internal pressure measurements, a simplified model is presented. The model assumes that the transient is dominated by the variable volume flux (a) and the acoustical response of the pipe (d). The jet oscillation and jet–labium interaction are described with a modified version of Fletcher’s intuitive theory.
Musical dynamic levels of pipe organ sounds.
Authors: Hall Donald E.
Published: October 2005

The pipe organ offers the opportunity to conduct psychoacoustic experiments in which the sound of a natural instrument can be perfectly steady and reproducible. This study took advantage of the pipe organ to concentrate on that aspect of musical dynamics determined by the physical parameters of steady sounds, leaving aside the admittedly important effects of other variables such as context and articulation. Juries of musicians and music students provided judgments of musical dynamic levels produced by steady sounding of various stops and combinations on two pipe organs. Sound spectra from these organs have previously been analyzed in 1/3-octave bands [D. Hall, J. Acoust. Soc. Am. Suppl. 1 85, S141 (1989)]. Results of this study are compared with the hypothesis that loudness calculated by a procedure such as Zwicker’s will be a good predictor of the steady aspect of musical dynamic strength, while a simple unweighted sound level in dB is rather poor.
A technique for assessing spectrally analytic and synthetic binaural processing.
Authors: Dye R. H. , Stellmack M. A.
Published: October 2005

The ability to detect interaural delay in a low-frequency target tone is hindered by the presence of diotic distractors even when target and distractors are spectrally remote. One putative source of this interference is spectral integration of binaural information arising from target and distractor components. The aim of the current study is to examine the extent to which listeners have access to information regarding which delay is associated with which spectral component. The two components were 553 and 753 Hz, with one designated as the target and the other as the distractor. The duration of the tones ranged from 50 to 400 ms, with the targets and distractors gated simultaneously. For each block of 100 trials, the target and the distractor were presented at ten different interaural delays that ranged from left leading to right leading. Each possible pairing of target and distractor delay was presented once (in a random order) during each block of trials. A cue interval, consisting of a diotic presentation of the target component, preceded each test stimulus. Subjects were instructed to indicate whether the target component appeared to the left or right of the intracranial midline. Left–right judgments were plotted as a joint function of the target (x axis) and distractor delays (y axis). At a duration of 400 ms, most subjects produced left–right judgments that indicated spectrally analytic binaural processing: left–right judgments were partitioned by a vertical line passing through x=0. At shorter durations, left–right judgments indicated spectrally synthetic processing: left–right judgments tended to be partitioned by the diagonal y=−x. [Work supported by NIH.]
Additive versus multiplicative combination of differences of interaural time and intensity.
Authors: Tao Samuel H. , Stern Richard M.
Published: October 2005

Predictions of the position-variable model [R. M. Stern, Jr. and H. S. Colburn, J. Acoust. Soc. Am. 64, 127–140 (1978)] are compared to the observed lateralization of bandpass noise as a joint function of differences of interaural time, intensity, and phase (ITD, IID, and IPD, respectively) [T. N. Buell and C. Trahiotis, J. Acoust. Soc. Am. 90, 2266 (A) (1991)]. This presentation is primarily concerned with the effect of IIDs on the lateralization of bandpass noise. It is shown that the multiplicative intensity-weighting function that had been a feature of all previous implementations of the position-variable model is fundamentally unable to describe the data of Buell and Trahiotis. It is argued that the form of these data suggests that the effects of IID must be introduced in an additive fashion at a more central level, after image position is estimated on the basis of timing information alone. Such a model provides a very good description of the Buell and Trahiotis data, as well as the results of several classic studies of time-intensity trading. Also discussed are the general implications of these data in terms of peripheral and central theories of time-intensity interaction. [Work supported by NSF.]
Discrimination of various movement patterns.
Authors: Perrott David R. , Constantino Brian , Ball Jennifer , Cisneros John
Published: October 2005

The ‘‘snapshot’’ hypothesis [D. W. Grantham, J. Acoust. Soc. Am. 79, 1939–1949 (1986)] suggests that velocity is simply inferred. Subjects are assumed to be utilizing information regarding both the distance traveled from signal onset to offset and the temporal extent of the interval during which movement occurs. A number of motion patterns were examined in the current series of experiments with particular attention to whether subjects could discriminate between sequences in which both the distances traveled and the duration of the events were identical. As a case in point, subjects were able to discriminate between acceleration and deceleration movement patterns. The implications of these results will be discussed. [Work supported by NSF.]
Binaural sound localization using neural networks.
Authors: Craig Rushby C. , Anderson Timothy R.
Published: October 2005

