bluuebunny/crossref_metadata_2025 huggingface dataset:
On the phonetic/phonemlc status of /h/
Authors: Narty Jonas N. A.
Published: October 2005

A number of linguists have, over the years, classified the sound represented by the phonetic symbol [h] as a voiceless glottal fricative (e.g., Strevens, 1960). Others (notably, Ladefoged, 1975) have chosen to describe it as a glide or an approximant. It is the contention of the present author that neither of these descriptions gives a true phonetic classification of /h/. This author believes that calling /h/ a “voiceless vowel” is more accurate. To support this view the present author compared acoustic measurements of /h/ and (other) fricatives, glides as well as vowels of English. Also, two types of [h], one treating it as a “consonant” and the other as a voiceless vowel were synthesized and presented to native Amerian English speakers for “naturalness” judgments. Results showed that the [h] with the characteristics of a “voiceless vowel” was preferred as being more “natural” sounding in all environments.
Large amplitude compression and shear wave propagation in condensed materials
Authors: Gupta Yogendra M.
Published: October 2005

In the last few years experimental methods have been developed to produce and measure large amplitude one-dimensional compression and shear waves in impact experiments. Shear wave data have been obtained for materials ranging from elastomers (essentially liquids) to hard ceramics, like polycrystalline Al2O3. We can now measure “acoustic” longitudinal and shear wave velocities in the shocked region and better quantify the shocked state. For a certain class of materials, these measurements provide a complete specification of the stress tensor in shock wave uniaxial strain experiments. This was not possible in the past. Time-resolved amplitude measurements (particle velocity data) can be used to integrate the governing equations to directly provide longitudinal stress-volume (σ11−V) and shear stress-shear strain (σ12−ε12) relations. No prior assumptions about constitutive response or infinitesimal strain are necessary. Related developments with regards to piezoelectric transducers will be indicated. [Work supported by ONR.]
Generalized viscoelectric models and its electrical analogy
Authors: Tsui Y. T.
Published: October 2005

The stress-strain relations under constant stress or strain are as follows: ε = [1/E′ + t/μ′ + Ψ(t)]σ0H(t). (1) σ = [Eo + μ̄0δ(t) + Ψ̄(t)]ε0H(t). (2) Equations (1) and (2) can be presented by generalized Voigt model and Maxwell model, respectively, which are analogous to two-terminal RC networks. Any two-terminal RC networks can be realized in two canonic forms; one is in series form and other in parallel form. Each form has four basic variations. Starting from Eq. (1): the 1st term corresponds to a single spring of coefficient E′; the 2nd term corresponds to a dashpot of viscosity μ′; Ψ(t) = β ΣiAi(1 − e−1/τi) is creep function, each term of which corresponds to a branch constituted by a spring of modulus Ei and a dashpot of viscosity μ connected in parallel. Since total strain is the sum of all elementary strains, all simple demerits and branches must be connected in series. Thus Eq. (1) is represented by a generalized Voigt model, which corresponds to series canonic form. Considering now Eq. (2): the 1st term corresponds to a single spring of modulus E0; the 2nd to a simple dashpot of viscosity μ̄0; Ψ̄(t) = β̄ ΣiAie1/τ is the stress relaxation function, each term of which corresponds to a branch constituted by a spring of modulus Ē, and a dashpot of viscosity μ̄, connected in series. Since total stress is the sum of all elementary stresses, all simple elements and branches must be connected in parallel. Thus Eq. (2) is associated with a generalized Maxwell model, which corresponds to parallel canonic form.
Surface acoustic admittance and absorption of highly porous, layered, fibrous materials
Authors: Tesar J. S. , Lambert R. F.
Published: October 2005

This study is an experimental investigation of some acoustic properties of Kevlar 29—a fine fibered, layered material. Kevlar is characterized by very high strength, uniform filaments arranged in a parallel batt where must filaments are random in the x-y plane but ordered as planes in the z direction. For experimental purposes, volume porosity, static flow resistance, and mean filament diameter were used to identify the material. These three parameters were carefully measured and then controlled to yield appropriate parameters for the acoustic testing. Only porosities in excess of 89% were used. Of special interest is the use of the Kozeny number to evaluate the static flow resistance. Much of the theoretical work on fibrous porous materials was formulated initially by Zwikker and Kosten, with further refinements by Biot and Lambert in papers published in JASA. Earlier porous material research at the University of Minnesota dealt with highly porous open-cell foams with porosities in excess of 93%. To determine the acoustic surface admittance of Kevlar, batts of the material were cut into small pads and placed into a standing wave tube terminated by a rigid brass plug. At lower frequencies the two-microphone method was used, probing the incident sound field at each frequency in different locations. At higher frequencies the more traditional standing wave method was used to improve accuracy. In both cases, the attenuation and relative phase shift were recorded at each frequency in the range of 50 to 6000 Hz. These propagation parameters were used to determine the surface acoustic admittance of bulk samples and samples of finite depth. Normalized conductance and susceptance were then combined to form the acoustic absorption coefficient. The data are compared with theory by plotting the normalized admittance and normal incident absorption coefficient versus cyclic frequency. [This work was supported by NSF and NASA.]
Dielectric properties of piezoelectric polyvinylidene flouride (PVDF)
Authors: Moffett Mark B. , Powers James M.
Published: October 2005

