bluuebunny/crossref_metadata_2025 huggingface dataset:
Long-term power spectra as speaker identification cue in simulated forensic situations
Authors: Johnson C. C. , Hollien H. , Doherty E. T.
Published: October 2005

The application of long-term power spectrum (LTS) to the speaker identification problem has shown reasonable promise in the laboratory environment [E. T. Doherty. J. Phonetics 4, 321–326 (1976)]. The present study attempts to utilize LTS in a situation that more closely parallels actual field application. Three “crimes” involving telephoned messages were simulated; each of the telephone calls was recorded simultaneously on both a reel-to-reel tape recorder via direct hookup and on a cassette recorder via a suction cup tap. All subjects (talkers and “suspects”) were volunteers drawn from a group of cooperating law enforcement agents. Two sets of twelve suspects each were recorded for the first two “crimes”; suspects for the third “crime” were drawn from a pool consisting of the two previous sets of individuals. All evaluations were conducted on the basis of a closed set paradigm. Sixteen and eight second samples from each set of unknowns and suspects were recorded and then subjected to power spectra analysis; the resultant data sets were analyzed by discriminant analysis, a pattern matching statistical technique. Preliminary results indicate that the LTS method does not perform as well as a speaker identification cue under forensic conditions as it does in the laboratory. Since system frequency response is of substantial importance to the long-term spectra technique, the observed degradation in LTS performance appears to be due (at least in part) to limitations in equipment and in the communiction channels utilized in the research.
Experimental investigation of the noise environment of a propeller driven light aircraft
Authors: Byrd R. , Cates B.
Published: October 2005

The increasing use of general aviation aircraft as a major mode of transportation has stimulated interest in interior cabin noise. A program to study this problem has been developed at North Carolina State University. The initial phase of the program entails an experimental investigation of the noise environment of a typical propeller driven, light aircraft powered by a reciprocating engine. Preliminary testing revealed the propeller and engine exhaust to be the dominant noise sources. The major paths by which airborne sound enters the cabin were found to be the windows and the window and door seals. These preliminary studies were used to determine problem areas for further investigation. Further experimentation explored the relative importance of sound transmission through windows, increased sound radiation due to window resonances, and flanking around window and door seals. The investigation concluded that further studies should be devoted to the parameters governing sound transmission through the windows. [This project supported by the NASA Langley Research Center.]
Noise of optical character reading machines
Authors: Daley W.
Published: October 2005

The manufacturer of a machine for optical character reading requested assistance in solving the noise problems resulting from a new design. The noise of the new machine was at such a level as to bar its acceptance by potential clients. Initial sound level readings, tape recordings and real time analysis resulted in identifying problems with noisy gears, nonisolated panels, loud bushings, shafts and paper slap. Recommendations were made to the manufacturer and subsequent changes resulted in lower sound levels. New sound measurements indicate other areas for noise reduction which are in the process of being incorporated into the final design. [Student Research Project.]
Navy Underwater Sound Laboratory and the cylindrical array
Authors: Nash H. E.
Published: October 2005

On 1 July 1945, the sonar development program of the Harvard Underwater Sound Laboratory (HUSL) was transferred to the United States Navy Underwater Sound Laboratory at New London, Connecticut (USNUSL). Especial emphasis was placed on the continuation of research and development work on scanning sonar systems at New London. Major developments initiated by HUSL were completed and evaluated; these included an integrated search-attack sonar involving both horizontal and vertical scanning and an electronically scanned cylindrical transducer for submarine applications. USNUSL continued the exploitation of the versatility provided by the cylindrical array in development of the concepts incorporated in modern surface ship sonar systems and extended these concepts to the spherical arrays of modern submarine sonars.
Directional patterns of transducer array
Authors: Kendig Paul M.
Published: October 2005

The historical development of directional beam patterns of planar transducer arrays consisting of a relatively large number of electroacoustic transducing elements is outlined. Special attention is given to the Dolph-Chebyshev method of shading (tapering) the array elements to achieve minor lobe reduction. This method originally considered an array of uniformly spaced, co-planar elements that were all driven in phase; thus, giving a farfield directional beam normal to the plane of the array. When the constant phase requirement is relinquished, super directive, difference, and tilted beams including endfire arrays are achieved. Some attention is also given to the practical aspects of achieving the desired results.
Sparse array performance
Authors: Greene C. R. , Wood R. C.
Published: October 2005

