bluuebunny/crossref_metadata_2025 huggingface dataset:
Optional processing strategies in multidimensional discrimination: Integration versus selective attention
Authors: Espinoza-Varas Blas
Published: October 2005

In discrimination of acoustic cues that consist of changes in duration (Δt) and frequency (Δf), listeners can integrate the information from the two dimensions: for any Δf > 0, the just noticeable Δt (d′ = 2.0) can be decreased with Δf, and vice versa [B. Espinoza-Varas, J. Acoust. Soc. Am. 64, S37(A) (1978)]. This paper presents data which suggest that an alternative strategy that listeners can adopt is to selectively attend to one dimension. As in previous reports, the procedure was to measure the IND in t (or f) as a function of Δf (or Δt) in a “same-different” discrimination between pure tones. If the listener selectively attends to Δt, then the just noticeable Δt (d′ = 2.0) remains constant with Δf, except for very large Δf; in addition, for Δt = 0 the value of Δf,d′ = 2.0 is considerably larger than that observed with integration. Analogous effects are observed with attention to Δf. Therefore, degraded resolution for the nonattended dimension would be the main result of selective attention. Integration and selective attention appear as antagonistic strategies: adoption of one tends to preclude the other. Integration occurs preferably when the duration-frequency changes are orthogonally combined, and are matched in discriminability: otherwise, selective attention is more likely. [Supported by NINCDS grant to CID.]
Ultralow frequency discrimination: Can homing pigeons localize infrasounds by Doppler shifts?
Authors: Quine D. B.
Published: October 2005

Homing pigeons detect infrasounds at frequencies as low as 0.05 Hz [M. L. Kreithen and D. B. Quine, J. Comp. Physiol. 129, 1–4 (1979)]. Frequency discrimination at infrasonic frequencies (1, 2, 5, and 10 Hz) is essentially as good as that at “audible” frequencies. Experiments indicate that true frequency discrimination, rather than amplitude discrimination, is being used. Since homing pigeons fly at about 6% the speed of sound, they can produce Doppler shifts in flight of +6%. Pigeons in the laboratory can detect such frequency shifts. A Doppler shift mechanism may provide cues for localization of outdoor infrasonic sources. The interaural differences of intensity and phase probably are too small to use at infrasonic frequencies (wavelengths are tens or thousands of meters). [Work supported by NSF and Cornell Fellowship.]
Are musicians better listeners?
Authors: Spiegel Murray F.
Published: October 2005

An infrequently addressed consideration in psychoacoustics is whether to use musically trained listeners. Two groups of listeners (30 symphony professionals and 30+ nonmusicians) were tested under the same acoustic conditions with a variety of frequency-discrimination tasks (isolated tones and complex patterns). The data reported will bear solely on initial performance levels. The following generalizations are based primarily on this study, but also include the results from training other listeners on the same tasks for longer periods: (a) On simple tasks, small initial differences were observable between music professionals and most nonmusicians. In some cases, nonmusicians were much poorer initially. (b) On complex tasks, the musicians performed better; the overlap between the two groups was much less for the complex task. Musical experience may be beneficial initially for more complicated attentional tasks. (c) Both groups of listeners can have much higher initial thresholds than those obtained from highly trained listeners. Among the advantages musicians bring to auditory tasks are that they may be: innately interested in hearing, more articulate and flexible in their listening strategies, and similar to experienced listeners at the start of an experiment. However, the advantages of musical training are often swamped by the further increase in performance that comes with lengthly training specific to the listening task.
Acoustic reversals of dichotic pitch patterns by musicians and nonmusicians
Authors: DeFosse C. O. , Pinheiro M. L.
Published: October 2005

Normal subjects acoustically reversed a significantly large proportion of responses to monaural pitch patterns. A dichotic approach to this reversal phenomenon might determine its origin. When 20 musicians and 20 nonmusicians were presented with 450 dichotic pairs of pitch pattern triads, the nonmusicians reversed more patterns than the musicians whether report condition was random or right- or left-directed using manual, verbal, or hummed responses. When right and left ears were compared for both the hummed and verbal responses, there were significantly more left ear reversals in the right-directed response and significantly more right ear reversals in the left-directed response. There were no differences between conditions for the manual mode. There were more reversals when the right ear was reported first than when the left ear was reported first and more reversals when the left ear was reported second than when the right ear was reported second. However, there were significantly more reversals for the second reported pattern for all report conditions across response modes. These results indicate that acoustic reversals are probably related to memory decay.
Temporal integration and subjective distortion
Authors: Clack T. D.
Published: October 2005