Artificial neural networks (ANNs) were used as a tool to localize sound sources from simulated, binaural signals. The sound sources for the experiments were restricted to a circle of radius 9 ft, centered about the head and lying on the horizontal circle. Sound source positions were randomly selected from one of the 360, one-deg increments on the circle. Classes for the ANNs were created by dividing the circle into equally sized wedges, much like slices of a pie. The number of classes used in the experiments varied from 4 to 36. Two types of sound source signals were considered: tones and Gaussian noise. Three different feature sets were tried. Results will be presented that compare the performance of the three feature sets for each sound source type. The best feature set produced similar results in terms of localization accuracy on tones and Gaussian noise (over 91% for 18 classes). Observations were made of phenomena which also occur in human psychological experiments such as front–back confusions and increased difficulty in localization below 1500 Hz.
Test–retest reliability of distortion product otoacoustic emissions in normal-hearing and hearing-impaired adults.
Authors: Halling Dan C. , Humes Larry E.
Published: October 2005

Distortion product otoacoustic emissions (DPOAEs) were measured in the ears of 25 normal-hearing and 25 hearing-impaired adults to assess test–retest reliability. Primary tones with geometric mean frequencies of 1, 2, and 4 kHz (f2/f1=1.21) were utilized. Results for the normal-hearing adults indicated that test and retest DPOAE detection thresholds for each ear were highly correlated at 1 kHz (r=0.81), but only moderately correlated at 2 and 4 kHz (r=0.53 and 0.48, respectively). DPOAE amplitude at various suprathreshold input levels was also evaluated for test–retest reliability. DPOAE amplitudes at all input levels and frequencies showed at least a moderate correlation, with the strongest seen at 1 and 4 kHz with 75 dB input (r=0.85). Of the two DPOAE measures, detection threshold and amplitude, the latter appears to be most stable over successive measurements in normal ears. The data from the hearing-impaired listeners will be used to explore further the reliability and validity of the use of DPOAEs as a clinical measure. [Work supported by NIH.]
Approximate methods for reflection from solid bottoms.
Authors: Zhang Z. Y. , Tindle C. T.
Published: October 2005

The acoustic reflection coefficient for a solid ocean bottom can be well approximated by assuming an ‘‘equivalent fluid’’ bottom of suitably chosen parameters. The density and attenuation of the equivalent fluid are different from the corresponding parameters of the solid. In particular, the density is substantially smaller and it is shown that simple neglect of the shear wave parameters of the solid can give poor results. The equivalent fluid can be used for both normal mode and ray calculations of the field in the water and gives essentially the same results as calculations that include the full shear waves effects. For isovelocity water, bottom reflection can also be modeled by assuming a perfect reflector at an ‘‘effective depth.’’ A new complex effective depth is defined to account for energy loss due to attenuation and the generation of shear waves. The resulting normal mode parameters are also complex. The sound field in shallow isovelocity water can be found very accurately and rapidly using the complex effective depth approach.
The effective depth approximation for sound propagation in shallow water over a sediment layer and a hard rock basement.
Authors: Glegg Stewart A. L.
Published: October 2005

This paper considers an effective depth approximation for an ocean waveguide with a bottom in which a sediment layer overlies a hard rock basement. The primary application of this approximation is to the calculation of three-dimensional propagation over sloping bottoms. It is shown that at low frequencies the resonances in the sediment layer cause the effective depth to oscillate rapidly. At high frequencies, when the attenuation in the sediment layer becomes significant, the effective depth tends to zero and the acoustic propagation is dependent on the modal attenuation. This can be incorporated into the effective depth theory by allowing the effective depth to be a complex number, defined in terms of the impedance of the water/sediment interface. Comparison with exact calculations shows that the effective depth approach gives a good approximation for the lower-order modes, but does not include the effects of the higher-order modes which are shown to make a significant contribution to the fine scale structure of the long range transmission loss. [Work supported by ONR.]
The influence of seabed properties on the generation and propagation of Scholte interface waves.
Authors: Ali Hassan B.
Published: October 2005

Scholte seismic interface waves can be an important component of very low-frequency (VLF) acoustic propagation, particularly in shallow-water environments. Under certain conditions, these waves may provide the only effective mechanism for the propagation of VLF energy. Moreover, they are often a significant, if not dominant, contributor to the VLF/ULF ambient noise field, both seismic and waterborne components. This work examines the generation and propagation mechanisms of Scholte waves using the results of recent NOARL measurements and new numerical predictions. It is shown that the propagation characteristics of these seismic waves, including their presence in the water column, are dependent not only on the bottom geoacoustics (particularly shear speeds) but also on the types and thicknesses of layers overlying the basement level. The measurement of Scholte waves even in the apparent absence of near-bottom sound sources suggests the excitation of secondary Scholte waves by the roughness of the seabed in the vicinity of the receiver. In particular, these secondary Scholte waves are attributed to the conversion into shear (S) waves of incident waterborne compressional (P) waves. Conditions favoring such P to S conversions, and the implications for acoustic propagation, are discussed. [Work supported by ONR.]
Wave conversion in cross sections of a weakly inhomogeneous waveguide.
Authors: Starkov Alexander S.
Published: October 2005

