bluuebunny/crossref_metadata_2025 huggingface dataset:
The Acoustic Field in a Homogeneous Solid Sphere Excited by an Incident Wave in the Ambient Fluid
Authors: Feldman Henry R.
Published: October 2005

Further computations of the acoustic field in a solid elastic sphere have been carried out, using the solution to the wave equation boundary-value problem for an incident monochromatic wave. Previous computations have been extended to include the observation of transverse as well as the radial stress in the elastic medium. Special attention has been given to regions of focus (in the geometric limit) for both dilational and shear mode propagation. The results are of interest in analyzing the behavior of wide-angle underwater acoustic lenses.
Computer Simulation of the Cochlear Potentials
Authors: Laszlo Charles A.
Published: October 2005

The relation between the microscopic potential generators in the organ of Corti and the macroscopic measurements of the CM and SP by differential electrodes was investigated using computer simulation of the dynamic processes in the ear. The computer simulation was based on mathematical models that take into account the appropriate low-pass filter characteristics of the middle ear, the unique behavior of the basilar membrane, the mechanical structure of the organ of Corti, and the spatial distribution of hair cells in the cochlea. Using this technique, we investigated: (1) the nonlinearity of the transduction process and the waveform of the macroscopically measured cochlear potential, (2) the effect of the value of attenuation changes of the perilymph and tissues on the differentially measured potentials, (3) the behavior of the CM and the SP as a function of sound-pressure level, and (4) this behavior as a function of frequency. The results of this simulation are compatible with experimental observations and further substantiate the essence of the concepts of Whitfield and Ross [J. Acoust. Soc. Amer. 38, 126–131 (1965)], although not all its details. This approach also provides clues to the nature of the nonlinearities of the mechanoelectrical transduction process in the inner ear.
Axially Symmetric Torsional Waves in Circular Composite Cylinders
Authors: Haines D. W. , Lee P. C. Y.
Published: October 2005

A method is developed to obtain the dispersion diagram for axially symmetric torsional waves in any type of elastic circular cylinder composed of a core perfectly bonded to an outer casing. The method is based on the application of two sets of bounds that are easily obtained. One set represents solutions of a solid cylinder with geometric and material properties identical with the core; the other set of bounds represents solutions of a hollow cylinder with its properties identical with the casing. Certain intersections of the two sets of bounds correspond to solutions of the frequency equation of the composite cylinder. Therefore the frequency branches weave through these intersections, but otherwise stay between the bounds. The dispersion diagram of the composite cylinder is thus obtained. Both real and imaginary wavenumbers occur. Other complex wavenumbers are shown not to exist.
Noise and Vibration of Resiliently Supported Track Slabs
Authors: Bender Erich K.
Published: October 2005

In this paper the dynamic response, vibration isolation, and sound radiation of a resiliently supported track slab are analyzed. An analytical model is investigated which views railroad rails as beams fastened elastically to a slab which is resiliently mounted to a substructure. The slab is assumed to be a plate of finite width and infinite length. The analysis accounts for several different mechanisms of vibration transmission from the rail to slab, including structural nearfield, farfield, and coincidence effects. The results show that the slab is expected to be a very effective vibration isolator but will also behave like a sounding board at low frequencies. By proper choice of rail and slab parameters, this low-frequency radiation may be made comparable to the low-frequency sound ordinarily radiated by an electrically powered rail vehicle.
Reverberation-Time Measurements in the Philadelphia Academy of Music
Authors: West J. E. , Sessler G. M. , Flanagan J. L.
Published: October 2005

The reverberation time of the unoccupied Academy of Music in Philadelphia was measured utilizing the method of integrated tone-burst decays [M. R. Schroeder, J. Acoust. Soc. Amer. 37, 409 (1965)]. Third-octave tone bursts covering the frequency range from 50 to 5000 Hz were used as test signals. The measurements were taken at 14 different microphone positions throughout the Hall for two loudspeaker locations on stage. In addition, two different ceiling arrangements of the stage enclosure were implemented; namely, a flared tilt (normally used) and an experimental horizontal configuration. The subjectively important initial reverberation time T1 (extrapolated from the decay over the first 10 dB of the integrated response) as well as the final reverberation time T2 (extrapolated from the decay over the range −10 to −30 dB) were evaluated on a digital computer. The results for the octave centered at 500 Hz, averaged over all positions, are: T1 = 1.2 sec, T2 = 1.4 sec for the flared stage ceiling; and T1 = 1.3 sec, T2 = 1.5 sec for the horizontal ceiling.
Effects of Asynchrony on the Perception of Dichotically Presented Speech and Non-Speech
Authors: Porter Robert J.
Published: October 2005