The amplitudes of inaudible subjective signals are estimated using the monaural tone-on-tone masking procedure. These inferences are based upon three major assumptions: phase-locked generation of subjective signals, vector summation between a subjective and acoustic tone, and the independence of the distortion from the sensitivity processes. Accordingly, any shift in sensitivity without an accompanying change in distortion levels should produce quantifiably predictable variations in the measured phase-amplitude effects. Since the assumptions would most likely be violated at low frequencies, this prediction has been tested with a 250-Hz masker, and comparisons of relatively long- versus short-duration thresholds for a 500-Hz maskee (probe). Observed decreases in phase-magnitude effects with increasing losses in sensitivity follow predictions. These findings: (1) support the validity of the estimation procedure among subjects with normal hearing, (2) suggest a control condition important in estimating subjective tones among abnormal-hearing subjects, and (3) have implications for inferring the origins of the monaural phase effects widely observed with inharmonic and harmonic probe tones of relatively high intensity. [Work supported by NIH and the Department of Otorhinolaryngology, University of Michigan Medical School.]
A new scattering theory for linear random media
Authors: Middleton David
Published: October 2005

A new and canonical approach to scattering problems in linear random media, including interfaces, is described, which incorporates the “classical” continuum theories (Eckart, Tatarskii, Tolstoy, and Clay et al.), the more recent FOM (Faure-Ol'shevskii-Middleton) theory, and the strong-or multiple-scatter interactions (Tatarskii et al.) which can occur in atmospheres and oceans. Random moving media and random interfaces are readily included, as are varieties of different media characteristics, such as radiative and relaxation absorption, random indices of refraction, internal waves, diffusion, etc. Exact (feedback) operational solutions (FOS), where concepts of modern control theory extended to four-dimensional feedback networks are indicated, are here introduced, along with the detailed statistics of the interactive elements in the equivalent FOR (feedback operational representation) and Feynman diagrams and various explicit approximations. The new approach, using generalized random point processes, provides also an anatomy of the scattering elements and their interactions. The general results are illustrated in detail by an explicit calculation of the general covariance of the random moving ocean surface. An example of strong volume interactions is also included. [Work supported by the Office of Naval Research Code 222.]
A ray theory model of acoustic interaction with the ocean bottom
Authors: Lemmon J. J. , Mitchell S. K.
Published: October 2005

Plane-wave reflection coefficients have been computed using ray theory to trace the ray paths in the bottom from an incident plane wave, and then applying the necessary boundary conditions at interfaces by treating each ray locally as a plane wave at the interfaces. In addition to a simple, intuitive picture of bottom interaction, the model affords fast, efficient computations of bottom loss and can be used for signal simulation in the time domain. The primary conclusion of this study is that this “local plane wave” approach works well for realistic models of the ocean bottom down to frequencies of the order of several Hertz. Example results from the model are presented: bottom loss, one-third-octave band averaged bottom loss, the plane-wave impulse response, and simulation of signals generated by explosive sources. The bottom loss results are compared to the results of exact (wave theory) approaches. [Work supported by Naval Ocean Systems Center.]
A plane-wave reflection loss model including sediment rigidity
Authors: Vidmar P. J. , Foreman T. L.
Published: October 2005

A method is presented for calculating the complex plane-wave reflection coefficient of an acoustic wave impinging on an ocean bottom consisting of a continuously stratified solid sediment overlying a semi-infinite homogeneous solid substrate. The depth separated wave equations for the potentials are represented by the “propagator” matrix [F. Gilbert and G. E. Backus, Geophys. 31, 326 (1966).] The method is unique in that the propagator is calculated by direct numerical integration. The reflection coefficient is then accurately computed without recourse to approximation by homogeneous layers or by special functions. The choice of differential equations determines the frequency range for which the method is valid. For gradients typical of marine sediments the Helmholtz equations with depth dependent wave velocities are applicable for frequencies above 10 Hz. Numerical results for a typical turbidite layer for frequencies from 20 to 200 Hz are presented. They show that sediment shear waves can significantly increase the bottom reflection loss for thin (35-m) sediment layers. [Work supported by the Naval Ocean Research and Development Activity and the Naval Electronic Systems Command.]
A numerical simulation of the effects of oceanic finestructure on acoustic transmission
Authors: Ewart Terry E.
Published: October 2005

We present a simple numerical simulation model which includes the effects of oceanic finestructure together with previously developed theoretical treatments of the effects of internal waves on acoustic transmission. We combine the wave equation solution to particular layer geometries developed by Brekhovskikh with the theoretical model of acoustic scattering based on internal waves developed by Desaubies. In our model we assume that the finestructure layers are passively advected by internal waves and that the effects of the layers modulates the effects of internal waves. Experiments carried out at Cobb Seamount over a fixed, horizontal, wholly refracted path indicate that the power spectrum of the phase fluctuations is fit nearly exactly by models based on internal waves only, while the power spectrum of the log amplitude fluctuations is not. For our treatment the predictions of the phase fluctuations remain unaffected by the presence of finestructure and the predicted power spectrum of the log amplitude is in considerably better agreement with observation.
Development of a noise test procedure for vacuum cleaners
Authors: Mansbach Peter A.
Published: October 2005