Measurements were made of the free dielectric constant and the dielectric loss tangent of piezoelectric polyvinylidene fluoride (PVDF) at frequencies between 1 kHz and 5 MHz and temperatures between − 28°C and + 51°C. Samples of nonvoided and voided PVDF were tested. The dielectric constant increases with increasing temperature and/or decreasing frequency, ranging from about 3 to 11 for the voided material and from about 4 to 14 for the nonvoided material. The dielectric loss tangent (dissipation factor) ranged from about 0.02 at low frequencies and high temperatures to about 0.3 at high frequencies and high temperatures. The voided material was not as 1ossy as the nonvoided material, with maximum values 0.2 for the voided material and 0.3 for the nonvoided material. A slight temperature aging effect was observed; an increase of a few percent in dielectric constant resulted from cycling the samples to 51°C.
Complex bulk modulus measurement of fluid-saturated porous aluminum
Authors: Dubbelday Pieter S. , Burns Jay
Published: October 2005

In the application of fluid-saturated porous materials to the absorption of sound it is assumed that the attenuation is enhanced by increased relative velocity between the solid matrix and the fluid. Foamed metals are expected to have a structure that is more rigid than that of other porous materials with larger concomitant absorption. The bulk modulus of such a material was measured in an acoustic coupler filled with castor oil. The viscosity was varied by changing the temperature from 0° to 30°C. Two foamed aluminum samples were used; the first with density relative to that of solid aluminum of 10.1% and 8 pores per cm, the second with relative density of 14.5% and 16 pores per cm. The frequency range was from 100 to 3000 Hz. The pressure was varied from 2 to 20 MPa. The measurements are represented as a complex bulk modulus relative to that of castor oil (assumed lossless), versus the inverse Stokes number, which combines frequency, pore size, and viscosity. The experimental points for the various values of these parameters show satisfactory agreement, and there is a noticeable trend in the variation of real and imaginary parts as a function of the inverse Stokes number. [Work was supported by ONR.]
Adaptive microphone-array system for noise reduction
Authors: Kaneda Yutaka , Ohga Juro
Published: October 2005

A new adaptive microphone-array system for noise reduction (AMNOR system) is introduced. The AMNOR system detects the arrival directions of noise and forms a directional pattern possessing low sensitivities to those directions using a digital filtering technique. With pre-informed data on the direction of desired signal source, the AMNOR system learns the noise arrival directions previously. Optimum filter coefficients are determined based on a new criterion, whose concept is to minimize output noise power while maintaining the degradation in the frequency response to the desired signal below the predetermined value. An algorithm for calculating the optimum filter is proposed. To confirm the effectiveness of the AMNOR system, experiments on the noise reduction processing were carried out in a room with a reverberation time of 0.4 s. A small circular microphone array (radius of 8.5 cm) with four microphone elements and four FIR filters with 16 taps were used. The convergence time of the algorithm at this experimental condition was 0.3 s. Improvement in SNR as a result of the AMNOR system by more than 15 dB in the frequency range of 300–3300 Hz. Superiority over the conventional LMS criterion for noise reduction of speech signals was also confirmed by subjective preference tests.
Shallow sound channels in the North Pacific: Causes, characteristics, and durations
Authors: Dunlap C. R. , Browning D. G. , Powell J. W.
Published: October 2005

There are three principal causes of shallow or secondary sound channels in the North Pacific Ocean: Temperature inversions, water mass intrusions, and dynamic interleaving. Our analysis shows temperature inversions to be widespread throughout the Subarctic North Pacific, water mass intrusions and dynamic interleaving are more associated with specific locations. Examples are given of each type of shallow sound channel, showing their acoustic and oceanographic characteristics. Estimates of the distribution and duration of these channels is given.
The effect of large thermohaline steps on acoustic propagation near the northeast coast of South America
Authors: Chin-Bing Stanley A. , King David B.
Published: October 2005