Subjects were asked to identify both members of pairs of dichotically asynchronous (by 0 to 165 msec) stop consonant-vowel syllables or non-speech sounds derived from stop-vowels. For CV pairs, subjects tended to identify most accurately the temporally lagging syllables. As in previous studies [e.g., M. Studdert-Kennedy, D. Shankweiler, and S. Schulman, J. Acoust. Soc. Amer. 48, 599–602 (1970)], this lagging-syllable advantage (“lag effect”) was found at asynchronies up to 120 msec with a maximum effect at 60 msec. Lagging-signal advantages for the non-speech, when observed, were small, variable, and tended to occur over a smaller range of asynchronies. These non-speech results appear to be consistent with findings in previous non-speech masking studies. The pattern of lag effects observed for the syllables, on the other hand, indicate that the processing of these signals is particularly sensitive to the conditions of dichotic asynchronous competition, perhaps because special perceptual processing is required for the perception of speech. [Work supported by NIH.]
Digit Span Memory in Language-Bound and Stimulus-Bound Subjects
Authors: Day Ruth S.
Published: October 2005

Dichotic tests involving phonological fusion yield bimodal individual differences. Given items of the general form BANKET/LANKET, some subjects report hearing BLANKET. They report such fusions no matter which item began first. When specifically asked to report the leading phoneme, they report /b/ even when /l/ led by a substantial interval. Since they are reporting the phonological order permitted in English rather than the actual physical events, they have been termed “language bound.” Other subjects, termed “stimulus bound,” do not fuse and are better able to determine which phoneme led. Language-bound and stimulus-bound subjects, as defined by the dichotic fusion tests, took some digit-span memory tests. Nine digits were presented auditorily on each trial and subjects had to recall each item in the appropriate serial position. Stimulus-bound subjects displayed significantly superior memory. In digit-span experiments, performance is typically best at the beginning and end of the list, with a sizeable drop in percent correct for middle-of-the-list items. Stimulus-bound subjects showed only a slight decrease in recall for the middle items, whereas language-bound subjects showed a very great decrease. Implications concerning short-term memory capacity and stimulus encoding are discussed.
Noise Control for Gas Turbine Installations
Authors: Hoover R. M.
Published: October 2005

In the electrical utility application of a gas turbine, the primary noise problem is the control of noise radiated to the community. The industry has recognized this problem for some time and can provide good noise control measures. However, the initial acoustical performance of an installation can depend quite strongly on the communication between the buyer and the supplier regarding the noise sources, the noise criteria, and the noise specifications. In this regard, both the major and secondary noise sources for a typical installation are described in this paper along with some evaluation of common noise control measures. Also, some of the important steps in developing proper noise criteria and specifications are included.
Electrical Resistance Measurements of the Walls of the Guinea Pig Cochlear Channels
Authors: Sitko S. , Honrubia V. , Strelioff D.
Published: October 2005

Microelectrode pairs for current injection and recording of the resulting potentials were introduced into scala media, scala vestibuli, and scala tympani of the first three turns of the guinea pig cochlea; an additional pair of electrodes was placed in the neck musculature. The potential difference between each recording electrode combination was determined for direct current pulses passed interscalarly and from each scala to the neck. These potentials were used to derive values for the elements of simple cross-sectional resistive-network models of the lower three cochlear turns. It was found that the driving-point resistances between scala media and each of the perilymphatic scalae were nearly equal, having average values of 10, 8, and 6 kΩ in the first, second, and third turns, respectively. This resistance decline was concomitant with an increase in the scala media longitudinal attenuation factor which averaged 3 dB/mm in the first turn and progressively increased to 10 dB/mm in the third turn.
The Attenuation of Sound in Turbulent Pipe Flow
Authors: Ingard Uno , Singhal Vijay K.
Published: October 2005

The attenuation of sound resulting from the interaction with turbulent pipe flow is discussed. Theoretical and experimental results for both upstream and downstream propagation are compared. The role of this type of attenuation in practical applications is discussed. [This work was supported by the U. S. Navy (Office of Naval Research) under Contract N00014-67-A-0204-0019.]
Measurement of Vibration Patterns of Excised Larynxes
Authors: Baer Thomas
Published: October 2005

Experiments are described in which excised dog larynxes are used to simulate normal voice production. The larynx is mounted on a pseudo-trachea with a subglottal window so that the vocal folds may be viewed from both their superior and inferior aspects. Minute particles are placed on the vocal folds to locate distinct points and the positions of these points are tracked through a microscope in both the vertical and horizontal directions under stroboscopic illumination. Preliminary results have led to some insight into the complex wavelike nature of the vibration patterns. Motions of points on the superior borders of the vocal folds are primarily vertical, while motions of points on the lower medial surfaces have a larger horizontal component. Detailed pressure and airflow measurements will ultimately be made in conjunction with the mechanical measurements. The goal of this research is to understand better the detailed mechanism of phonation and to gather quantitative data for modeling. [This work was supported by NIH grants.]
The Role of the Middle Ear in Acoustic Trauma from Impulses
Authors: Eames B. L. , Hamernik R. P. , Henderson D. , Feldman A.
Published: October 2005