A sparse array is formed from a linear equi-spaced array by omitting elements and substituting self- and crosspower terms from remaining elements to preserve the pattern and gain characteristics of the full array. However, the output noise is generally increased for any given averaging time. Analytical techniques permit evaluating the output noise for any sparse array under general conditions of substitution scheme, signal-to-noise ratio, and interelement noise correlations. An optimum substitution scheme is selected from a linear combination constrained to give identical patterns for the sparse and full arrays. For example, omitting an inner element of a four-element array increases the output noise by 3.2 dB when the signal and correlations are zero (the worst case); for an SNR of −3 dB, the noise increase is 1.1 dB. When the interelement correlation is 0.10, the noise increase is 2.2 dB for zero signal. In a five-element array with zero signal and uncorrelated noise, omitting the center element increases the noise by 2.7 dB but omitting either of the other two inner elements increases the noise by just 2.2 dB.
Physiologic and audiometric indices of noise susceptibility
Authors: Bennett T. E. , Bienvenue G. R. , Michael P. L. , Anthony A.
Published: October 2005

Interdisciplinary experiments involving human and animal subjects exposed to noise were conducted to investigate relationships among noise induced changes in (1) circulating hormone levels (ACTH and cortisol), (2) neuronal metabolism (auditory cortex, hippocampus, hypothalamus), (3) endocrine structures (pituitary-adrenal axis), (4) cochlear elements (spiral ganglion, hair cells), (5) pure-tone thresholds, (6) level of initial masking, (7) Loudness Discrimination Index, and (8) galvanic skin response audiometry. The overall results support the hypothesis that certain noise induced hearing changes may be hormonally mediated. Furthermore, two of the above procedures, the Loudness Difference Index and the hormone assay show promise as early indicators of individual noise susceptibility. [This project was funded, in part, by a Rockefeller Foundation Grant-in-aid.]
Acoustic masking of electrical stimuli
Authors: Frederickson C. J. , Gerken G. M.
Published: October 2005

Behaviorally measured detection threshold for electrical stimulation of cochlear nucleus was elevated in cats when masking noise (20 msec duration; 75 dB re 0.0002 dyn/cm2 was synchronized with the electrical stimuli. Three factors influenced masking: (1) Stimulation site: For electrodes in cochlear nerve, cochlear nucleus, or trapezoid fibers, masking noise elevated electrical detection thresholds by +4 to +11 dB; for electrodes bordering on auditory structures, maximum elevation was +2 dB. (2) Timing: Maximum masking occured when the stimulus pulse just followed the calculated onset of masker-evoked activity in cochlear nucleus; progressively less masking occured at longer onset-to-onset intervals, and little masking occured when stimulus pulse preceded or followed the masker. (3) Masker frequency: With pure tones, masking was maximal at a particular frequency for each stimulation site and was progressively reduced for maskers above or below the optimum frequency. It is concluded that masking occurs when stimulus and masker activate the same population of cochlear nucleus neurons. Masking functions may thus reflect the response characteristics of small aggregates of electrically stimulated neurons.
Tuning curves of brainstem potentials in the guinea pig
Authors: Mitchell Curt , Fowler Cynthia G.
Published: October 2005

The frequency specificity of the brainstem response is described. In a recent study, Dallos and Cheatham [J. Acoust. Soc. Am. 59, 591–597 (1976)] described tuning curves of the cochlear action potential. The present study describes tuning curves of cochlear action potential N1 and the brainstem potential N3 (seen as a vertex positive potential, latency 5–6 msec). The N1 potential was recorded from a pair of electrodes in the cochlea while N1, N2 and N3 were recorded from the vertex of the skull. Tone bursts were used to elicit the evoked potentials, and continuous tone maskers were used to determine the tuning curves of these potentials. The sharpness of tuning, indicated by Q10, and the overall shape of the tuning curves were the same for the N1 and N3 potentials. However, slightly more intensity was needed to mask N3 than N1. The significance of this slight resistance to masking is not apparent. The frequency specificity of brainstem potentials are considered important for extending the clinical usefulness in humans.
Effects of noise exposure on latency and strength of contraction of the middle-ear muscles
Authors: Gerhardt Kenneth J. , Melnick William , Ferraro John A.
Published: October 2005