A simple test procedure for determining A-weighted sound power emission from household vacuum cleaners was systematically developed. Representative units were tested in various configurations and on different carpets to determine the sensitivity of noise emission to various operational factors. With a single configuration selected, these units were then tested in various acoustic environments, using direct and comparison methods, to evaluate the effects of the test environment. Tests were also run with fewer microphones. Concurrently, human response tests were conducted to determine whether a pure tone correction was indicated. An analysis of modal overlap in relation to tonal content was undertaken, and several existing standards were reviewed. The resulting test procedure is a comparison sound power measurement, using four microphones in a “semi-reverberant” room similar to the ISO 3743 “special test room,” but less restrictive. A round robin conducted using this procedure has indicated a measurement precision of about 1 dB.
A survey of communications in the high noise environment of Army aircraft
Authors: Mayer Mitchell S. , Lindberg Arthur W.
Published: October 2005

In Army aircraft, the noise environment consists of a continuous noise level comprised of a mixture of random (broadband) and periodic frequencies (the aircraft noise signature or “whine”) and in the case of gunships, transient high-level noise bursts generated by the weapons systems. The noise environment reaching the aviator's ear is comprised of direct ambient noise penetration and communications systems processed noise (during periods of communications use, or “open mike operations”). The most insidious impact of the high noise levels is the long-term permanent hearing threshold shift, or hearing loss, that the aviator may incur from his prolonged exposure to the aircraft's interior sound pressure levels. Improvement of speech intelligibility under all flight conditions will improve the aviator's effectiveness by reducing the number of transmission repetitions necessary to assure that a message is correctly conveyed, thus reducing the distraction level during critical mission phases. Reducing the ambient aircraft noise processed by the communications system will further improve speech intelligibility and reduce this particular increased noise contribution to pilot stress.
Fourier analysis in the laboratory
Authors: Rossing Thomas D.
Published: October 2005

Spectral analysis of complex waveforms is the basis of many instructive demonstration and laboratory experiments in teaching acoustics and wave motion. Fourier analysis may employ either digital or analog techniques. Digital techniques, such as the fast Fourier transform algorithm, are easily carried out on hand calculators, and there are a number of real-time spectrum analyzers which make use of these methods. Analog techniques include the use of multiple filters, a swept-frequency filter, or a heterodyne arrangement. Limitations on the sweep rate of a filter can be circumvented by employing the time-compression technique. These various techniques for Fourier analysis will be compared and a number of analyzers costing from $38 to $20 000 will be described and demonstrated.
Concerning the ultrasonic Doppler flowmeter
Authors: Rey T.
Published: October 2005

The ultrasonic Doppler flowmeter is used in medical diagnosis and research to indicate velocity of blood in a vessel to which transducers are coupled externally. In this note, the observed frequency shift is shown to be proportional to the magnitude of the acceleration of the blood flow, rather than its velocity.
New digital acoustic signal processing for use in ultrasonic intrusion alarm systems
Authors: Massa Donald P.
Published: October 2005

It has been the accepted belief that air turbulence in an ultrasonic alarm system produces a Doppler shift similar to that produced by a moving target, resulting in false alarms. A mathematical analysis of the entire acoustic system shows that this assumption is not true. It is shown that the received ultrasonic signal can be represented by a rotating phasor whose head exhibits circular motion when a moving target is present. The circular motion is virtually non-existent when a moving target is absent regardless of the presence of environmental disturbances, such as air turbulence and noise transients. The mathematical findings have been confirmed experimentally. An electronic circle detector incorporating a microprocessor was developed for recognizing the presence of circular motion in the head of a rotating phasor when it occurs in the received signal. This permits the system to absolutely detect a moving target while remaining immune to false alarms due to air turbulence and other environmental disturbances. This microprocessor-based digital signal processing also totally eliminates the need for any sensitivity controls as are required by all prior art systems.
Location of the nitrogen vibrational relaxation peak μmax on frequency/pressure (f/p) axis as a function of humidity in N2-H2O gas mixtures
Authors: Griffin W. A. , Zuckerwar A. J.
Published: October 2005

The free-decay technique was employed in a resonance tube to obtain nine sets of sound absorption data in N2-H2O gas mixtures and requisite companion data in pure N2 and N2-CO2 gas mixtures. N2-H2O gas mixture pressures ranged from 1–80.5 arm, water vapor content ranged from ∼57 to 14500 ppm (0.0057% to 1.45%), and the f/p range was 0.1–1000 Hz/atm. All measurements were made at ambient temperature of 297°K. Preliminary results show that the nitrogen vibrational relaxation peak is shifted on the f/p axis according to the following relation: (f/p)R − a0 + a1h; where a1 = 221 h. h = mole % H2O at 297°K, and a0 < 0.06 Hz/atm. [Work supported by NASA Grant NSG-1324.]
The effect of impurity gases on molecular absorption using an acoustic resonant technique
Authors: Lee M. C. , Barmatz M. , Frazer R. E.
Published: October 2005