The purpose of this experiment was to evaluate the role of the middle ear in acoustic trauma following high-level impulse noise exposure. Eleven monaural chinchillas were exposed to either 161- or 166-dB peak SPL impulses of 1-msec “A” duration, presented at the rate of 1 per minute for 50 minutes. Auditory thresholds were measured before and at regular intervals after exposure, using the evoked response technique; middle-ear status was evaluated by means of impedance tympanometry. At 30 days the animals underwent tympanotomy for middle-ear examination followed by sacrifice for surface preparation histology. The 161-dB group showed the widest range of TTS with two animals exhibiting PTS. Tympanometric examination was suggestive of tympanic membrane stress (i.e., double-peaked tympanograms). The 166-dB group showed moderate TTS but no PTS; however, all animals had tympanic membrane perforations which required 10 to 30 days to heal. No gross changes were observed in the ossicular chains at tympanotomy. The results will be discussed in terms of a potential mechanism for histologic variability and individual susceptibility.
Cochlear Nucleus Neurons Response to TTS Producing Noise
Authors: Salvi R. J. , Henderson D. , Hamernik R. P.
Published: October 2005

The input-output function of neurons in the cochlear nucleus of the chinchilla was measured before and after exposure to 8 min of a 95-dB-SPL tone at the characteristic frequency (CF) of the neuron. Estimates of the traumatizing effects of the exposure were derived from threshold shifts measured by the auditory-evoked response. During the 8-min exposure the neuron's spike rate dropped between 5% and 70%. The threshold shift 0–5 min after the exposure was 5–20 dB for single neurons. The input-output functions reflected the loss of sensitivity and had a truncated dynamic range. When the input-output functions were normalized to preexposure values, the lower level of the function showed proportionately greater changes. The results of the experiment will be related to the generalized process of TTS.
Stationary Motor-Vehicle Noise Assessment in Semireverberant Spaces
Authors: Harford K. D. , Siddon T. E. , Kennedy D. S.
Published: October 2005

An earlier paper [J. Acoust. Soc. Amer. 51, 152(A) (1972)] discussed some early work done by acoustical engineering on no-load, semireverberant testing. The present paper describes the findings of the feasibility study completed on this type of testing and describes the equipment and facilities in operation in British Columbia to screen approximately 2000 vehicles per day. Semireverberant testing was found to be highly accurate. A control vehicle was measured on several different occasions, and the observed variation (standard deviation from mean =0.7 dBA) gives a realistic indication of the error. Contour plots of the SPL around a typical vehicle show that the measurements are relatively insensitive to microphone placement. Little correlation was found between the results of no-load tests and the S.A.E. drive-by test. When the characteristics of the vehicles used in the study were evaluated, several reasons for the poor correlation become apparent. These included narrow-band muffler characteristics, source directivity outdoors, repeatability of the drive-by test, and changes in exhaust noise with load. When a specific mode of vehicle operation under load is simulated on a dynamometer, much better agreement with the no-load test is anticipated. A program for complete motor-vehicle noise regulation is proposed which makes use of semireverberant no-load testing as well as total vehicle and muffler certification conducted at the manufacturers' level.
Speech Compression by Least-Squares Interpolation
Authors: Arcese A. , Goldberg A. J.
Published: October 2005

In this paper we present the theory and application of an adaptive interpolator which restores speech samples previously eliminated to lower the transmission rate. During waveform reconstruction, these detected samples are estimated as a weighted sum of neighboring past and future waveform amplitudes that were transmitted. These weights are chosen at the transmitter to minimize the averaged squared difference between the actual samples and the interpolated samples over an analysis length of 20 msec. Audio tapes will be played showing the results of quantizing the interpolation parameters.
Adaptive Quantization with a One-Word Memory
Authors: Jayant N. S.
Published: October 2005

We discuss a quantizer which, for every new input sample, adapts its step size by a factor depending only on the knowledge of which quantizer slot was occupied by the previous signal sample [1]. Specifically, if the outputs of a uniform B-bit quantizer are of the form Yu = PuΔu2; ±Pu = 1, 3, ⋯, 2B − 1, Δu>0, the step size Δr is given by the previous step-size multiplied by a time-invariant function of the code-word magnitude |Pr−1|: Δr = Δr−1 ⋅ M(|Pr−1|). The adaptations are motivated by the assumption that the input signal variance is unknown. Computer simulations have shown that, for first-order Gauss-Markoff signals, the optimum multiplier function M (which minimizes the mean-squared value of quantization error) has the property that it calls for fast increases of step size but slow decreases thereof. This property was first observed in a differential speech quantizer described by Cummiskey and Flanagan during the previous meeting of the Acoustical Society. In fact, there is a remarkable agreement between the actual multiplier values used in the speech quantizer and the optimum multipliers noted in the present study. Furthermore, with a Gauss-Markov input, changes in input signal correlation have a very small effect on the values of optimum multipliers. This seems to indicate that the afore-cited speech quantizer is quite robust, although it was designed with a limited set of speech inputs.
A Cell Model for Noise Propagation in Semi-Confined Spaces
Authors: Lyon Richard H. , Davies Huw G.
Published: October 2005