Measurements of latency and strength of contraction of the chinchilla middle-ear muscle (MEM) reflex were obtained before, during, and after an eight-hour exposure to octave-band noise centered at 0.5 kHz at 95 dB SPL. The animals were chronically implanted with round-window recording electrodes. A 0.5 kHz tone delivered to the same ear elicited reflex activity. Temporal changes in the envelope of the cochlear potential (CP) reflected on-set latency. Strength of contraction was inferred by measuring amplitude decrements in the CP produced by a low-level, continuous 0.3 kHz tone. The threshold of the reflex increased an average of 4 dB with each additional two hours of exposure. The level of the signal used to elicit the reflex for samples of latency and strength of contraction was adjusted to 10 dB above threshold established during each test interval. Noise exposure resulted in a reversal of the normal inverse relationship between latency and strength of contraction with increasing intensity of the reflex eliciting sound. As the duration of the exposure increased both latency and strength of contraction increased.
Physiological masking in single auditory-nerve fibers: “Line-busy” or saturation?
Authors: Smith R. L.
Published: October 2005

According to the classical “line-busy” hypothesis, maskers act by preempting available transmission channels, i.e., auditory-nerve fibers, thus making them unavailable to respond to signals. This hypothesis has been questioned since Kiang et al. [MIT Research Monograph 35 (1965)] found that the total firing rate produced by a signal plus a masker could be smaller than the rate produced by the signal alone. However, the physiological masking effect may have a simple explanation based on the saturation of transmission channels located peripherally to the sites of adaptation and spike initiation. This possibility is based on auditory-nerve studies which show that a sufficiently intense background tone produces peripheral saturation and eliminates the single-fiber response to a superimposed increment in sound intensity [Smith and Zwislocki, Biol. Cybern. 17, 169–182 (1975)]. In addition, when the background onset occurs sufficiently before the increment onset, the total firing rate is reduced by adaptation. New data are presented to support this contention and demonstrate that wide-band backgrounds produce saturation and adaptation effects similar to those previously described for characteristic-frequency backgrounds.
How safe is 115 dBA for 15 minutes?
Authors: Johnson Daniel L. , Schori Thomas R.
Published: October 2005

The current OSHA noise standard permits maximum occupational noise exposures equivalent to an 8-h, A-weighted level of 90 dB. Since equivalency is defined in terms of the 5-dB halving rule (i.e., for each 5-dB increase in noise intensity, exposure duration is halved), this standard permits a 15-min noise exposure at 115 dBA. Higher intensity exposures, however, are considered hazardous and, consequently, are not permitted no matter how brief the exposure duration. Is 115 dBA for 15 min safe? Probably not. TTS2 data collected in a recent study by the second author (Schori, 1976) suggest that a 115-dBA exposure for 15 min may be quite hazardous. Forty subjects (80 ears) were exposed to pink noise at 115 dBA for only 2.7 min. Yet this relatively brief exposure produced a TTS2 in one ear of one subject of 47 dB and produced TTS2's greater than 20 dB in six ears (five subjects). The median TTS for both ears combined was 8 dB. On the other hand, data from the same study suggest that all noise exposures above 115 dBA are not necessarily hazardous. For example, 40 subjects exposed to 130-dBA pink noise for 10 sec exhibited virtually no TTS2 while the same subjects exhibited only moderate TTS2 (a median TTS2 of 2 dB) when exposed to 120-dBA noise for 40 sec. Thus, the 115 dBA limitation may be overly restrictive while at the same time too lenient. No single equivalency rule, such as the 5-dB rule or the 3-dB rule, is completely adequate for all possible exposure durations. The 3-dB rule appears to be sufficiently protective for noise exposures of 85–130 dBA while the 5-dB rule, though, does not.
Presumed noise induced permanent threshold shift resulting from exposure to an Leq of 89 dBA
Authors: Berger E. H. , Royster L. H. , Thomas W. G.
Published: October 2005