Acoustical waves propagation in a low-speed layer of variable depth based on a fluid bottom is considered. The depth and sound velocities in the layer and bottom vary slowly with horizontal distance. Traditional adiabatic expansion breaks down in the cutoff region. Here, the goal is to investigate wave conversion in tapered and broadened waveguides. In the first case, the lateral wave is created in every critical cross section [A. S. Starkov, Akust. Zh. 36, 348–354 (1990)]. Therefore, at cutoff the normal wave mode creates a secondary lateral wave. Similarly, in the case of a broadened waveguide the lateral wave creates a normal mode. The fields in the transition region are obtained with various asymptotic methods and described in terms of Airy and incomplete Airy functions. The coefficients of different waves excitation are calculated. It is shown that the curvature of the boundary leads to the more complicated Fock type expansions. The resulting wave fields are shown to have additional oscillations before cutoff and decrease slowly after cutoff.
Clinical relevance of scattering.
Authors: Thieme Gary A.
Published: October 2005

Diffuse scattering is the basic sound interaction responsible for the soft tissue detail seen in modern clinical gray scale ultrasound imaging. Its counterpart is specular reflection which is the physical interaction responsible for the bright interfaces seen in bistable and modern images. This paper will illustrate the effects of operator-controlled system variables on the image generated from diffuse scattering processes and will demonstrate the clinical aspects of diffuse scattering through the use of tissue-mimicking phantoms and normal and pathologic clinical imaging examples. Four parameters (spatial resolution, contrast resolution, texture, and speckle) influence our ability to detect focal lesions and diffuse pathologic abnormalities in the clinical setting. Signal processing in the ultrasound system and adjustment of controls by the operator affect the perception of diffuse scattering. Imaging is influenced by transducer frequency and focusing characteristics, system gain, time gain compensation, system dynamic range, preprocessing functions, post-processing functions, system power, and frame averaging. Images illustrating the effects of these parameters will be shown.
Measurement system effects in ultrasonic experiments.
Authors: Waag Robert C. , Astheimer Jeffrey P.
Published: October 2005

Arbitrary fields are represented as angular spectra of plane waves and arbitrary time waveforms as frequency spectra of temporal harmonics in an integral expression that includes instrument effects on the spectrum of the scattered pressure. A transformation of variables yields a form convenient for interpretation. Simplified expressions are developed for the effect of beam patterns when the detector time gate has an infinite duration. Simplified expressions are also developed for the effect of the emitter waveform and detector time gate using a narrow-band approximation and for the effect of the emitter beam and detector sensitivity patterns using a quasi-plane-wave approximation. The simplifications yield insightful forms for measurement system characteristics and these forms are evaluated analytically for Gaussian spatial apertures and Gaussian temporal waveforms. Numerical evaluations of general expressions for the weight of Gaussian, exponential, and uniform spatial apertures are also given. The results indicate instrumentation parameters that can be employed to measure intrinsic characteristics of a scattering medium and may be used to design experiments from which intrinsic parameters of scattering media are obtained.
Reflections and emissions from stones during electrohydraulic lithotripsy.
Authors: Delmenico P. R. , Rabbitt R. D.
Published: October 2005

Lithotripsy is a noninvasive procedure to destroy biliary and renal concretions using shock waves generated externally to the patient and focused at the stone site. The effectiveness and safety of lithotripsy procedures are partially determined by the accuracy of stone targeting. The presentation will cover analysis of pressure waves reflected from the stone to determine stone location, degree of pressure wave focusing, and stone geometry (with changes in stone geometry providing a measure of stone destruction). In the experiments, a Wolf model 2137.50 electrohydraulic lithotripter is used in conjunction with an ellipsoidal focusing system. Piezoelectric pressure transducers within the focusing system provide a means to measure pressure waves both before and after reflection from a variety of targets. In addition, a computer simulation for axisymmetric shockwave propagation in an ellipsoid is developed to predict reflections from stones of arbitrary geometry and position relative to the far focus of the ellipsoid. This ray method solution of the high-frequency approximation to the wave equation accounts for the formation of caustics, while other nonlinear effects are neglected. The simulation allows the visualization of time varying pressure fields within the lithotripter focusing system and around the targeted stone. This research could provide a starting point for a method of dose estimation in lithotripsy procedures. [Work supported by NSF, BCS-8957206.]
Sizing of microbubbles by nonlinear scattering.
Authors: Chen Xucai , Meltzer Richard S.
Published: October 2005