A cell model is used to discuss noise propagation in semi-confined spaces such as industrial manufacturing plants, downtown urban areas, and open plan offices. The cell walls are formed, for example, by buildings, walls, screens, machinery, or arrays of pipes. The walls reflect, absorb, and transmit sound. The noise sources within each cell represent, for example, machines or vehicles. The noise field within each cell has both a direct and a reverberant component, the reverberant component being determined partly by the acoustic power flow between adjacent cells. The sound level is predicted both within and exterior to an array of cells. Depending on the reflection, absorption, and transmission coefficients chosen, the sound level within the cell region may be either higher or lower than the level obtained when the noise sources but no cell walls are present; the exterior noise level is always reduced by the presence of the walls. It is shown that with a suitable choice of coefficients the model predicts reasonably well the ambient noise levels measured in urban areas.
Perturbation Effects of Rigid Cylinders in the Vicinity of a Cylindrical Transducer
Authors: Radlinski Ronald P.
Published: October 2005

A series expansion of cylindrical harmonics is used to study the interaction of infinitely long, parallel cylinders. The transducer is taken to be a cylinder vibrating with a uniform radial velocity while the one or more “spectator cylinders” are assumed to be rigid. Unknown coefficients are calculated from the above boundary conditions by the use of the addition theorem which expresses cylindrical wave functions of one coordinate system in terms of the cylindrical wave functions of a second coordinate system. The perturbing effects of a single rigid cylinder on the farfield radiation patterns of the transducer are presented for several radii ratios. Self and mutual acoustic radiation impedances for the two body interactions are illustrated as a function of separation distance. Radiation impedances and patterns resulting from placing the transducer at the center of a circular array of rigid cylinders are also examined. [Work supported by NAVSHIPS Sonar Technology Division.]
Auditory Correlates of English Vowel Features
Authors: Godfrey John J.
Published: October 2005

The Analog Cochlea, an electronic model of inner ear function, produces surfaces representing the input to the auditory nervous system for a given audio stimulus. Thus, for speech, surface features which remain constant for a single phoneme or distinctive feature across speakers may be called the auditory correlates of that feature or phoneme. Some features have been reported on previously to this Society [J. R. Mundie and T. J. Moore, “Speech Analysis Using an Analog Cochlea, ” J. Acoust. Soc. Amer. 48, 131 (A) (1970 )]. A study of these auditory features of English vowels shows that they are often, but not always, isomorphic with the formants indicated by spectral analysis. This paper will compare the intra- and interspeaker variances in spectrographic formant measurements with those from Analog Cochlea surface features, using the same set of vowels pronounced by the same speakers of a single dialect.
Acoustic Correlates of Word Stress
Authors: Medress Mark , Skinner T. E. , Anderson D. E.
Published: October 2005

Results of earlier studies by other investigators indicate that the four primary acoustic correlates of word stress in English are fundamental frequency, the duration of the vowel nucleus, the amplitude of the acoustic wave, and the integral over the vowel nucleus of energy with time. Little, however, is known about how these parameters lnteract and trade off to produce stress. In this investigation, the above correlates were obtained for a corpus of 40 multisyllabic words repeated once in isolation by each of three male speakers. The corpus contains examples of two-, three-, four-, and five-syllable words. Vowels receiving primary stress are followed by both voiced and unvoiced consonants. In addition to the words spoken in isolation, the four parameters were measured for eight short carrier sentences containing 11 of the 40 words to consider how the encoding of word stress is affected by a sentence environment. All of the above parameters were examined to determine how they carry stress information, which are the most useful in estimating stress contours, and how the various correlates interact to produce perceived stress. Finally, a comparison is made between the results of this study and those obtained by other investigators.
Cross-Linguistic Study of Advanced Tongueroot
Authors: Lindau Mona , Jacobson Leon , Ladefoged Peter
Published: October 2005

The phonetic mechanism underlying the feature advanced tongueroot was investigated from radiographic and acoustic data in a wide variety of languages. As a measure of an independent gesture of advancing the tongueroot we took the ratio between pharynx-width at the tongueroot and tongue-height. Depression of the larynx and the hyoid bone accompanies the gesture of advanced tongueroot. As expected this results acoustically in the first formant being lowered and the second formant being raised for front vowels and lowered for back vowels. Results based on one speaker of Twi and one speaker of Ateso show that the two harmonizing vowel-sets in these languages are best accounted for by a feature of advanced tongueroot. Results from a cineradiographic study of American vowels do not entirely support the feature advanced tongueroot in English phonology. The speakers distinguish “tense” and “lax” vowels by different phonetic mechanisms. The same speaker may even distinguish “tense” and “lax” vowels differently for front and back vowels. Data from other languages, including Dho-Luo, German, and Swedish were also analyzed with respect to the gesture of advancing the tongueroot.
On the “Constant Total Amplitude” Theory of Final Syllable Lengthening
Authors: Oller D. Kimbrough
Published: October 2005