The acoustical impact on transmission loss due to a thermohaline step profile has been studied using a typical thermohaline step profile taken off the northeast coast of South America in July 1983. Superimposed on the smooth canonical temperature and salinity profiles of the ocean are vertical “fine structure” (1–100 m) perturbations which can affect the acoustic transmission. One mechanism which can cause this “fine structure” is double diffusion (multi-component diffusion) in which each component has a different molecular diffusivity. Under the proper conditions, very dramatic thermohaline steps can occur in which very well mixed regions of 5–200 m thickness are separated by sharp, several meter thick, high gradient interfaces. The impact on the sound velocity profile (SVP) is to create adjacent regions of near isovelocity connected by a high gradient small transition region. Only since the advent of continuous profiling temperature and salinity sensors have these steps been detected; discrete water samples (“bottle casts”) usually did not reveal them. It is seen that transmission loss can be significantly affected even at low frequencies (50 Hz) by failing to include the detailed step structure in the SVP. Furthermore, SVP thinning algorithms using tolerances which seem to preserve the step structure in the SVP can also give erroneous results in the transmission loss.
A simple shallow water propagation model including shear wave effects
Authors: Ellis Dale D. , Chapman D. M. F.
Published: October 2005

The Perkeris model has proved to be very useful in describing some features of acoustic propagation in shallow water, and as a simple test of ideas in normal mode theory. The basic model consists of a homogeneous layer of fluid overlying an infinite homogeneous fluid half-space of greater sound speed. Here we extend the Pekeris model to handle the case of a fluid overlying an elastic basement in which the shear speed is less than the (compressional) speed of sound in the fluid. This gives rise to leaky modes in which both the mode eigenfunctions and eigenvalues are complex. The model predictions are compared to some measured propagation losses for a shallow water site overlying a chalk bottom, where shear-wave conversion at the water-chalk interface causes large losses. The predictions of the simple model explain the very high losses measured at frequencies less than 200 Hz. At higher frequencies the sound speed profile and a thin sediment layer become important, but then an all-fluid normal mode model is in agreement with the measured results.
On the criteria of adiabaticity in coupled mode theory
Authors: Shang E. C.
Published: October 2005

In this paper, it is pointed out that there are two categories of range-dependent waveguide. (1) The range-dependent change of the waveguide is accumulative within the propagation distance, in other words, the space scale of Bmn (r) is much greater than the mode interference distance. (2) The range-dependent change of the waveguide is not accumulated with range, in other words, the space scale of Bmn (r) is much less than the mode interference distance. For the first category, the adiabatic criterion given by Milder is available, but not for the second category. The adiabatic criterion for the second category is modified by using a characteristic distance of Bmn (r) instead of the mode interference distance. The adiabatic criteria for two typical waveguides of the second category (a homogeneous shallow water waveguide with a rough surface and a homogeneous shallow water waveguide with range-dependent sediment type) have been derived. [Work supported by NRC.]
Propagation modelling based on wave field factorization and invariant imbedding
Authors: McCoy John J. , Fishman Louis
Published: October 2005

The proposed propagation models address the propagation of CW acoustic fields through a transition region separating two different, range-independent oceans. Wave field factorization refers to the conceptual decoupling of the radiation fields in the two range-independent oceans, into positive and negative propagating components. Invariant imbedding refers to the reformulation of the propagation problem from a two-point boundary value problem to an initial value problem. In the reformulation the extent of the transition region is an independent variable. The formulation is expressed in terms of reflection and transmission operators, which apply to the transition region. The proposed models are generalizations of existent models in reflection seismology. These latter models allow for no cross-range variability of wave speed in either the two, now homogeneous, oceans nor in the transition region. The seismology models do accommodate P-S coupling, which is neglected in the acoustic application. The incorporation of cross-range variability into existent seismology models or range variability into existent acoustic models are obvious next steps toward models that will address any spatial variability of property fields.
Propagation of sound in fluid wedge overlying a fast bottom
Authors: Sanders James V. , Coppens Alan B. , Kosnik Mark
Published: October 2005

The method of images has been applied to the problems of up-, down-, and cross-slope propagation in a fluid wedge with pressure release upper surface and a bottom consisting of an absorbing fluid with greater density and sound speed. A computer program has been implemented and the properties of the predicted sound field are being studied and compared with results of other approaches and with data from a scaled laboratory model.
Pulsed Scholte wave propagation across periodic and randomly rough liquid/solid interfaces
Authors: Chamuel Jacques R. , Brooke Gary H.
Published: October 2005

Laboratory ultrasonic modeling results are presented showing the effects of periodic and randomly rough liquid/solid interfaces on the transmission of pulsed Scholte waves. For the continuous wave case, it is well known that a stop band exists at the Bragg frequency as indicated by a major dip in the spectrum of the transmitted wave. The new findings reveal that for the pulsed case, the transmitted wave is composed of two parts: a first-arrival attenuated pulse followed by a second late-arrival ringing. The spectrum of the entire transmitted wave train has a major dip at the Bragg frequency. The spectrum of the second late-arrival component alone has a strong peak at the Bragg frequency. These observations indicate that: (a) a substantial amount of energy is transmitted at the Bragg frequency across the periodic interface over a wide time window, and (b) the first-arrival main pulse does not see the distributed feedback (it is not affected by the periodicity of the interface; however, it is simply attenuated by the grooves with no discrimination against a specific frequency). For the randomly rough interface case, destructive interference occurs eliminating the second late-arrival ringing. Other results on the effects of thin parallel rods placed on a flat water/limestone interface are discussed. The findings are related to actual field results from a shallow region of the Canadian Arctic. Studies on the interactions between the Scholte wave and the boundary wave are currently being formulated. [Work supported by DREP.]
Laboratory measurements of mode interaction due to waveguide surface roughness
Authors: Hill Paul D. , Kasputis Stephen R. , Medwin Herman
Published: October 2005