A technique to determine the size distribution of microbubbles in echo contrast agents is presented. The experimental apparatus consists of three confocally positioned acoustic transducers, two of which serve as transmitters and the other serves as a receiver. One transmitter transmits tone bursts at a fixed frequency higher than the resonance frequencies of the microbubbles, while the other transmitter transmits tone bursts whose center frequencies are swept through the range of resonance frequencies of the microbubbles. Scattered tone bursts are detected by the receiver and recorded by a digital oscilloscope and a computer. A two-dimensional power spectrum is obtained by calculating the spectrum of the received signal as a function of the sweeping frequency. Amplitudes of the second harmonic of the sweeping frequency [D. L. Miller, Ultrasonics 19, 217–224 (1981)] as well as the combination frequencies [V. L. Newhouse and P. Mohana Shankar, J. Acoust. Soc. Am. 75, 1473–1477 (1984)] are used to calculate the size distribution of the microbubbles.
The origin of acoustic distortion in the cochlea.
Authors: Brown A. M. , Gaskill S. A.
Published: October 2005

Two-tone stimulation of the ear is a powerful tool for investigating cochlear function and is gaining increasing acceptance as an audiological test. The intermodulation distortion generated by two tones includes numerous cubic components. The behavior of cubic lower sidebands has been studied by measuring them with a microphone in human and rodent ear canals as the stimulus frequency was changed at various stimulus levels. It was found that distortion produced by low level stimuli (level of f2 at or below 40 dB SPL) is due to activity at the f2 region on the cochlear partition, and that the sound measured in the ear canal has passed through an additional cochlear filter (possibly the tectorial membrane). The picture may be complicated in the human ear by added energy from the distortion product frequency region. At high stimulus levels, the response is more difficult to interpret. There may be distinct sources of 2f1−f2 caused by secondary modulation of f1 by f2−f1 (f2−f1 belongs in the quadratic, rather than the cubic family). This interaction would also give f2 (thus enhancing or suppressing the f2 level, depending on phase relationship) and upper sidebands, such as 2f2−f1.
Otoacoustic emissions and auditory perception.
Authors: Long Glenis R.
Published: October 2005

The literature on the impact of otoacoustic emissions and their underlying mechanisms on the perception of sounds will be reviewed. Although stable spontaneous otoacoustic emissions are not normally heard, any rapid change in the frequency and level of an emission may cause it to be audible. Spontaneous emissions interact with external tones which may be responsible for some instances of monaural diplacusis. Otoacoustic emissions are associated with local minima in hearing thresholds measured with small frequency increments (threshold microstructure). Changes in the level and frequency of the emissions (occurring either naturally or during aspirin consumption and noise exposure) are correlated with changes in threshold microstructure. Frequency and intensity discrimination and perceived loudness of low level tones and nonsimultaneous masking of higher level tones are modified by the presence of otoacoustic emissions. Combination tones have been evaluated psychoacoustically for over 20 yr. Differences between psychoacoustic and otoacoustic estimates of combination tones will be discussed.
Phonetic underspecification in Marshallese.
Authors: Choi John D.
Published: October 2005

The vowels of Marshallese have been analyzed as contrasting only along the height dimension, variation along the front–back dimension being predictable by the secondary articulations of adjacent consonants. Spectrographic evidence suggests this analysis is correct and that the surface allophones can be derived by interpolating between C1 and C2 targets across a vowel that is unspecified for F2. To test this hypothesis, /C1VC2/ words (Cn={/pj/, /pveeswirl/, /tj/, /tveeswirl/} and V={/schwa/, /barred eye/, /a/}) were recorded from four speakers. Then F2 was measured from vowel onset to offset. Preliminary findings based on two of the speakers shows that while F2 variation at the vowel center is statistically significant as a function of vowel category, the proportion of variance accounted for by vowel category is very low compared to that accounted for by the secondary articulation of C1 and C2. This is interpreted as evidence that a vocalic F2 target may not be necessary in modeling the trajectory. Multiple linear regression tests support this interpretation, showing that the vowel midpoint can be accurately predicted without reference to a vowel target. Regression analysis was performed on 15 time-normalized points with and without an intercept k, where k represents an independent vowel contribution to F2. The results show that the contribution of k is negligible (±0.001). Data from the two remaining speakers will be incorporated and discussed in terms of phonetic underspecification in a target-interpolation model.
Focus in Peninsular Spanish.
Authors: Toledo Guillermo , Celdrán Eugenio Martínez
Published: October 2005