A high precision cylindrical resonator has been employed to study the effects of impurity gases on the molecular absorption in oxygen. The resonator is capable of handling temperatures up to 500°C and pressures up to 100 atmospheres covering an effective f/p range from 10 to 250 000 Hz/atm. The effects of He4 and CO2 gases on the molecular absorption in oxygen within these experimental regions will be presented and compared with previous measurement using other techniques, such as the direct absorption method [Bass, J. Chem. Physics, 58, 4783 (1973)] and shock interferometry [Millikan and White, J. Chem. Phys. 39, 3209 (1963)]. [Work supported by NASA.]
Propagation of sound waves in water fogs
Authors: Rong-jue Wei , Wei Y. T.
Published: October 2005

The present report tends to summarize progress of the propagation of sound in foggy air since 1940s, with emphasis on the relaxation absorption and dispersion induced by mass transfer of fog droplets. Both theory and experiment in this report will be discussed in some details.
Computerized ultrasonic characterization of ocular tissues
Authors: Lizzi F. L. , Feleppa E. , Herbst J. , Jaremko N. , Coleman D. J.
Published: October 2005

Ultrasonic characterization, using digital techniques, is being applied to clinical data gathered in examination of the eye and orbit. Digital rf echo signals are obtained from structures situated within a 7.5 × 20 mm region of the eye. A dedicated minicomputer system is employed to select specific portions of these records for analysis. Using a simple instruction set, a variety of analysis techniques can be chosen to characterize specific types of structures. For example, small ocular tumors are examined with spectrum analysis techniques to delineate surface features, internal scattering characteristics, and shadowing of posterior scatterers such as orbital fat elements. The use of analysis procedures is guided by the display of reconstructed, gray-scale B-scans. Computational results are presented in a variety of display formats (including color-coded and isometric modes) to facilitate recognition of fundamental tissue features. Data are catalogued for continuing evaluation of tissue characteristics that are useful for diagnostic purposes and for refinement of mathematical modeling based on histological preparations resulting from surgery. [Work supported by the NIH.]
Nonlinear acoustic behavior in focused ultrasonic fields: Propagation in water and biological tissue
Authors: Goss S. A. , Fry F. J.
Published: October 2005

Nonlinear acoustic behavior in the form of harmonic generation is observed within the focal region of a focused ultrasonic field in degassed distilled water as well as in biological tissue. The observations were made using a miniature hydrophone probe whose frequency response has been characterized. The phenomena was also observed in nonlinear absorption measurements in biological tissues using the transient thermoelectric technique. Harmonic generation appears to be of significance at spatial peak intensities greater than about 60 W/cm2 in the media studied here. While harmonic generation itself appears to be confined to the focal region of the beam, the harmonics are seen to propagate well beyond the focus. The implications of this phenomena with respect to the application of high-intensity ultrasonic fields used in medicine and biology are discussed. [Work supported by NINCDS and NIH.]
Applications of recent work on design criteria for ensemble in arena concert halls
Authors: Marshall A. H. , Hyde J. R.
Published: October 2005

Recent work which established the acoustical conditions for ease of ensemble on stage [A. H. Marshall, D. Gottlob, and H. Alrutz. J. Acoust. Soc. Am. 64, 1437–1442 (1978)] has been applied in two designs for arena stages. The first design has been constructed in the existing Christchurch Town Hall [A. H. Marshall, J. Acoust. Soc. Am. 65, 951 (1979)]. A set of surfaces based on the reported work was installed above and around the stage in May 1978. At the first concert following, critics noted the excellence of ensemble playing and a questionnaire to the orchestra, which previously had expressed some difficulty with ensemble, elicited an overwhelmingly favorable response. The second part of the paper reports progress on the design of the stage and “ensemble” surfaces in the Wellington Town Hall. General conclusions about the design of arena stages for orchestral use are drawn.
Stochastic process modeling of sound energy decay in rooms
Authors: Walsh John P.
Published: October 2005

The discrete parameter first order Markov chain model of the reverberation process developed at Göttingen has, as a limitation, an inability to deal with unequal free path lengths. A continuous parameter Markov chain model has been developed which eliminates this difficulty, but which yields results which are much worse predictors of the reverberation characteristics of the scale model room tested at Göttingen. The success of the discrete parameter model has been found to be a beneficial, but erroneous, result of the equal free path assumption. The overall failure of the Markov Model was traced to its “memorylessness” property, which in effect forces all reflections to diffuse. In the two rooms investigated, specular reflections predominate, and so the assumption implied by the use of the first order Markov model was manifested in its poor predicting power. A more general stochastic process model is proposed which permits the use of a mixture of low-order and high-order terms to describe, respectively, scattering and specular reflection. This model may be considered a multivariate digital filter, since, as formulated here, it operates in discrete time, but without encountering the problems noted for the Göttingen discrete parameter Markov model. In addition to having the potential for far superior predicting power, it should also present fewer computational problems than multiple order Markov chains.
Experimental evaluation of scattering surfaces for concert hall applications
Authors: Walsh John P. , Bradley John S.
Published: October 2005