Real ocean waveguides may be strongly influenced by a rough surface bounding the duct. In order to study this scattering problem in its most fundamental form, a rigid-walled, two-dimensional guide with one surface smooth and the other surface either smooth, corrugated, or randomly rough, has been set up in the laboratory. The waveguide is hundreds of depths in extent, is driven by either a “point” source or a mode generating source, and uses either pulse or continuous wave signals. The redistribution of energy among waveguide modes, as a function of the rough surface parameters, is discussed. [Research supported by ONR.]
Incorporating the Burke-Twersky reflection model into the fast field program to predict under-ice transmission loss
Authors: Wales Stephen , Diachok Orest
Published: October 2005

The Burke and Twersky model of reflection from parallel elliptical half-cylinders [J. Acoust. Soc. Am. 40, 883–895 (1966)] has been incorporated into the Fast Field Program and the result used to model under-ice propagation in the Arctic Ocean. Reflection losses as predicted by four forms of the model, closed, series expansion, limited in frequency, and small-angle are discussed for the low-frequency regime. The procedure whereby the model was implemented into the fast field program as a boundary condition is then discussed. At sufficiently low frequencies (below about 30 Hz) where the four expressions yield consistent results, agreement with transmission loss data is excellent. The computed incoherent field follows a dipole pattern, with negligible incoherent energy scattered into the forward direction at small grazing angles. The latter result is consistent with impulse response and horizontal coherence measurements at long ranges and at frequencies below about 40 Hz.
A composite roughness model for underice scattering
Authors: Mellen R. H. , Stocklin P. L. , DiNapoli F. R. , Nielsen R. J. , Deavenport R. L.
Published: October 2005

Underwater sound propagation in the Arctic is characterized by a refractive surface duct with a rough boundary. As the result of scattering, attenuation is some two orders of magnitude greater than medium absorption. Scattering models usually assume statistical homogeneity. We propose a more realistic composite model consisting of spatially random patches having one of two different degrees of roughness. The resulting attenuation coefficient exhibits a relaxation-like transition from rougher to smoother area control as frequency increases. Standard deviations, correlation lengths, and relative areas for the two components are estimated from PDF's and wavenumber spectra of ice-draft profiles. Results are compared with reported attenuation measurements. [Work supported by ONR and NUSC.]
Computer enhancement of education in acoustics
Authors: Holger David K.
Published: October 2005

Computer enhancement of education in acoustics and noise control is discussed. General ideas pertaining to the integration of computers throughout an acoustics program are presented, and various possible levels of computer-based enhancement are suggested. Some ways in which the computer may be used to enhance formal coursework, laboratory instruction, and graduate research in acoustics are discussed. A model for a “fully enhanced” educational program in acoustics that incorporates computer graphics, numerical methods, computer-assisted experimentation, data base management, and word processing is proposed. Specific examples of computer enhancement in an undergraduate lecture/laboratory course and a graduate lecture/laboratory course are presented. Some of the difficulties encountered in developing a partially computer enhanced program in acoustics are discussed.
The use of motion picture computer graphics in acoustics
Authors: Maynard J.D.
Published: October 2005

For some time the Pennsylvania State University has had a program for using computer graphics to produce films for acoustics education. A sample of such a film will be presented in this talk. The original technique for producing these films, involving frame-by-frame exposures, was time consuming. However, we are now using in our research a relatively inexpensive (∼$7000) system which produces complex graphic output moving in real-time. This system, which has a high resolution (2096 × 2096 points), will be described in detail, and, if circumstances permit, will be demonstrated during the talk.
Computer-based experimental modal analysis at Michigan Tech
Authors: Shapton William R. , Wicks Al
Published: October 2005

The computer has applications in nearly every facet of engineering. At Michigan Tech, to complement our CAD/CAM system we have introduced experimental modal analysis to our undergraduate students. The course assumes a background in vibrations and numerical methods, from which we introduce concepts in digital signal processing, and the use of the discrete Fourier transform. The emphasis of this course is to apply numerical techniques to experimental vibrations. Commercially available modal analysis software is used to extract modal parameters from the structures under test. The core of the student experience is a project exploring state-of-the-art concepts in modal analysis. A discussion of the projects and their results is presented. The results of student polling at the conclusion of the course indicated that problems existed in scheduling of computer time, and that project definitions were insufficient for the level of the student. Changes to be made in the course structure include the application of personal computers equipment to the course and the incorporation of a common data base with the on-line CAD/CAM software.
Representation of discrete structure underlying perceptual confusions between phonemes
Authors: Soli Sigfrid D. , Arabic Phipps , Carroll J. Douglas
Published: October 2005