This study explored the acoustic realization of focus in several dialects of Mediterranean Peninsular Spanish. The materials consisted of two corpora of declarative sentences with differences of neutral versus broad versus narrow focus and neutral versus single versus dual focus triggered by wh-question contexts. For that goal values of focal prominence in three prosodic parameters, F0, duration, and amplitude, were investigated through intonation contours and digital spectrograms of seven male speakers’ emissions. The statistical analysis of the measurements has shown no acoustic differences among focused and unfocused items, and among sentences in the two corpora. The results provided support for prior studies in American and Canary Spanish which were undertaken through similar experimental designs. However, these data appeared to contradict the general findings reported elsewhere which have shown a higher degree of prominence in the marking of focus both in cognate languages like French and Italian and in Germanic languages.
Travel time corrections for ice scattering in the 1988–1989 Greenland Sea tomography experiment.
Authors: Lynch J. , Pawlowicz R. , Beliakova N. , Worcester P. , Guoliang Jin
Published: October 2005

Previous work by Guoliang and Wadhams [Prog. Oceanog. 22, 249–275 (1989)] has shown that reflections of acoustic rays by a sea ice cover can significantly affect acoustic travel times in an ocean tomography experiment. This can lead to warm or cold biases in the ocean inversions, if unaccounted for. This paper presents a discussion of how one deals with correcting the travel times of acoustic arrivals seen in the 1988–1989 Greenland Sea tomography experiment for ice effects. The discussions will include: generalization of the beam displacement formalism of Guoliang and Wadhams, determination of the reflection coefficient versus incidence angle of the rays using scattering amplitude data, estimation of beam displacements and time delays, and effects of the corrections on inversions for the ocean temperature field. Directions for future work will also be discussed. [Work supported by ONR and NSF.]
Inertial and geometrical properties of the human ossicles.
Authors: Setser R. M. , Rabbitt R. D.
Published: October 2005

The principle volume moments of inertia and corresponding directions were numerically evaluated from three-dimensional reconstructions of the human ossicles. The location of the center of volume for each ossicle was also determined. Results were combined with average density measurements in order to estimate the principle mass moments of inertia. Surface data for the reconstructions were obtained in the form of parallel plane sections using computer-interfaced video microscopy. Between 500 to 1500 (x,y,z) surface data points were recorded for each ossicle. Computation of the inertial and geometrical properties was greatly simplified through the use of integral kernels selected to reduce the volume integrals to surface integrals. Average results for two adult subjects provide the mass, volume, and principle mass moments of inertia for the malleus as m=25.0 mg, V=13.5 mm3, I1=94.1 mg-mm2, I2=9.1 mg-mm2, and I3=15.4 mg-mm2. For the incus m=25.7 mg, V=15.5 mm3, I1=119.8 mg-mm2, I2=107.8 mg-mm2, and I3=36.4 mg-mm2; and for the stapes m=3.0 mg, V=2.24 mm3, I1=6.79 mg-mm2, I2=5.36 mg-mm2, and I3=1.82 mg-mm2. Ossicle reconstructions are graphically displayed to illustrate the directions of the principle axes and the location of the center of volume of each ossicle. The computer-based surface models are also valuable in visualizing the geometry of individual ossicles and in providing geometrical data for use in middle ear models and prosthetic design. [Work supported by NSF BCS-8957206.]
Intensity coding using only low-spontaneous-rate auditory neurons.
Authors: Zeng Fan-Geng
Published: October 2005

A recent physiologically based model has shown that the optimal combination of rate information from both high-spontaneous rate (SR) and low-SR neurons predicts an intensity discrimination performance that exceeds human psychophysical performance across most of the normal range of intensity [I. M. Winter and A. R. Palmer, J. Acoust. Soc. Am. 90, 1958–1967 (1991)]. The present model, which uses only low-SR neurons and a suboptimal decision process, predicts the human psychophysical data over a 100-dB range. Rate-intensity functions of six low-SR neurons are constructed based upon a linear relation between the neural threshold (dB) and the SR in logarithmic units. Variances of firing rates are derived from a Poisson process modified by a 2-ms dead-time. The decision variable is the unweighted sum of the firing counts from the six low-SR neurons. The same model has also been applied to the power law of loudness growth function, the midlevel hump on forward-masked intensity discrimination, and the effect of notched noise on intensity discrimination. [Work supported by NIH.]
Acoustic response properties of single units and unit clusters in the midbrain of the goldfish.
Authors: Lu Z. , Fay R.
Published: October 2005