To evaluate the relative merits of scattering surfaces which might be incorporated in concert hall construction, the two-dimensional polar responses for several model panels were determined. The panels, which included a quarter cylinder, a wedge, and maximum-length and quadratic residue sequences, were judged on the basis of both the intensity of the scattered energy and the uniformity of scattering in a half-plane. To enable this to be done, the levels relative to the incident SPL were determined at increments of π/16 radians; the sample means and standard deviations of this data served as quantifiers of the intensity and uniformity criteria. Examination of these statistics versus frequency (λ < l < 8λ, l = panel dimension) with regard to the subjective effects of attenuated early reflections provided a basis from which to determine the suitability of each design. A result of some interest is that multiple-period maximum-length and quadratic residue sequences exhibited interperiod interference effects which might be found problematic in architectural applications.
Acoustical support for small performing groups in “surround” concert halls
Authors: Schultz Theodore J.
Published: October 2005

When a small musical group, such as a string quartet, performs on a large stage, it is usually placed downstage center, in order to achieve close contact with the audience. In this location there are no nearby sound reflecting surfaces to give acoustical support. If the audience is seated “out in front,” as in a proscenium theater the musicians can be helped by surrounding them at the sides and rear with a temporary folding screen, to provide close-in sound reflections and reinforcement of their music. At the same time, it provides a suitable visual background to prevent their appearing lost on the large stage. So long as the height of the screen exceeds about six feet, the acoustical requirements are satisfied and the exact height is a matter only of visual concern. However, when the audience surrounds the stage, as in a number of new concert and recital halls, this approach does not work because the musicians are hidded from view for the audience around the stage. This paper discusses a recital screen for use in surround halls whose height is very much less than is customary. Examples are presented and the acoustical performance is discussed.
Mechanics Hall, Worcester, Massachusetts: An historical restoration
Authors: Cavanaugh W. J. , Kaye D. H.
Published: October 2005

Worcester County's version of the burgeoning 19th century New England “Mechanics Associations” started in 1842 and a few years later ground was broken for the building which would house the association's fairs, trade shows, lectures, concerts, and other cultural events. A local architect, Elbridge Boyden, was paid $500 to design the “Victorian” structure in downtown Worcester, which was to house an “acoustically perfect” 1500 seat hall on the third level, a 600 seat hall directly below on the second level and the more profiitable shops and other rental space at the street level. Thoreau, Mark Twain, and Dickens spoke in the hall and Caruso, Paderewski, among others, made music. In the 20th century, the building, like most in downtown urban centers, fell into decline, being ultimately used for roller skating. In 1974, the Mechanics Hall Association acquired funding to renovate the hall under the guidance of Anderson Notter Finegold Associates of Boston. In November 1977 the opening concert initiated a varied and successful new life for this classical hall. The acoustical design challenges of this restoration are described, including details of the sound reinforcement system and its unique three way loudspeaker cluster design.
A statistical analysis of audience sound absorption
Authors: Ramakrishna B. S.
Published: October 2005

The absorption produced by the audience in concert halls is considered a random variable. Beranek's proposal [L. L. Beranek, Music, Acoustics and Architecture (Wiley, New York, 1962), p. 543] that audience absorption is proportional to the area they occupy and not to their number is subjected to a statistical hypothesis test. A two variable linear regression model of the absorption with audience area and residual area as regressor variables is postulated for concert halls without added absorptive materials. Since Beranek's contention amounts to the statement that audience absorption is independent of the seating density, the test of the hypothesis lies in categorizing halls by seating density and examining for significant differences among slopes of regression planes of the different categories. Such a test shows that Beranek's hypothesis can be accepted. It is also shown that the audience area is a better predictor of the absorption than the audience number. The absorption coefficients and their 95% confidence limits are given for the audience and residual areas. A critique of the regression model is presented.
Computer studies of reverberant sound fields in rectangular rooms: Eigenmode model
Authors: Chu W. T.
Published: October 2005

Recent successes in bringing together the eigenmode and free-wave models of reverberant sound fields in rectangular rooms depends on the high-frequency limit assumption which permits the summation of discrete modes to be changed to a continuous integration over the wavenumber space. To render stronger support for this reconciliation, it is felt that a computer study using discrete summation of the allowable modes would be instructive. Such a study was carried out with a minicomputer. Computed results of the sampling statistics, the spatial cross-correlation functions and the interference patterns near boundaries are in good agreement with predictions based on the free-wave mode. The distinction between pure-tone and random-noise excitations in relation to the quantities being studied has been confirmed to be important and necessary.
The transmission loss of a wall incorporating an array of resonators
Authors: Garrelick Joel M.
Published: October 2005