Perceptual processes in speech recognition are generally assumed to be discrete rather than continuous, pointing to the need for general discrete analytic models to represent observed perceptual similarities among speech sounds. The INDCLUS (INdividual Differences CLUStering) model and algorithm [Carroll and Arabic, Psychometrika 48, 157–169 (1983)] can provide this generality, representing symmetric three-way similarity data (conditions × stimuli × stimuli) as an additive combination of overlapping but not necessarily hierarchical clusters whose weights vary as a function of the cluster and condition being considered. INDCLUS was used to obtain a discrete representation of underlying perceptual structure in the Miller and Nicely consonant confusions data [J. Acoust. Soc. Am. 27, 337–352 (1955)]. A 14-cluster solution accounted for 82.9% of the total variance across the 17 listening conditions. The cluster composition and the variation in cluster weights as a function of stimulus degradation were interpreted using the common and unique perceptual attributes of the consonant phonemes within each cluster. Low-pass filtering and noise masking selectively degraded the unique attributes within clusters, while high-pass filtering degraded both unique and common attributes. [Supported by NSF and ONR.]
Intelligibility versus redundancy—A study in Swedish
Authors: Hunnicutt Sheri
Published: October 2005

The relationship between context redundancy and key-word intelligibility was examined in sentences having both high and low redundancy. The study partially replicates work done in 1963 by Philip Lieberman [Language and Speech 6 (Pt 3). 172–187 (1963)] in which he concluded that the degree of stress and carefulness of articulation of a word varies inversely with its redundancy. More words and more extreme redundancies in word pairs were used in the current study. These word pairs were placed in similar positions in two sets of sentences: sentence pairs that one might find in text, and adages together with sentences that might be spoken. With the text-type sentence pairs, there was an intelligibility advantage for the words in lower redundancy contexts. For the adage and spoken-sentence pairs, there was no intelligibility advantage for words in either context. The result that intelligibility and redundancy are inversely related in some instances (text-type sentences), even while reading test sentences, indicates that utterance planning for the speech production mechanism involves interpreting semantic information which may be expressed in fine adjustments in motor control.
Verbal transformations heard with different words at each ear: Consistency of responses upon retest
Authors: Brubaker Brad S. , Warren Richard M.
Published: October 2005

Illusory changes or verbal transformations (VTs), are heard with continued listening to a repeated word. An earlier study of dichotic VTs [Warren and Ackroff, Nature 259, 475–477 (1976)] involving asynchronous delivery of identical repeated words to each ear (interaural delay of one-half the repetition period) found that independent VTs occurred at each ear, and suggested that the identical stimuli at each ear are handled by a separate verbal processor. The present study employed a test/retest procedure using different, rather than identical, repeated words presented simultaneously to each ear. It was found that, while there was a tendency for the same subject to report the same illusory forms for the same repeated words during the second session (a week later) regardless of the ear being stimulated, a higher proportion of forms heard during the first session was also reported during the second when presentation was to the same (rather than the opposite) ear. The implications of these findings for theories of verbal processing will be discussed. [Work supported by NIH and NSF.]
Effects of speaking rate on phonetic perception: Contribution of visual information
Authors: Green Kerry P. , Miller Joanne L.
Published: October 2005

It is by now well-established that the listener makes very precise adjustments for speaking rate when perceiving the phonetic structure of speech. The concern of the present investigation was the nature of the rate information to which the listener adjusts. When a speaker changes rate, he or she alters the timing of articulatory gestures. One consequence is a change in the acoustic form of the speech signal—for example, a change in its overall duration. Such changes provide auditory information about speaking rate. Additionally, however, some of these articulatory gestures are visible on the face of the talker and, therefore, provide visual information about the talker's rate of speech. We asked whether the effective rate information for phonetic perception is limited to the auditory domain or, alternatively, whether visual information about rate from the face also influences the perception of speech. To investigate this question, we paired acoustic versions of /bi/ and /pi/ produced by a talker, at a medium rate of speech, with a video display of the same talker producing these syllables at fast and slow rates of speech. The phenomenal experience that resulted from any given audio-visual pairing was that of a unified percept of a single syllable, produced at a single rate of speech. We found that the variation in the speaking rate of the syllable on the video display (with the rate of the acoustic syllable kept constant) systematically influenced not only the judged rate of the syllable, but also the identification of the syllable as /bi/ or /pi/. These results suggest that at least under some circumstances, auditory and visual information about articulatory timing jointly influence phonetic perception. [Research supported by NIH.]
Lexical analysis for word recognition based on phoneme-pair differences
Authors: Makino Shozo , Wakita Hisashi , Applebaum Ted H.
Published: October 2005