Single units and small unit clusters were recorded from the torus semicircularis (TS) of the goldfish using indium electrodes. Response areas (RA) were formed as iso-level, spike count functions (75 to 1250 Hz) at 5-dB intervals throughout the unit’s dynamic range. Spike count versus level functions and tuning curves were obtained from the RAs, giving characteristic frequency (CF), best sensitivity (BS), and Q10dB. Peri-stimulus time (PSTH), interval, and period histograms were determined at CF and other frequencies. Units fall into three clusters with CFs at about 150, 400, and 1000 Hz, as is the case for saccular afferents. Tuning tends to be sharper in the TS than in the periphery. Lowest BS as a function of CF corresponds closely to the behavioral audiogram. Inhibitory effects are suggested by nonmonotonic level functions and by suppression of spontaneous activity. Slopes of spike count versus level functions are steep near CF and much shallower above and below CF. The first units encountered in a dorso-ventral electrode track tend to be tonic, short latency, and phase lock as accurately as saccular afferents. These are often two-unit clusters with different CFs but with phase- locked spikes 180° out-of-phase. Encountered next are more phasic, longer-latency responses with little phase locking, and occasionally with complexly shaped PSTHs. The frequency at which iso-level functions peak is generally independent of level, unlike saccular afferents. Thus frequency is far better represented by spike rate in the TS than in primary afferents. [Work supported by a Center Grant from NIDCD.]
Windowed Fourier transforms−Application to structural acoustics.
Authors: McCoy John J.
Published: October 2005

The windowed Fourier transform provides the resolution of a (space/time) forcing of a linear dynamical system, using a set of base functions spanning a (space-wavelength/time-frequency) phase space. The elements of the set of base functions, separately chosen as fundamental forcings of the dynamical system, define a set of fundamental solutions from which the system response to an arbitrary forcing can be obtained by a process of synthesis. A specific characterization of the nature of the windowing, i.e., of the set of base functions for resolving the forcing, leads to a characterization of the set of fundamental solutions resulting therefrom, as a specific ‘‘species’’ of response functions. The recent experience of a number of different researchers of a broad range of problems is that one can achieve both physically intuitive and computationally efficient solution algorithms by choosing phase-space base functions that remain localized under the operation that obtains a system response from a system forcing. Three examples of application of these ideas will be presented. One is for the range evolution of a narrow-band acoustic field emanating from a source plane by a process of (physical space/direction) phase-space marching. The second is the propagation of a wideband signal through a dispersive waveguide. The third is the acoustic field radiated from a submerged plate subject to a forcing of compact support in both space and time. [Work supported by ONR.]
Segmental phonetic cues to language identity.
Authors: Flege James Emil , Munro Murray J.
Published: October 2005

In experiment 1, detailed acoustic analyses of 42 tokens of taco as spoken either in Spanish or English by monolinguals, and in both languages by early and late learners of English L2, were performed. As expected, the early learners’ renditions of taco in Spanish and English differed more than the later learners’. Correlation techniques revealed that the extent to which the bilingual talkers approximated English phonetic norms for the four segments in taco was interrelated, suggesting that the word is an important unit in cross-language phonetic interference. In experiment 2, three expert listeners identified the language in which the taco tokens had been spoken, then rated each for goodness. The Spanish and English monolinguals’ renditions of taco were readily differentiated, indicating that purely phonetic differences can cue language identity. The late learners’ English and Spanish renditions were judged to be only slightly different whereas the listeners tended to judge the early learners’ renditions as being clearly Englishlike or Spanishlike. Multiple regression analyses examining the acoustic variables from experiment 1 were able to account for most variance in the listeners’ identification judgments and goodness ratings (81%, 97%). In experiment 3, three acoustic parameters identified as significant predictors of the listeners’ perceptual judgments (viz., VOT of ‘‘t,’’ the spectral quality of ‘‘a,’’ and ‘‘o’’ duration) were varied from ‘‘Spanish’’ to ‘‘neutral’’ to ‘‘English’’ in synthetic versions of taco. All other parameters were set to the average of values observed for the Spanish and English monolinguals. The hypothesis was tested that language identification may be based on a single segment, whereas goodness ratings are based on properties distributed through the entire word.
Theoretical study of heat transport in thermoacoustic stacks having arbitrary plate separation.
Authors: Hofler Thomas J.
Published: October 2005