It has been suggested [B. Lindblom, “Temporal Organization of Syllable Production,” Royal Inst. Technol., Stockholm, Sweden, STL-QPSR 2, No. 3, 1–5 (1968)] that the greater duration of final syllables over nonfinal syllables is caused by a tendency on the part of speakers to maintain a constant total energy (amplitude) output on syllables of the same degree of stress. Since utterance-final syllables characteristically show drops in amplitude per unit of time, they are lengthened, according to the theory, in order to compensate for the amplitude drop. In the present study, it is shown that no amplitude drop occurs on the final syllables of interrogative utterances in English. It is further shown that final-syllable lengthening is just as great for interrogative as for declarative utterances. The theory cannot account for this result. Alternative explanations of finalsyllable lengthening are discussed.
Intracochlear Perfusion of Synthetic Perilymph: Controls and Applications
Authors: Brummett R. E. , Himes D. , Mitchell C.
Published: October 2005

The utilization of cochlear perfusion as a tool for the study of cochlear physiology is not new. Both perilymphatic and endolymphatic perfusions have been done. However in these studies little or no data were given to indicate that the cochleas involved in these experiments were damaged. For our studies a “synthetic perilymph” solution containing the following ingredients (millimoles/liter) was prepared daily just prior to use: NaCl, 136.8; KCL, 5.6; CaCl2, 2.16; NaHCO3, 11.9; MgCl2, 0.491; Na2HPO4, 0.352; glucose, 4.44. The pH of the final solution was 7.95–8.05. For perfusion, glass pipets were inserted into both scala media and scala tympani of the basal turn of the guinea pig cochlea. Perfusion of the perilymphatic space at a speed of 0.1 milliliters/min was continued for 2 min. The ac cochlear potential and/or the N1-evoked potential was monitored from a round-window electrode. In order to check for procedural damage, an electrophysiological assessment of the cochlea was made before and after drilling the cochlea for the insertion of the perfusing pipets, as well as before and after perfusing with the synthetic perilymph. Data on the effect of perfusing solutions containing neomycin, Na salicylate, and Na cyanide will be presented. In addition, the effect of temperature of the perfusing solution on cochlea electrophysiology will be discussed.
Cochlear Microphonics, the Resultant of Two Separate Sets of Generators
Authors: Karlan Marc S. , Tonndorf Juergen , Khanna Shyam M.
Published: October 2005

The typical shape of the CM input/output function cannot be explained on the basis of nonlinearity alone. However, it could represent the resultant output of two separate sets of CM generators, presumably the inner and outer hair cells, having the following distinct properties: (1) their individual input/output functions possess wider linear ranges than the resultant; (2) at low levels, the first set (o.h.c.) is more sensitive than the second (i.h.c.); (3) with increasing input, the output of the second set rises at a faster rate than that of the first; and (4) 120° < Δφ < 180° between both sets. This hypothesis involves a testable proposition, i.e., with reference to a given standard, the phase of the resultant function should change cumulatively over its “nonlinear” portion, reaching a value of Δφ−90° at the minimum point of the curve. This proposition was tested in cats and guinea pigs. The results supported the above hypothesis which is compatible with a large number of other previous CM findings. [Supported by several NIH grants.]
Octave Bandwidth Constant Beamwidth Underwater Receiving Array
Authors: Holden R. J. , Hixson E. L.
Published: October 2005

By a method described at the 79th meeting of the Society, a seven-element linear broadside array was designed to give a constant beamwidth of 26° from 10 to 20 kHz. Five elements spaced 12λ at 10 kHz comprised one array. Using three of these and two more, a half-size array with spacing of 12λ at 20 kHz was obtained. Each was filtered then combined to give the array output. The filter functions as specified by the directivity function were approximated since they were not realizable by real elements. The predicted and measured characteristics of the array are presented.
Effect of Edge Diffraction on Microphone Response to Transients
Authors: Lockwood J. C. , Wriout Wayne M.
Published: October 2005

A microphone suitable for the study of short-duration transients generally will be large enough to disturb the acoustic field. We have investigated this problem by studying the diffraction of an N wave normally incident on a rigid disk. We predict on the basis of linear theory that the signal at the center of the disk will be the pressure-doubled incident waveform followed by an inverted N wave of amplitude equal to that of the incident wave. The delay of the inverted N corresponds to the travel time from the edge of the disk to the center. When the average pressure over a circular area symmetric about the center of the disk is calculated, the fall times of the head and tail of the diffracted waveform are found to increase as the radius of the circular area is increased. Measurements with spark-generated N waves incident upon wide-band capacitor microphones in circular plane baffles have shown excellent agreement with the theoretical predictions. [This work was supported by the Office of Naval Research and the Air Force Office of Scientific Research.]
Implications of the Earthquake as a Stochastic Process
Authors: Iwan W. D.
Published: October 2005

Implications of the fact that earthquakes are a transient stochastic phenomenon are considered with particular regard to data collection, data analysis, and application to problems of structural response. Requirements on the type and distribution of measurement equipment are discussed. The most widely accepted techniques of data analysis are indicated and examples of earthquake response spectra are given. The differences between average or design spectra and some of the more important spectra from the San Fernando earthquake are discussed. Application of earthquake data to problems of structural response is considered with emphasis on the types of models required, techniques for analysis of nonlinear structures, and the special problem of structural collapse
Dynamic Response of Tall Buildings
Authors: Jennings P. C.
Published: October 2005