Resonators, and in particular Helmholtz resonators, are often used to enhance the reflection loss of a given surface. In this paper, the associated effect on transmission loss is analyzed. The mathematical model consists of a rigid moveable wall of infinite extent and molded to form slotted cavities which create an array of line resonators. The pressure within each cavity is governed by the wave equation and the wall motion is assumed to be proportional to the net pressure on the wall surfaces. In response to a normally incident plane wave, the transmitted pressure is determined and numerical results are presented for various configurations. It is shown that the resonator array can significantly enhance the transmission loss of the wall. The effects of slot width, wall mass and the cascading of cavities of differing dimensions are discussed.
Review of imaging of sound fields
Authors: Bucaro J. A.
Published: October 2005

The fact that optical beams can probe acoustic fields in transparent elastic media in a nonobtrusive manner has led over the years to the development of a variety of acousto-optic visualization techniques. The ability to “see” the sound field distribution provides a great advantage in experimental studies of acoustic phenomena as well as in evaluation of acoustic devices. This paper will review the basic approaches to the visualization of acoustic fields by means of optical beams. Some emphasis will be given in the discussion to the use of such to obtain “quantitative” views of the acoustic field.
Side-scan sonar and its relation to holography
Authors: Kock Winston E.
Published: October 2005

Side-scan sonar is the equivalent of synthetic-aperture radar, a University of Michigan development in the 1950's. Then classified, it was first described in the open literature in 1966 in communication theory terms. The similarity of the synthetic aperture technique to holography was pointed out by the author in 1967, and a 1968 paper co-authored by laser holography pioneer Emmett Leith (a co-author of the 1966 synthetic aperture paper) noted that “the holographic viewpoint has led to designs which are not easily explicable from the communication theory viewpoint.” Because radar and sonar are both echo-location systems, papers on the use of synthetic aperture concepts in sonar began appearing in 1968, including a 1974 paper describing synthetic-aperture B-scan sonar techniques in medical applications, and a 1970 U.S. patent on synthetic-aperture ultrasonic imaging techniques. The present paper reviews the side-scan principles, its recent advances and applications and briefly describes the possibilities of holographic space-frequency equivalence [W. E. Kock, International Optical Computing Conference (I.O.C.C. 78), London, England, September 6, 1978] in side-scan sonar. [Work supported by the Herman Schneider Laboratory.]
New results in ultrasonic microscopy
Authors: Quate C. F.
Published: October 2005

The mechanically scanned microscope using acoustic radiation in water near 3 GHz has a resolution comparable to the optical microscope and the details that appear in the optical micrograph now appear in the acoustic micrographs. In addition it is now possible to probe some of the subsurface detail on objects—en;such as metallic layers—that are opaque to optical waves. This feature suggests that the acoustic microscope may have a unique role in the continuing exploration of the microscopic world. With biological samples acoustic microscopy permits one to record images with large contrast in unstained cells. In this talk we will discuss the latest work in this field. We will include images from an instrument immersed in a cryogenic fluid (liquid argon). There the wavelength is now 4000 Å with great hope for much shorter wavelengths in future microscopes. [Work supported by AFOSR and ONR.]
Contralateral-probe measurements of auditory vowel spectra
Authors: Sachs R. M. , Zurek P. M.
Published: October 2005

Four steady-state vowels/i, u, a, ɛ/ were synthesized with Peterson and Barney's [J. Acoust. Soc. Am. 24 (1952)] average male formant frequencies. A contralateral probe tone was set at each harmonic covering the frequency range of the first three formants of each vowel. Listeners adjusted, independently, the amplitude and (below 1400 Hz) the phase of the probe tone to center the tonal image. The resulting plots of probe adjustments versus frequency are interpreted as the internal representations of vowel spectra. The most consistent and striking characteristic of these spectra is the enhancement, relative to the physical spectra, of the peak-to-valley differences in amplitudes of harmonics: i.e., the internal formants are sharper than the physical ones. A comparison of these vowel measurements with measurements of simpler two- and three-tone stimuli leads us to attribute the sharpening of vowel formants to the suppressive action of a small subset of nearby harmonics. [Work supported by NINCDS Grant NS03856.]
The temporal course of suppression as measured in a lateralization procedure
Authors: Kearney J. K.
Published: October 2005

A lateralization procedure [T. Houtgast, Acustica 30, 214-221 (1974); W. Jesteadt and E. Javel, J. Acoust. Soc. Am. 63, S44(A) (1978)] was used to measure the suppression of a monaural 500-msec, bandpass noise on a 15-ms tone as a function of the temporal relationship between the suppressor and the tone. Suppression was estimated by presenting the brief tone binaurally and adjusting its level in the contralateral ear in order to produce a centered image. Inferences from pulsation-threshold and unmasking experiments have led to the belief that suppression must have very short (even instantaneous) rise and decay times, but this simultaneous procedure indicates that the rise and decay have markedly different time courses—at the onset of the suppressor, suppression increases rapidly, but it decays relatively slowly at suppressor offset. Using the same stimuli and subjects, the time course of masking was also measured and the data will be compared with the suppression data. [Work supported by NINCDS.]
Two-tone suppression in forward masking as a function of probe frequency and suppressor frequency
Authors: Moore Brian C. J.
Published: October 2005