Thermoacoustic heat engines can be simply described as devices where heat transport is caused by the interaction between a standing wave and a stationary, parallel plate structure called the stack. Simplified calculations of this heat transport have been discussed previously, which assume perfect standing waves (infinite standing wave ratio) and plate separations that are large relative to a thermal penetration depth. A theory will be presented that is generalized to describe systems with arbitrary plate separation and SWR. Using this theory, the spectrum of heat engine designs that span ‘‘classic’’ thermoacoustic engines on the one extreme, and Stirling cycle engines on the other extreme, can be compared. Some results are that Stirling cycle engines can be more efficient than standard thermoacoustic engines and that, given some practical constraints, thermoacoustic engines can deliver more power than a comparable Stirling engine. Other results may help to design an improved engine that combines the characteristics of both thermoacoustic and Stirling engines. [Work supported by ONR and NRL.]
Vowel reduction and perceptual recovery in casual speech.
Authors: Manuel Sharon Y.
Published: October 2005

A pervasive characteristic of casual (normal conversation) English is the apparent deletion of unstressed vowels like the first vowel in the word ‘‘support.’’ One might suppose that if the first vowel in ‘‘support’’ were deleted, ‘‘support’’ would become homophonous with ‘‘sport.’’ Acoustic and physiological data are reported which suggest that in fact when speakers appear to be deleting an unstressed schwa, they are often actually omitting only the oral gestures for the vowel. The glottal gestures stay much as they are in careful speech and are tied to the remaining oral gestures much as they are in careful speech. Also reported are perceptual data which suggest that listeners are sensitive to the acoustic consequences of these residual patterns, and can use this information to distinguish between ‘‘sport’’ and reduced versions of ‘‘support’’ [see also J. Fokes and Z. S. Bond, J. Acoust. Soc. Am. Suppl. 1 85, S85 (1989); J. Fokes and Z. Bond, Proc. XII Int. Congr. Phon. Sci. 4, 58–61 (1991)]. These results will be discussed in terms of the more general issue of deletion and recovery of phonetic information. [Work supported by NSF.]
A review of the Parabolic Equation Workshop II.
Authors: King David B. , Chin-Bing Stanley A. , Davis James A. , Evans Richard B.
Published: October 2005

In Spring, 1981, the first Parabolic Equation (PE) Workshop was held [Davis, White, and Cavanagh, NORDA Technical Note 143 (1982)]. The purpose of that workshop was to provide a forum for theoretical and applied PE developers and to compare computer results for a set of ocean acoustic problems. Underwater acoustic modelers have benefited from that set of test cases and documented PE deficiencies for nearly a decade. The second PE workshop was recently held (in Spring, 1991) to document the impressive advances that have taken place in the development of PE models over that decade. PE developers from the ocean acoustics community were invited to provide computer solutions for a new set of ocean acoustic problems. The set of problems was designed to test the ability of PE models to handle (a) wide-angle propagation (nearly ±90° with respect to the axis of propagation), (b) shear waves and shear attentuations, (c) backscatter, (d) conservation of energy, and (e) complicated range-dependent environments. In addition, predictions from the PE models were compared with measured acoustic data taken in a region where the ocean environments (water column, sediment, ocean bottom, and subbottom) were well-known. Results from this PE Workshop II indicate that several significant advances have occurred in PE model development to the extent that some current PE models can include very wide-angle propagation, shear waves, and backscatter, while conserving energy. Additionally, an unexpected problem experienced by some wide-angle split-step PE models was also presented at the PE Workshop II. These and other results from the PE Workshop II will be presented and discussed. [Work supported by ONR AEAS and ONR Acoustic Reverberation SRP.]
Modal travel time and dispersion with an eddy lens (EL).
Authors: Shang E. C. , Wang Y. Y.
Published: October 2005

A special type of mesoscale eddy, called intrathermocline eddy or eddy lens (EL), has been studied intensively in oceanography over the past decades. The special features of the EL are (1) the deep warm core (near the sound channel axis), (2) the strong anomalies of sound speed (can be as large as 10–15 m/s), and (3) the long lifetime. The significant impact on acoustic wave propagation of EL due to these features is the ‘‘double channel’’ effect. In this paper, mode couplings caused by the ‘‘double channel’’ induced by EL is investigated. For ocean acoustic tomographic interest, modal travel time and modal dispersion are calculated by using the modal spectrum of the PE field (MOSPEF) method. Numerical simulation for a 57-Hz pulse with 10-Hz bandwidth is conducted. [Work supported by NOAA.]
On equations for the speed of sound in seawater.
Authors: Dushaw Brian D. , Worcester Peter F. , Cornuelle Bruce D. , Howe Bruce M.
Published: October 2005