The noise induced permanent threshold shift (NIPTS) resulting from up to ten years of exposure to an Leq of 89 dBA was investigated. Prior occupational noise exposure was controlled for by eliminating subjects with previous high noise level jobs or uncertain exposure histories. The final population consisted of 42 males and 58 females working in steady state broadband noise environments with octave band spectra sloping at approximately −1.0 dB/octave. No attempt was made to screen subjects for any auditory pathology. A 222-subject control group from the same geographic area as the exposed subjects was selected, such that none of its constituents had any effective industrial noise exposure. Military service and nonindustrial noise exposure were common to both the control and exposed subjects. Presumed NIPTS was calculated by correcting each individual audiogram of the exposed subjects, according to the sociocusis curves developed from the control population hearing levels. The results indicated a considerable male-female difference in NIPTS, even though both groups were exposed to the same Leq. Averaging the results for all 100 subjects, in order to make comparisons to other available data, yielded results in close agreement to predictions based upon the work of Burns and Robinson, Baughn, NIOSH, and Passchier—Vermeer, indicating that ten years of exposure to a daily Leq of 89 dBA causes measurable hearing loss at 4 kHz. [Work partially funded by a grant from the Rockefeller Foundation.]
Test battery approach to the early detection of noise-induced hearing impairment
Authors: Bienvenue G. E. , Michael P. L.
Published: October 2005

Current practice in the examination of hearing impairment has not proven to be effective in the early detection of noise-induced hearing impairment. This paper describes a battery of two tests based upon temporary threshold shift (TTS) and loudness discrimination measurement procedures thereby providing an examination of two different parameters of hearing change. The TTS test procedure uses conventional techniques, but the loudness discrimination procedure, the Loudness Discrimination Index (LDI), was developed specifically for this purpose by the Environmental Acoustics Laboratory. Data obtained with experimental subjects who had been exposed to brief, high-level sound showed that the LDI is a valid indicator of temporary, noise-induced, hearing change. In addition, LDI test results appear to be free of testing artifact and can reflect hearing changes not detected by TTS. It is anticipated that the LDI could be included with the traditional TTS measurement in a test battery for use in the early detection of noise-induced hearing impairment.
Auditory effects of long exposures to noise. II. Temporary threshold shifts produced in humans by dairly exposures to a tailored, wide-band noise
Authors: Mills J. H. , Gilbert R. M. , Adkins W. Y.
Published: October 2005

Groups of human subjects were exposed for 8 h on consecutive days to a tailored, wide-hand noise. This noise was composed of octave-bands centered at 0.5, 1.0, 2.0, and 4.0 kHz. For one of three exposures octave-band levels were identical to those used in a previous study. A-weighted sound levels of the exposures, which were held on separate occasions, were 91.5, 87, and 81 dB. The 81-dB exposure produced threshold shifts of about 10 dB near 4.0 kHz. For the 87- and 91.5-dH exposures threshold shifts near 4.0 kHz were independent or nearly so of the level of the noise. The major difference between the 87.0- and 91.5-dB exposures was in the spread of threshold shift along the frequency domain—the higher the noise level the greater the spread. Predictions of TTS audiograms from data for single octave bands were not especially accurate. In some instances the threshold shifts produced by the four octave complex exceeded the predictions of threshold shifts from single, octave-band data, whereas in other instances the reverse was true. Also, threshold shifts on day 1 always exceeded the threshold shifts observed on day 2. [Supported by NIEHS.]
Threshold shifts in chinchillas exposed to low-frequency noise
Authors: Burdick Charles K. , Patterson James H. , Mozo Ben T. , Camp Robert T.
Published: October 2005

Audiograms were obtained on eight binaural chinchillas trained on a shuttlebox avoidance procedure. Four chinchillas were exposed to three successive levels of an octave band of noise centered at 0.063 kHz: 100 dB SPL (74 dBA), 110 dB SPL (84 dBA), and 120 dB SPL (94 dBA). The other four chinchillas were exposed to these successive levels of an octave band of noise centered at 1.0 kHz: 75 dB SPL (75 dBA), 85 dB SPL (85 dBA), and 95 dB SPL (95 dBA). All exposures lasted 72 h. Maximum amounts of threshold shift (TS) of 20, 40, and 60 dB were found for the 1.0-kHz exposures at 1.4 or 2.0 kHz. At the highest level a 10-dB shift was present 30 days postexposure. Little TS was found for the 0. 063 kHz exposure at 100 and 110 dB. At the 120-dB exposure a TS of about 40 dB was found at 2.0 and 4.0 kHz and 10 dB remained at 2.0 kHz 30 days postexposure. Implication for human damage risk criteria will be discussed.
Effects of level of indoor illumination on the judged annoyance of aircraft noise
Authors: Shigeshisa T. , Gunn W. J.
Published: October 2005