The presentation summarizes recent results relating to the response of tall buildings to strong earthquake motion and to dynamic testing. Specific topics include forced and ambient vibration tests of a 22-story steel-frame structure, computer-aided analysis of the response of tall buildings to artificial earthquakes, as used in design, and the measured response of tall buildings to the recent San Fernando earthquake. For two major buildings in Los Angeles where results are available, comparison of the measured response at upper levels in the San Fernando earthquake to that predicted from analyses employing themeasured base response showed good agreement, encouraging the use of such analyses in the earthquake-resistant design of tall buildings.
Design and Simulation of Digital Filter Banks for Speech Analysis
Authors: Schafer R. W. , Rabiner L. R.
Published: October 2005

Short-time spectrum analysis is the basis for many speech analysls systems. Although the fast Fourier transform is generally used to perform spectrum analysis on a general purpose computer, a bank of recursire digital bandpass filters may be the best approach for hardware realizations. This paper discusses the analysis and design of digital filter banks composed of equal-bandwidth, equally spaced, bandpass filters. It is shown that significant improvement in the frequency response of the composite filter bank can be achieved by appropriate choice of the relative phases of the bandpass filters. Also discussed is an efficient general purpose computer simulation of a bank of recursire digital filters as required, for example, in a phase vocoder analyzer [Flanagan and Golden, Bell Syst. Tech. J. (Nov. 1966), This simulation uses the fast Fourier transform to compute filter outputs at a low sampling rate (approximately 100 Hz). For synthesis, the spectrum parameters are interpolated to a 10-kHz sampling rate using a finite impulse response digital low-pass filter. Design examples and recorded demonstrations illustrate the results.
Auditory Distortion Products f2−f1 and 2f1−f2
Authors: Hall J. L.
Published: October 2005

Two primary tones of frequencies f1=350 to 1500 Hz and f2=1.1 to 1.5 times f1 were presented monaurally at 60 to 80 dB SPL. Nonlinear distortion products at both f2−f1 and 2f1−f2 were made to beat against low-intensity probe tones slightly mistuned from the frequency of the distortion product. Subjects adjusted the amplitude and phase of cancellation tones at the frequency of the distortion products to eliminate the beating. The amplitude and phase of the 2f1−f2 cancellation tone agree with earlier observations [J. L. Goldstein, J. Acoust Soc. Amer. 41, 676–689 (1967)]. The amplitude and phase angle of the f2−f1 cancellation tone decrease with an increase of either f1 or f2/f1.
Aural Harmonics: A Possible Relation to Loudness
Authors: Clack T. D. , Erdreich J.
Published: October 2005

Two aspects of auditory function vary as frequency is lowered: (1) the rate of loudness growth for pure tones increases, and (2) at equivalent SLs, the magnitude of harmonic distortion (CM) is greater. Noting these relationships, Wever, hypothesized that the central summator yields a sensation of loudness based on its total input and that the neural responses caused by a pure tone fundamental (f1) are incompletely differentiated from the excitation of its aural harmonics. Such reasoning also suggests that dissimilarities in loudness growth rates between individuals at any particular f1 may be directly related to differences in their aural harmonic magnitudes. Four normals performed ratio (double/half) sealing at 1 and 2 kHz. Using these frequencies as f1's, the second and third harmonics were also estimated from tone-on-tone masking measurements [60–90 db (SPL) at 10-dB intervals]. These distortion estimates further support description of aural harmonic growth by the power law. The covariation of aural harmonic magnitudes and loudness growth rates are not clear for f1 = 2 kHz. For f1 = 1 kHz, however, an inverse relationship is evident. This finding suggests that for intensities at which aural harmonics are masked, their contribution to the loudness of f1 may be subtractive rather than additive.
Quantifying the Efficiency of BUDTIF Modifications
Authors: Campbell R. A.
Published: October 2005

While carrying out a Monte Carlo simulation project aimed at evaluating modifications of the BUDTIF (block up and down, two-interval, forced-choice) psychophysical procedure aimed primarily at improving this procedure's efficiency for an application in which a bad choice of initial starting level would frequently occur, it became evident that the usual way of viewing the efficiency of sampling was not completely satisfactory. Usually, some formula of the type Vs = Vp/eN, where Vs is the variance among repeated parameter estimates, samples; Vp is the variance of the population, psychometric function; N is the number of observations or trials; and e is some value of efficiency, with a value of 0.65 being a possible upper limit, has been used. The formula Vs = Vp/[e(N−n)], where n is some number of trials, related to those lost in the initial run-down, has proven useful in evaluating various modifications to the BUDTIF procedure by permitting the run-down ability to be quantified separately from the efficiency after the “threshold” region has been arrived at. Various possible modifications and their effects, when viewed as described above, will be presented.
Temporal Discrimination of Noise Bursts
Authors: Abel Sharon M.
Published: October 2005