Long-range acoustic transmissions made in conjunction with extensive environmental measurements and accurate mooring position determinations have been used to test the accuracy of equations used to calculate sound speed from pressure, temperature, and salinity. The sound-speed field computed using the Del Grosso equation [V. A. Del Grosso, J. Acoust. Soc. Am. 56, 1084–1091 (1974)] give predictions of acoustic arrival patterns which agree significantly better with the long-range measurements than those computed using the Chen and Millero equation [C. Chen and F. J. Millero, J. Acoust. Soc. Am. 62, 1129–1135 (1977)]. The predicted ray travel times and travel time error have been calculated using objectively mapped sound-speed fields computed from CTD and XBT data. Using the measured and predicted ray travel times, a negligible correction to Del Grosso’s equation of 0.05±0.05 m/s at 4000-m depth is calculated. Small errors of about 50 m in the GPS determination of mooring positions lends a depth-independent error of 0.1 m/s to the sound-speed equation correction. [Work supported by NSF and ONR.]
Architectural acoustics: Some pioneering and some prognostication.
Authors: Beranek Leo L.
Published: October 2005

Architectural acoustics, following Wallace Sabine in 1900, entered a new era after World War II. Measuring equipment was improved−new sound level meters, microphone calibrators, graphic level recorders, octave-band analyzers, and, soon, magnetic tape recorders. The National Bureau of Standards, the Riverbank Laboratories, and others had armed us with data on the absorption of sound by commercial acoustical materials and the transmission loss of standard walls. The broadcasting industry taught studio design with thin molded plywood surfaces. At the risk of delimiting the broader scope of the field, including noise control in building spaces, this paper reviews the very demanding area of room design for listening and performance of unamplified concert music, choral works, and opera. Recent studies have shown that an extraordinarily delicate balance exists among the many interrelated variables that comprise an optimum environment for music. The attributes of acoustics that must be satisfied in design, and several alternate architectural shapes of noteworthy recent halls are reviewed. An exciting new program, just underway by an international consortium of researchers and consultants, to systematically measure and document existing halls throughout the world is described.
Progress in environmental noise control.
Authors: Cavanaugh W. J.
Published: October 2005

Environmental noise, i.e., unwanted sound around and within the buildings in which people work and live, is an ubiquitous byproduct of mankind’s societal and technological development. Noise exposure of populations throughout the developing world gradually accelerated starting with the industrial revolution of the 19th century and increased dramatically with the population growth and introduction of new transportation and other sources during the 20th. In recent decades, people who sought the tranquility of suburban living were increasingly greeted with new industrial parks whose tenants also sought escape from decaying, no longer economically sound, urban locations. Even the return to regenerating city centers assures little relief from the noise of new highway, rail, and expanding airport developments or, for that matter, from noisy air conditioning equipment serving buildings nearby or from the sounds of one’s own building neighbors above, below, or next door. This paper reviews the last 40 or so years of what must be considered remarkable progress in dealing with the diverse challenges of environmental noise. In terms of the classical ‘‘systems’’ approach to noise control, the sources and transmission paths are now reasonably well developed and understood both in theory and in measurement. The effects of environmental sounds that ultimately reach the human receptors are less so, however. The continuing development of adequate criteria represents the significant remaining challenge in environmental noise control. This paper reviews some of the pioneering criteria developments for background noise and acoustical privacy in buildings and for community noise.
Acoustic and auditory evidence of sociophonetic variation in Vancouver: LTAS and vocalic data.
Authors: Esling John H.
Published: October 2005

Formant frequencies of ten Canadian English vowels from identical environments in reading style were calculated for 128 subjects in the middle and older age groups of the sociolinguistic Survey of Vancouver English. LPC-based F1, F2 distributions were derived using a computerized speech lab (CSL) program and evaluated statistically to identify differences in vowel quality across four socioeconomic-status (SES) classes for both sexes. Long-term average spectra (LTAS) of 60 s of reading text were also computed and compared with vowel formant results. The SDDD LTAS dissimilarity index (standard deviation of the differences distribution) was also applied to the 192 subjects in all (including young) age groups. Auditory evaluations of each subject’s production of each vowel were compared with the results of formant analysis and both LTAS analyses. Here, F1 values were more uniformly differentiated than F2, and some groups’ vowels were more vulnerable to rejection of F2 on bandwidth criteria than others. Differentiation is significant and consistent for a high proportion of vowel formant distributions for some SES groups, notably between working-class (WC) and middle-class (MC) middle-aged women. Some F1, F2 patterns are compatible with auditory predictions of a hierarchy of vocalic susceptibility to contrasting voice quality settings. [Work supported by SSHRCC.]