Masking functions (probe threshold vs probe frequency) in forward masking were measured for a tonal masker at 2 kHz with and without a suppressing tone. An adaptive 2IFC procedure was used with 300-ms maskers (10 ms rise/fall), 20-ms probe tones (10 ms rise/fall, no steady state), and no silent interval between masker and probe. The frequency of the suppressing tone was varied in the range 2025 to 2800 Hz. The suppression, measured as the reduction in probe threshold produced by adding the suppressing tone, was found to have two components. One component was limited to a narrow range of probe frequencies around 2 kHz, while the other component shifted in frequency region as the frequency of the suppressing tone was altered. In some cases there were two distinct peaks in the functions relating amount of suppression to probe frequency. The suppression around 2 kHz probably reflects a qualitative change in the cues available to the observer when a suppressing tone is added to the masker, while the suppression which shifts with the frequency of the suppressor may reflect a reduction in level of only part of the excitation pattern of the masking tone.
Masker interaction in pure-tone forward masking
Authors: Width Gregory P. , Viemeister Neal F.
Published: October 2005

Forward masking of a 1-kHz, 20-ms probe was examined using two temporally distinct 1-kHz, 20-ms maskers, separated by 6.5 ms. The interval between the second masker and the probe was the same as the interval between the first and second masker. Masking functions were obtained for each masker separately, and for varying levels of the second masker with a fixed level (90 dB SPL) of the first. In general, the presence of the first masker at a fixed level raises the probe threshold by a constant amount over that for the second masker alone. Masking (dB) for the combined maskers is less than the dB-sum of masking, but in general exceeds the intensity-sum of masking, as determined for each of the maskers separately. The results indicate that both maskers affect the detectability of the probe, and that the first masker reduces the effective level of the second masker, perhaps by simple attenuation. [Research supported by Sigma Xi, NINCDS, NICHD, NSF, and the Graduate School of the University of Minnesota.]
Phase sensitivity and forward and backward masking using transients
Authors: Gaskell H.
Published: October 2005

The detectability of a probe signal is reduced if it is followed, after a short delay, by a masking stimulus: this phenomenon is known as backward masking. Similarly, in forward masking, probe detectability is reduced by a preceding masker. 20-μs rectangular pulses presented diotically over TDH-39 earphones were used as both probe and masking stimuli in a two-interval forced-choice detection procedure. The masker was always presented at 30 dB sensation level, and, for a given probe-masker delay, the amplitude of the probe was varied to obtain a psychometric function. Delays from zero to 4 ms were used. In both forward and backward masking, as the delay was increased from zero, the amplitude of the probe necessary for 75% correct detection increased to a maximum at a delay of 400 μs and then decreased to zero masking at 4 ms. Further, observers were able to discriminate the temporal order of two pulses of unequal amplitude when the delay between them was as small as 200 μs. [This research was supported by the Science Research Council.]
A forced-choice paradigm for pulsation-threshold measurements
Authors: DuMond Gregory J. , Stern Richard M.
Published: October 2005

A 2I-2AFC paradigm for pulsation-threshold measurements is described and compared to the conventional method of adjustment. A pulsation-threshold stimulus consisting of four bursts of a masker in rapid temporal alternation with three bursts of a target was presented during one interval of each trial in the forced-choice experiments. The stimulus in the other interval was similar, except that the target remained on during the second and third masker bursts. As target-to-masker ratio decreased the pulsed targets sounded more continuous, and became difficult to discriminate from the continuously presented targets. Pulsation thresholds were measured using various monaural and binaural targets and maskers. The difference between thresholds obtained using the forced-choice and adjustment procedures depended on whether tonal or broadband maskers were used. However, the dependence of these thresholds on masker parameters such as frequency, intensity, and interaural phase were similar for the two procedures. It appears that variability in pulsation thresholds due to subjective criterion fluctuations using the method of adjustment can be eliminated by use of the forced-choice paradigm. [Supported by NIH.]
Effective masking bandwidths at low frequencies
Authors: Fidell S. , Horonjeff R. , Green D.
Published: October 2005

Determinations of effective masking bandwidths at low frequencies are scarce because of inherent difficulties in such experimentation, including needs for very high signal levels and very quiet listening conditions. The current experimentation was undertaken to estimate signal to noise ratios associated with three levels of detection performance in a two alternative forced choice task at six frequencies between 40 and 1000 Hz. Both signals and noise backgrounds were presented to observers by loudspeaker in an anechoic chamber. Effective masking bandwidths (inferred by the critical ratio method) were observed to decrease from 1000 to 250 Hz, and then to increase substantially at lower frequencies. [Research sponsored by the Applied Technology Laboratory, U.S. Army Aviation Research and Development Command.]
Pure-tone masking in the parakeet: The effects of a constant masker SPL on probe-tone threshold
Authors: Saunders James C. , Pallone Robert L.
Published: October 2005