Subjects were required to discriminate between two noise bursts, T and T+ΔT, in duration. The just noticeable difference in duration, ΔT, for 75% discrimination was determined for values of T ranging from approximately 110 to 1000 msec. The results show that the slope of the function relating log ΔT and log T is about 12 for values of T less than 80 msec. The slope increases to approximately 34 for longer T. Performance is not affected by a change in amplitude from 85 to 65 dB SPL, or by a change in bandwidth from 3500 to 200 Hz. Similar results were obtained with tone bursts of 1000 Hz. This discrimination of filled durations is substantially better than the discrimination of silent durations observed in a previous study. The data are compared with the predictions of several current theories of time perception. [This research was supported by the National Institutes of Health, Public Health Service, U. S. Department of Health, Education, and Welfare, while the author held a National Research Council of Canada Postdoctorate Fellowship. at the University of California, San Diego.]
Control of Noise from Machinery
Authors: Baade Peter K.
Published: October 2005

At the session on machinery noise at the Purdue Noise Control Conference, seven papers were presented dealing mainly with the acoustic information needed for the proper selection and application of machines to meet appropriate acoustic specifications. Blazier's paper dealt with noise from large centrifugal compressors used in air conditioning systems. Schuder's paper dealt with the prediction and abatement of noise from high pressure gas control valves. Mitchell presented the purchasers's and manufacturers's views on noise specifications for gear transmissions. Faulkner's paper reported research into the radiation of noise from hermetic refrigeration compressors. Tseo provided information for estimating the performance of wall structures used for controlling machinery noise. Szerlag discussed the factors involved in the noise generation of hydraulic components. Hubert reported results of extensive studies of flow noise of grilles.
Exact Ray-Theory Solutions for Two-Dimensional Velocity Variation
Authors: White D. , Keir D. L.
Published: October 2005

This paper presents exact ray-path and travel-time equations using solutions to the eikonal equation for a general class of sound velocity profiles which vary with range as well as depth. In the past, ray-theory for two-dimensional velocity variation has been treated mainly by numerical methods. Exact solutions have been available for only a few profiles of a very simple form. In this paper the velocity profile is expressed in terms of α and β of a transformed coordinate system in which α(z,r) and β(z,r) are functions of the depth, z, and range, r. This transformation and velocity function are such that the transformed eikonal equation reduces to a partial differential equation separable in α and β. The rotation of a velocity profile which depends on depth only is the simplest example of this approach. There are, however, transformations which lead to new velocity profiles not previously considered in the literature. The exact ray-path solutions and an equation for travel time are presented in terms of the α and β variables.
Acoustic Microscopy
Authors: Korpel A.
Published: October 2005

The new field of acoustic microscopy, still in its very infancy, may yet succumb due to irrelevance. On the other hand, it may prove to be extremely useful provided the mechanical wavemotion of sound indeed reveals important microscopic structures, not made visible by either light or electrom microscopy. Some evidence for this conjecture exists at the macroscopic level as will be shown. In any case, the question seems worth investigating and to do that one has to first build an acoustic microscope. This has now been achieved to some extent and systematic evaluation by visualization of biological tissue is being planned. The paper will trace the history of acoustic microscopy, describe the principal methods currently in use and discuss the latest experimental results which show walls and nuclei of biological cells.
Development of Binaural Time-Delay Apparatus for Improving Intelligibility of Speech
Authors: Gasaway Donald C.
Published: October 2005

A variety of electroacoustic instruments and devices have evolved in attempts to improve the perception and discrimination of aural signals and messages. This paper describes instrumentation that delivers binaurally time-delayed signals that trend to enhance the intelligibility of speech signals delivered to subjects. The electroacoustic device reported in this paper can be used to improve the intelligibility of desired signals when immersed in masking noise. The device used to achieve binaural time-delays encompasses completely variable delays ranging from 0 (in-phase) to 1500 msec. This device has proven of considerable value in situations where desired speech signals coexist with masking or other interfering noises, such as voice recordings obtained within cockpits of aircraft. Practical applications of binaural time-delay phenomenon are discussed.
Use of Shadowing in Speech Quality Evaluation
Authors: Pierce Linda , Silbiger Herman R.
Published: October 2005

The process of listening to speech over earphones, and simultaneously repeating it is called “shadowing.” The use of shadowing as a possible method for evaluating speech transmission quality was investigated. Three methods were used for degrading speech quality: additive noise, speech correlated noise, and peak clipping. All speech was presented over earphones. Subjects practiced the shadowing test to an 85% corrcet criterion on undegraded speech, with a word presentation rate of 1.31 words/sec. A male and a female speaker were used. With all three degradations, shadowing accuracy was monotonically increasing with decreasing degradation. For a given signal-to-noise ratio, performance was better while listening to speech correlated noise than while listening to additive noise. Shadowing was found to be more sensitive to low levels of peak clipping than most types of intelligibility tests.
Pause Frequency in Fluent and Nonfluent Speech
Authors: Love L. R. , Starbuck H. B. , Christensen J. M.
Published: October 2005