In large vocabulary word recognition systems, it is important to know the phonetic properties of the vocabulary. This paper presents observed phonetic properties of the 5000 most frequent words in the Brown Corpus, and describes a method to evaluate the effects of phoneme recognition errors on word recognition. The study was conducted for two cases: the 5000-word vocabulary with one standard pronunciation per word, and the same vocabulary with multiple pronunciations per word. A distance was defined as the number of different phoneme pairs between two words, taking phoneme deletion and insertion into account. The distance was calculated for every word pair using dynamic programming. Detailed analysis was made of word pairs with distances 0, 1, and 2, and some properties of the vocabulary were obtained which provide useful information in designing a word recognition system. Relations among phoneme recognition score, word recognition score, and vocabulary size were also investigated.
Calculations of monostatic angular distributions for elongated elastic shells
Authors: Green L. H. , Werby M. F.
Published: October 2005

Monostatic angular distributions correspond to measurement of backscattering as one rotates 360° about an object. By such a technique it is possible to ascertain information such as the shape of an object, whether resonances exist, and to observe shell thickness effects. We perform calculations on a number of submerged elastic targets to illustrate these effects.
An application of the spheroidal-coordinate-based transition matrix: Acoustic scattering from high aspect ratio solids
Authors: Hackman Roger H. , Todoroff Douglas G.
Published: October 2005

In a previous paper [R. H. Hackman, J. Acoust. Soc. Am. 75, 35–45 (1984)] a spheroidal-coordinate-based transition matrix formalism was established for acoustic and elastic wave scattering. In this paper, we consider the acoustic scattering by a solid elastic cylinder with hemispherical endcaps and a length-to-diameter ratio of 10. Numerical results are presented for the backscattered form function as a function of frequency for various angles of incidence. These results are compared with experimental measurements taken at the Naval Coastal Systems Center and given a physical interpretation.
Criteria for suitable background choices in resonance acoustic scattering by shells
Authors: Gaunaurd G. , Werby M. F.
Published: October 2005

We present an analytical and computational study of acoustic wave scattering by air-filled spherical/spheroidal shells in water. The calculations displayed here are all performed by means of a recently improved T-matrix approach for shells that is more efficient than usual earlier ones. This study permits the accurate determination of the relative shell thickness at which the usual rigid background of metal shells in water switches to the soft background of gas bubbles in water. The correct choice of background is crucial for the isolation of the shell resonances contained within the echoes. A key criterion to establish this transition thickness, and to decide on the suitability of the background choice, is provided by the relative phase between the (elastic) form function of the target and either the rigid or the soft background. That relative phase will exhibit jumps of π radians as the fluid-loaded system goes through its modal resonances. In the case of an incorrectly chosen background this relative phase will undergo countless meaningless oscillations at all frequencies. Metal shells of the types studied here have transition thicknesses of h/a ≃ 0.001, and the thinner the shells, the narrower their resonances become. These points are all illustrated with examples. We show that soft backgrounds are possible only for shells so thin that they buckle under very light external pressures.
Validation of the Audiometer Telephone Interface (ATI)
Authors: Stoker Richard G. , Donigan Christine , French-St. George Marilyn
Published: October 2005

Speech discrimination scores and connected discourse tracking (CDT) measurements were used to compare the clinical use of the Audiometer Telephone Interface (ATI) [R. G. Stoker, Hear. Instrum. 33(6), 26–29, 46 (1982)] with actual telephone performance on a local telephone company loop. Thirty hearing-impaired subjects from three hearing-loss categories—moderate, sloping; moderate, precipitous; and severe, sloping were used. Subjects were evaluated using standard audiometric procedures (under headphones) and with the ATI (telephone handset with simulated telephone network). Testing was also performed at the subjects' home by providing each subject with an amplifier handset so that the test could be performed at a Most Preferred Listening level (MCL). Stimuli for both the clinical trial and the home trial were the nu-6 word lists and connected discourse tracking using a novel passage with neutral emotional content. Results suggest that the ATI effectively simulates the average hearing difficulty experienced by hearing-impaired telephone users when using their own phones over a local loop served by a variety of central office systems.
Listener recognition of unfamiliar speakers using conversational speech
Authors: Schmidt-Nielsen Astrid
Published: October 2005

Listeners attempted to recognize speakers from short excerpts of conversational speech. The listeners were given two repetitions of a 30-s familiarization paragraph read by each of the five speakers in the recognition set and were told to associate each voice with the name given by the speaker at the beginning of the paragraph. The test consisted of 25 excerpts taken from tape recordings of each of the speakers playing a game of battleship, and the listeners were asked to identify each sample by writing down the name of the speaker. The average duration of the excerpts was slightly more than 2 s. Three sets of five speakers each were tested: one group of female speakers, one group of male speakers who had been rated high in voice distinctiveness (by a separate group of subjects), and one group of male speakers who had been rated low in voice distinctiveness. There were two sets of excerpts for each speaker group, one taken from recordings made while the speakers were conversing over a 2400-bit/s LPC digital voice processor and one made while they were talking over an unprocessed channel. For the more distinctive males and the females, speaker recognition was better over the unprocessed channel than when they were speaking over LPC. However, some of the less distinctive males were better recognized over LPC than over the unprocessed channel, and the others were about the same in both conditions.
Onset effects in lateralization denote a monaural mechanism
Authors: Hafter Ervin R. , Buell Thomas N.
Published: October 2005