Annoyance response to 27 recorded aircraft noise stimuli presented at levels ranging from 83.9 to 91.8 dBA (peak value) was measured by magnitude estimation, under three different levels of simulated living room illumination. One level of illumination was ordinary room brightness, and the other levels were either dimmer or brighter. Analyses of variance, performed on the slopes and intercepts of the annoyance function, showed that the illumination conditions were significant. Test/retest and split-half reliabilities indicated the annoyance measures were stable and consistent under the influence of illumination. There was a clear difference in both slope and intercept between dim and ordinary illumination, indicating that the annoyance is less at low noise levels and grows more rapidly with increasing noise level under dim than ordinary illumination. The regression lines of annoyance showed that, relative to ordinary illumination, the annoyance is (1) less under dim (31% annoyance reduction, or 5 dB equivalent attenuation) at an aircraft noise level of about 89 dBA and (2) less under bright (24% annoyance reduction, or 4 dB equivalent attenuation) at about 88 dBA.
The reduction of annoyance as a result of the addition of low-frequency noise
Authors: Turner Christopher W. , Burns Edward M.
Published: October 2005

Subjects judged the annoyance of pairs of noise bursts of indicating which member of the pair was “more annoying.” Each member of the pair consisted of a 5-sec burst of 13-octave-band white noise centered at 3150-Hz at levels of 85, 90, or 95 dB SPL. To one member of each pair was added a 13-octave-band of white noise centered at either 250 or 500 Hz at intensity levels ranging from 63 dB SPL to 115 dB SPL. The results show that for certain intensities of the low frequency bands, the combined noise bands were less annoying than the 3150-Hz band alone. Thus, in these cases, annoyance was reduced as a result of the addition of sound energy. This is in opposition to current theory concerning annoyance. The reduction of annoyance was more pronounced for the higher intensities of the 3150-Hz band, suggesting that the effect was due to a reduction of the “tickle” or distortion caused by the 3150-Hz stimulus.
Session NN. Noise IV: Outdoor Sound Propagation: A Special Workshop
Authors: McDaniel Oliver H.
Published: October 2005

The nature of sound propagation in the outdoor environment is an important consideration in the prediction of the noise impact from highways, airports, and railroads. Current noise prediction methods do not adequately account for the manner in which sound is attenuated with distance over open ground or through vegetation. A considerable amount of research has been conducted on outdoor sound propagation; however, a review of the literature shows that there are large discrepancies between various researchers for both open ground propagation and for propagation through forests. The results of theoretical analyses for the open ground case vary, depending on the boundary condition assumption. The assumption of a locally reacting ground surface results in a solution which appears to be valid; however, when the ground is treated as an elastic medium a different result is obtained. An additional deviation is obtained when the ground is treated as a layered elastic medium. It appears that the results of the various experimental studies may have been dependent on the particular test methods used and other factors. For both the experimental and theoretical studies there is no reason to believe at this point that any one approach is more valid than another. The purpose of this workshop session is to assemble the various scientists who have worked in the field of outdoor sound propagation to attempt to resolve the discrepancies between the studies and to formulate future research plans. The session will begin with several formal presentations of papers followed by a round table discussion. Although specific persons have been invited to this session, we welcome participation by anyone who has an interest in the subject.
Intracabin communication in light aircraft noise: subjective evaluations and talking levels
Authors: Rupf J. A.
Published: October 2005