Earlier experiments determined that a significant difference in the frequency of brief pauses (150 msec or longer) in speech did exist between stutterers and nonstutterers. A Speech-Pause counter, which had been developed earlier [Love and Jeffres, (1971)] was calibrated to count pauses of 150-, 200-, 250-, and 300-msec durations. Pre- and post-therapy samples of the speech of 48 stutterers were taped. Each subject completed 6 weeks of intensive therapy in a resident stuttering clinic. These taped samples were processed through the Speech-Pause counter. The data indicate a significant change in the post-therapy sample, in the mean frequency of the 200-to-250-msec pauses. This result is surprising in the light of recent research which indicates that the 200-msec-pause duration is the threshold of resolution in the auditory system. The data in the post-therapy sample were compared with the data from normal subjects [Love and Jeffress (1971)] and were found to be highly similar. Possible implications concerning the use of the auditory feedback system are discussed. [This research was by a grant from the State University of New York Research Foundation.]
An Example of Relative Perception of Vowels
Authors: Boehm J. F.
Published: October 2005

In the course of testing a part of the vowel perception model proposed by Huseyin Yilmaz, a tape was prepared in which the spectrum was distorted in certain ways. The effect is sufficiently striking to warrant exposure, although the theory is not completely tested. For the demonstration, a vowel is filtered in such a way that in isolation it sounds like another vowel. When this acoustic event is imbedded in a sentence all of which is similarly filtered, it is perceived as the original vowel. This effect supports a relativistic theory of vowel perception.
Masking by Single and Double Sinusoids
Authors: Booth J. C. , Brandt J. F.
Published: October 2005

Two-sinusoid masking results reported earlier [J. C. Booth and J. F. Brandt, J. Acoust. Soc. Amer. 48, 77(A) (1970)] demonstrated a peak (increase) in the masking audiogram that was dependent on spacing and SPL of the maskers. As spacing was increased, this peak occurred at a higher test frequency. In the present study, the effect of the individual components in the two-sinusoid masker on a test frequency located between the maskers in the region of the peak was of interest. Masking data for one and two sinusoids are reported. Masked thresholds were obtained in three conditions: masker(s) above, below, and combined (40 dB SPL) for spacings of 100, 300, and 500 Hz at test frequencies from 400 to 3000 Hz. More masking was observed for the higher component than for the lower. The relation between the three masking patterns was found to be dependent on spacing. For the 500-Hz spacing, the combined maskers' pattern was not distinguishable from the masker-above pattern. For the 100-Hz spacing, the combined maskers showed summation of masking over all frequencies. The results of this study could be explained by the overlap in the displacement patterns of the signal and masker(s) on the basilar membrane.
Bone Conduction Testing by a Specially Designed Magnetostrictive Vibrator
Authors: Khanna Shyam M. , Tonndorf Juergen , Coe Eric
Published: October 2005

The device delivered BC signals at intensities up to 108 dB SL. An accelerometer built into its contact point monitored the applied signal. Even at high-output levels, the harmonic margin was in excess of 30 dB. Contact pressure could be exactly maintained. With the vibrator applied to the forehead and input held constant, air/bone cancellations were carried out, while contact pressure and contact area were being varied. A threefold increase in contact area, for example, required the AC signal to be raised as much as 35 dB. Magnitude and direction of these changes were frequency-dependent. Using known SPLs during AC/BC loudness matching facilitated determination of BC thresholds which, in terms of input acceleration, were much lower, by as much as 30 dB, than those reported earlier. These experiments suggest that specifications of BC thresholds by determining acceleration or displacement are mere approximations. More precise specifications should be based upon the power delivered to the skull, i.e., force × velocity × cosθ, θ being the phase angle between force and velocity. [Supported by NIH grants.]
Case Study of Power Plant Noise in a University and Residential Neighborhood
Authors: Bradley W. E. , Salter C. M.
Published: October 2005

Noise surveys were conducted in the vicinity of and inside the Niagara Mohawk Power Company 365 Mw, four-unit steam station at Oswego, New York. Neighborhood SPL measurements were made both day and night at nine sites within 600 to 2000 ft of the plant. An inventory of the land usage in the area is presented. Typical octave band sound pressure-level measurements are given along with dBA contours around the plant. Measurements taken within the plant delineate the primary noise sources and reverberant noise levels. Comparisons made of the measured and calculated SPLs in the community confirm the suspected noise escape paths. Criteria are established for a new 800-Mw unit based upon a nondegradation policy toward the present sound levels. Special recommendations are made for the wall and roof construction, ventilation silencers, and fan room enclosures to ensure that the new unit meets the specified criteria.
Magnitude Estimation and Paired Comparisons as Methods for Evaluating Acceptability of Aircraft Noises
Authors: Clarke Frank R.
Published: October 2005

The Point of Subjective Equality (PSE) for each of 15 pairs of aircraft noise was obtained using both the magnitude estimation technique and the method of paired comparisons. The methods were judged to be equally valid. The two methods differ in several ways. The method of paired comparisons appears to have greater face validity to observers and data analysis is relatively free of assumptions. However, the method of paired comparisons shows a “time error” (approximately 4 dB on the average) while the magnitude estimation technique does not. Further, the magnitude estimation technique appears to be more efficient; for a given level of reliability it requires approximately 50% of the testing time required by the paired comparisons method. Data will be presented and discussed. [Research supported by NASA-Langley Research Center: Contract NAS1-10017.]