Four parakeets were trained to make an avoidance response in the presence of pure-tone stimuli. When this behavior was well established a method of limits was introduced and thresholds in the quiet were measured at test frequencies between 0.2 and 8.0 kHz. A masking procedure was then introduced and the masked thresholds for probe tones at 0.63, 1.0, 1.6, 2.5, 3.5, and 5.0 kHz were measured. Masked thresholds were obtained at 5 or 7 masker frequencies about each probe tone. The SPL was kept constant for each set of masker frequencies and masking curves were further obtained at a variety of masker sensation levels between 20 and 80 dB. The masking curves were generally parallel to each other as the sensation level changed and at the highest masker level the curves did not exhibit the spread of masking found in equivalent mammalian data. The frequency selectivity of the masking curves also changed systematically as higher probe-tone frequencies were tested. The procedure may provide a psychophysical analogue of the “response area curve.” [Work supported by NSF.]
Detection of amplitude modulation
Authors: Hartmann W. M.
Published: October 2005

The detection of frequency modulation at high modulation frequencies seems to be based upon detection of the first lower modulation sideband in the presence of the carrier as masker. This conclusion followed from a series of interleaved experiments on modulation detection and sine tone masking. [W. M. Hartmann, J. Acoust. Soc. Am. 63, S66(A) (1978)]. The present paper reports a similar combined study of amplitude modulation detection and masking. The AM detection experiment used an 80 dB. 1000 Hz carrier with high and low modulation frequencies. The masking experiment used an 80 dB, 1000 Hz masker and a target tone with frequency equal to a sideband frequency from the AM experiment. Each experimental run consisted of an AM detection half and a masking half. Both halves employed a 2IFC staircase method. The results for three subjects show that for modulation frequencies of 200, 150, and 100 Hz, AM detection threshold occurs when the lower modulation sideband is at masked threshold. For modulation frequencies of 50, 25, and 12 Hz, AM is detected when the lower sideband is 5.2 dB (±1.3 dB) below masked threshold. These results agree with a duplex model of AM detection. In this model AM detection is based upon lower sideband detection for high modulation frequencies and upon detection of intensity fluctuations for low modulation frequencies. [Supported by the NSF.]
Detection of sinusoidally amplitude modulated noise by chinchillas
Authors: Salvi R. , Giraudi D. , Henderson D. , Hamernik R.
Published: October 2005

The amplitude modulation threshold for sinusoidally modulated noise was measured in chinchillas using stock avoidance conditioning procedures. Chinchillas were initially conditioned to respond to noise bursts and their thresholds for the noise bursts were measured. Then, the chinchillas were conditioned to respond to amplitude modulations in a continuous noise. The modulation frequencies were between 2 and 2048 Hz. The modulation thresholds were approximately 9%– 10% at modulation frequencies below 16 Hz. At higher modulation frequencies, the threshold increased and approached a limiting value of approximately 40%-50% near 1 kHz. Modulation thresholds were also measured in human listeners using the same experimental apparatus. The thresholds for humans were lower than those for the chinchilla at modulation frequencies below 64 Hz. [Supported in part by NSF, NIOSH, NIEHS.]
Effect of focused ultrasound on thin membranes within the eye
Authors: Lizzi F. L. , El-Mofty A. A. , Driller J. , Franzen L. , Coleman D. J.
Published: October 2005

An experimental program, utilizing over 50 rabbits, evaluated the use of focused ultrasound to cause accelerated resorption of vitreous membranes. Membranes were formed in the vitreous of the anesthetized rabbit eye by injection of 0.1 ml of platelet-rich plasma. Membranes formed in the vitreous produced sequelae similar to those produced by membranes seen clinically. Membranes were insonified with multiple, 5-s duration exposures of focused ultrasound at 9.8 MHz. Insonified membranes resorbed at a significantly accelerated rate when compared to uninsonified membranes (controls and shams). Pulsed insonification at 10 Hz pulse repetition rate was found to be most effective. Careful positioning of the focused beam on the membrane enhanced effectiveness of low intensities and reduced unwanted effects on adjacent normal tissue structures. [Work supported by the NIH.]
Auditory modeling of vowels
Authors: Bladon R. A. W. , Lindblom Björn
Published: October 2005

In order to shed light on a specific theory of peripheral auditory representation (drawn from work by Zwicker and recently formalized by Schroeder, Atal, and Hall) we have used data on how listeners match two-formant vowels to four-formant stimuli. We report on two experiments designed to test the hypothesis that such listeners determined their favored F2′ according to a distance measure (adapted from Plomp) formulated in terms of such auditory representations. This theory models the auditory transformation of the acoustic signal as a conversion of the power spectrum into a sones/Bark representation by computing critical-band densities and applying a (basilar membrane-like) frequency smearing function. The computed pseudoauditory vowel distance measure was found to correlate very highly with the listeners judgments of vowel-quality distance obtained from the two experiments described, which involved the comparison of numerous vowel pairs from reported F2′ data. The results suggest that a model of peripheral auditory representation is available which would be useful as a building block in any theory of speech perception.