Detection of interaural differences of time (IDTs) in trains of high-frequency clicks does not show uniform improvement as a function of the train's length if the interclick interval (ICI) is small; rather, performance is a compressive power function (exponent < 1.0) of ICI, indicating a form of saturation whereby each click reduces the effectiveness of the next. The site of saturation can be studied by intermixing, in a single train, clicks that differ on a dimension known to be encoded in separate neural channels. For example, mixing carrier frequencies finds no interaction between clicks in separate regions, implying that saturation is within frequency channels rather than across them. In the present study, we ask whether saturation is before or after binaural interaction. In both intervals of a two-alternative task, clicks to be lateralized are preceded by clicks with an IDT of 750 μs, leading always to the right. If saturation is binaural, the preceding clicks should not interfere since they address different binaural cells than the test clicks. If the saturation is monaural, the preceding clicks are not differentiated from those which carry information for detection. Results support the latter, showing that saturation occurs in monaural channels feeding the binaural nervous system. [Supported by NIH Grant NS 07787.]
Interaural time discrimination in tonal maskers
Authors: Stern Richard M. , Elsner Ann E. , Schiano Jeffrey L.
Published: October 2005

We have again measured interaural time discrimination performance for 55-dB-SPL 500-Hz tonal targets in the presence of tonal maskers of various frequencies and intensities, with interaural phase angles of 0 and 180 deg. For some masker frequencies we also added a 0–200-Hz noise masker to prevent subjects from using the locations of low-frequency combination tones as perceptual cues. In general, we found that higher-intensity tonal masker at frequencies near that of the target degrade discrimination performance for the targets, and that performance is worse when the target and masker are presented with different interaural phase angles. This dependence of discrimination on the interaural masker phase is more consistent with data obtained in broadband maskers than we had previously reported, and is observed both when target and masker images are perceived separately, and when they are heard as a single fused image. The perceptual cues to perform the task depend on the frequency and intensity of the masker. We will also discuss ways in which these data maybe accounted for in terms of common models of binaural interaction. [Supported by NIH.]
The temporal course of a repulsion effect in auditory lateralization
Authors: Wakefield Gregory H. , Viemeister Neal F.
Published: October 2005

When a dichotic interference is added to a diotic target, the subjective lateral position of the target may be shifted away from that of the interference [R. M. Stern and E. M. Rubinov, “Subjective laterality of noise-masked binaural targets” in Psychophysical, Physiological and Behavioural Studies in Hearing, edited by G. van den Brink and F. A. Bilsen]. The temporal course of this “repulsion” effect was measured using an adaptive procedure in which the apparent position of a probe was varied, by changing its interaural intensity differenc (IID), to estimate the position of the target. The target and interference were independent narrow-band noises centered at 6.3 kHz. The interference was presented for 250 ms with an IID of 12 dB favoring the right ear. The target was presented diotically for 25 ms at the same intensity as the interference in the right ear. As the delay in the onset of the target relative to that of the interference was increased from 0 to 50 ms, the subjective lateral position of the target moved from 2–3 dB to as much as 10 dB favoring the left ear. The target shifted back towards midline, however, for onset delays from 175 to 225 ms (simultaneous offsets). When the target onset occurred at the interference offset, the shift in position rebounded to a value almost as large as that for a 50-ms delay. The shift decayed to less than 1 dB within 200 ms of the interference offset. [Work supported by NINCDS grant NS12125.]
Lateralization of a sound image based on interaural stimulus onset and offset disparity
Authors: Small Arnold M.
Published: October 2005

Sound image location associated with onset or offset disparity was quantified by a scaling procedure in each of three experiments. Steady-state lateralization cues were minimized by using as the stimulus broadband noise which was uncorrelated at each ear. Onset and offset disparity produced lateralization toward the leading and lagging ear, respectively. For a given disparity a greater shift of the sound image in phenomenal space was obtained when the disparity was at onset rather than offset, a finding consistent with earlier work. It has been suggested [G. A. Miller, J. Acoust. Soc. Am. 20, 160–167 (1947)] that offset cues arise from the differential levels of integrated neural activity (loudness) associated with differing duration of the stimuli delivered to each ear. Two tests of this hypothesis were attempted. In one case the potency of a given disparity in producing lateralization was found to be inversely related to stimulus duration, a result in keeping with the hypothesis. However, when equal energy noise bursts appeared at the ears, presumably providing equal levels of neural activity (and loudness), there was no difference in lateralization effect produced by equal energy versus equal-SPL stimuli. The latter results is at odds with the neural activity/loudness suggestion.
Detection and discrimination of auditory motion in the horizontal plane
Authors: Grantham D. Wesley
Published: October 2005