As part of a study of factors affecting ride quality, the effect of general aviation cabin noise on speech communication between passengers was investigated. Twelve female subject pairs were seated side by side and required to converse with each other while being exposed to 5-min segments of noise. Three different noise types were presented at levels of 90, 85, 80, and 75 dB(A). After each noise segment, the subjects rated the noise effect on conversation, judged the noise as acceptable or not acceptable for conversation, and estimated how long they could converse comfortably in the noise. Fifty percent of the subjects judged 75 dB(A) as acceptable for conversing 1 h or longer. Throughout all testing, the subjects wore small boom mikes, which were attached to eyeglass frames, and measurements of talking level were made. A regression line fit to the entire data set showed a 6.4 dB(A) increase in talking level for a 10 dB(A) increase in noise level. Corresponding regression line slopes for individuals varied from 5.0 to 7.8 dB(A). [Work supported by NASA.]
Acoustic detection of high-energy particle showers
Authors: Blackinton J. G. , Bowen T. , Bradner H. , Jones W. V. , Learned J. , Levi M. , Linscott I. , Parvulescu A. , Pifer B. , Polakes P. , Strait J. , Sulak L.
Published: October 2005

Experiments of Brookhaven National Laboratory in October 1976 examined the acoustic radiation produced by high energy protons colliding with liquid water. In Experiment I, 1022 protons accelerated to 200 MeV by LINAC were stopped within about 20 cm after entering a large cylindrical tank. The acoustic pulses produced by the thermalization of the particles were bipolar (N shaped) with approx. 2000 μbar peak-to-peak. Proton pulse duration was varied from 3 to 200 μsec; the briefest acoustic pulse was about 30 μsec (consistent with the smallest dimension of the proton beam, the 5-cm diameter) while for the longer proton pulse durations the acoustic signal followed linearly. In Experiment II, the same proton flux (1011) was further accelerated to 30 GeV by the ACS, then fast-extracted and focused, yielding minimum durations of 5 μsec and diameter of 3 mm. The beam traversed an ordinary 55-gel barrel filled with water. It is well known that only a small fraction of the proton pulse energy (some of 1%–2%) is deposited in the approximately 40-cm water path; the beam was eventually stopped in the normal beamstop (30 m of steel). This acoustic pulse generation process yielded signals with frequencies in excess of 3 kHz (consistent with the 3-mm diameter of the beam). Peak-to-peak pressure was approximately consistent with the Experiment I (LINAC) results, but hydrophone recalibration is still pending due to radioactivity. These two experiments yield conversion efficiencies in the order of 10−9–10−10 for the parameter variations which produced particle shower energies of 1019–1020 eV; we find approximate agreement with the theory proposed by Askarian and Dolgoshaju (preprint), and also with the laser-related theory of P. Westervelt. Further work is planned for midsummer 1977 at Fernilab.
Ultrasonic field parameters measured by optical interferometry
Authors: Haran Michael E. , Harris Gerald R. , Bodine William
Published: October 2005

The use of optical interferometry for the measurement of ultrasonic field parameters was demonstrated by Mezrich et al. [RCA Rev. 35, (December 1974)] and applications have been reported by others [M. E. Haran and H. F. Stewart “Optical interferometric measurements of ultrasonic radiation and its applications to medicine,” NBS SP456 (1976)]. This system, known as the ultrasonovision, has recently been interfaced to a Hewlett—Packard 21MX minicomputer. The result is a decrease by a factor of twenty in the time required to analyze each frame of data. In addition, a method has been developed to make the system self-correcting in that its performance is unaffected by variations in the light level, slight optical misalignment, or variations in reflectivity of the pellicle membrane. Details of the interface and self-correction method are given. Present studies with this system include mapping the field emitted by plane and focused transducers of low megahertz frequencies as a function of distance from the source.
Influence of introducing ultrasound during solid state processing of metals
Authors: Fairbanks H. V.
Published: October 2005

This paper will summarize research studies in which ultrasound having a frequency of 20 kHz is introduced into processing of metals in the solid state. Included will be recrystallization and heat treatment processing. The recrystallization studies include the effects of ultrasound upon polymorphic transformations and reheating of cold worked metals. The heat-treating studies include the precipitation hardening process, tempering of steel and the decomposition of iron carbide in white cast iron. It was found that the introduction of ultrasound during the solid state processing of metals generally influenced the rate of reaction for the process, changed the grain morphology and increased the homogenuity of the product.
Effects of wind and temperature gradients on noise emission measurements at 15 m
Authors: Mansbach Peter A.
Published: October 2005