In an anechoic environment subjects discriminated a stationary tone pulse from one that moved left-to-right through a horizontal arc. The moving stimulus was produced by dynamic application of stereophonic balancing algorithms to a two-loudspeaker system with a 30° separation. Distance of loudspeakers from the subject was 1.5 m; all stimuli were 300-ms, 500-Hz tone pulses. A two-interval forced-choice procedure was employed, in which the velocity of the moving stimulus was varied adaptively to track threshold. Average velocity thresholds for four subjects increased from 15°/s for stimuli centered at 0° azimuth to 100°/s for stimuli at ± 90° azimuth. In a second experiment differential velocity thresholds were obtained at 0° azimuth. As the reference velocity increased from 0°/s to 70/s, differential thresholds decreased from about 20°/s to 10°/s. In all cases the minimum audible angle for these subjects were less than or equal to the arc spanned by the moving stimuli at threshold (or the difference between arc spans, in experiment 2). Thus, these data are consistent with the hypothesis that discrimination of auditory motion is based on spatial resolution of stationary (endpoint) auditory events.
Loudness: Independent of the direction of the incident sound
Authors: Theile Günther
Published: October 2005

Up to now it has been accepted that loudness is completely determined by the sound levels at the eardrum. However, recent investigations on spatial hearing indicate that the outer-ear transfer functions, depending on the direction of the incident sound, have no effect on loudness and timbre. Addressing this discussion, a loudness comparison experiment was carried out, using two loudspeakers in an anechoic room. Situation 1: loudspeaker A and B are placed close together in front of the subject. Situation 2: loudspeaker A is placed in front of the subject, loudspeaker B beside the subject, at the same distance as A. In both situations the loudness of loudspeaker B was determined due to the reference loudspeaker A. The matching sound levels in the ear canals were measured using probe microphones. Furthermore, a corresponding loudness comparison test was carried out, using headphones and reproducing the same levels as in the experiment above, which means lateralization instead of localization. The result is: loudness is independent of the position of loudspeaker A and B. It is determined by the sound level of the loudspeakers, but not by the sound levels at the ear drums. The result supports the hypothesis that localization cues cannot be loudness cues. This is predicted by the so-called “association model” in which an adaptive filter with a transfer function inverse to the outer ear transfer function is postulated.
The effect of frequency spectrum on localization
Authors: Lenoble Jill S. , Kubovy Michael
Published: October 2005

The “cocktail party phenomenon” requires that the listener extract the relevant set of frequency components from the complex waveform reaching his ears and group these components into a perceptual unit. We consider two heuristics that might guide this grouping process, grouping based on location and grouping based on harmonicity. Stimuli were constructed such that either all frequency components were in both ears (diotic), half of the components were in each ear (dichotic), or all frequency components were in one ear (monaural). The spacing of frequency components was manipulated using the formula fj = f0Alog2j (Slaymaker, 1970), where j = the component number, A = the ratio of the frequencies of the second to the first component, and f0 = the frequency of the lowest components, for j = 1 to 6. This produces stimuli that sound harmonic for A = 2.00 to A = 2.06. Subjects judged whether the stimuli were presented under monaural, dichotic, or diotic conditions. Subjects tended to report harmonic sounding stimuli as diotic even when they were dichotic, and inharmonic sounding stimuli as dichotic even when they were diotic. Thus, when the stimuli were spectrally fused they were reported as coming from a single location (diotic) and when they were not spectrally fused, the stimuli were reported as coming from two locations (dichotic). This dominance of frequency information over location information is predicted by the theory of indispensable attributes [Kubovy, 1981).
Global feature of wide-band pinna frequency response relating to three-dimensional localization
Authors: Hiranaka Yukio , Yamasaki Hiro
Published: October 2005

We studied the free-field of external ear canal acoustic impulse responses. The fine structure of the frequency domain characteristics was correlated with the time domain profile of the pinna reflections previously [Hiranaka and Yamasaki, J. Acoust. Soc. Am. 73, 291–296 (1983)]. A recent measurement with wide band facilities (up to 50 kHz) revealed the fact that the global structure of the frequency response can be correlated with such effects as the head shadow and the pinna direction in a very simple form: the logarithmic amplitude declines almost linearly with linear frequency for all directions of a sound source, and the degree of the declination varies with the direction. In the experiment, impulsive sound source was positioned at nine elevation angles (30°/step) in each of six vertical planes, and 1.5 m from a subject's head. The directional map of the declination (ranging from − 1 dB/10 kHz to − 10 dB/10 kHz) indicated the opening pattern of the pinna. The patterns of such maps from several subjects showed their physical individuality.