Simplified expressions have been obtained to describe the effects of wind and temperature gradients on sound ray propagation, using the geometry applicable to noise emission measurements at 15 m. The three principal effects are changes in the path-length difference between direct and reflected rays: changes in the angle of incidence of the reflected rays, which alters the reflection coefficient: and focussing of the reflected rays, which changes the intensity. These expressions have been applied to outdoor measurements of surface impedance.
Complex hydrophone calibrations using pseudo-Gaussian noise signals
Authors: McMahon G. W.
Published: October 2005

A computer-based hydrophone calibration system has been developed for the measurement of complex receiving sensitivity over a wide frequency band in an open water acoustic tank. A pseudo-Gaussian number sequence is generated for transmission into the tank via a digital-to-analog coverter, filter, power amplifier and wide-band projector. A cross spectral analysis is performed between the sampled hydrophone output and the corresponding number sequence, averaging over several independent noise records. This process is carried out both for the “unknown” hydrophone and a “standard” hydrophone using the same pseudo-Gaussian noise records and the same hydrophone position in the noise field. The amplitude and phase response of the unknown is calculated relative to the standard, which may be one hydrophone of a group to be calibrated or may be a calibrated reference standard. The system is usable over the frequency range 20–9000 Hz.
Acoustic radiation and interaction impedances for the nonuniform velocity of a cylindrical surface
Authors: Stepanishen Peter R.
Published: October 2005

A general approach is presented to evaluate the acoustic radiation and interaction impedances for the nonuniform velocity of a vibrating surface on an infinite cylinder. The approach is based on the use of a Green's function and Fourier transform technique. General integral expressions are developed for both the acoustic radiation and interaction impedances for a general velocity distribution on the cylindrical surface. The expressions are shown to reduce to previously developed expressions for the radiation and mutual impedances for several uniform velocity problems of interest. As a particular nonuniform velocity of interest, the radiation and interaction impedances are addressed for the in vacuo modes of a simply supported finite cylindrical shell. Simple expressions are presented as a function of the circumferential and axial mode number for both the low- and high-frequency behavior of the radiation and interaction impedances. Numerical results are presented to illustrate the general behavior of the radiation and interaction impedances of the low-order mode of interest.
Prediction of the ground effect: side-line noise from aircraft
Authors: Piercy J. E. , Embleton T. F. W. , Donato R. J.
Published: October 2005

A number of empirical schemes exist for prediction of the noise in areas alongside airport runways, but it has proved very difficult in practice to reach a concensus on any one of them. We have recently published the basic ingredients for calculating the effect of ground reflections for this case from first principles—namely, the relevant formulae and the spectrum of the impedance of grassland. The attenuation of noise from a JT8-D powered jet aircraft due to ground reflection has been calculated as a function of distance and angle above the horizon. A large attenuation (5–20 dB) is obtained for very small angles (smaller than about 3°) due to Lloyd's mirror cancellation: this varies strongly with angle and to a lesser extent on distance. A smaller attenuation (<3 dB) is obtained for larger angles (up to 90°) which is due to ground absorption: this varies with distance and only weakly on angle.
A time history algorithm for aircraft noise
Authors: Rackl R.
Published: October 2005

In the course of the development of a comprehensive computer airport noise model offering a choice of noise metrics (see previous paper), the ASDS metric (“Aircraft Sound Description System”) required the computation of the time noise levels from aircraft flyover exceed specified thresholds. A package of subroutines was developed that performs a noise level time history simulation by tracking aircraft position and orientation along a three-dimensional flight path using variable time steps depending on the rate of noise level change. The A-weighted noise levels at observer positions are calculated for each time step from two three-dimensional models: a three-component jet engine noise emission model (front fan, rear fan, jet) where each component varies with engine thrust at a different rate; and a propagation model describing the excess attenuation of A-weighted levels as a function of distance. Both models use aircraft specific empirical parameters determined from measured spectral data, and calibrated by comparing calculated and measured maximum A-weighted flyover levels for a range of practical distances. The subroutine package is capable of calculating threshold exceedance times, cumulative distributions of noise levels, and the time-integrated energy equivalent noise level from an aircraft flyover. [Work supported by the U. S. Department of Transportation.]
Information processing for pure tones in older adults
Authors: Corso John F.
Published: October 2005

The ability of three age groups to identify pure tones was measured by the method of absolute judgments. Group mean ages were approximately 20, 40, and 60 years, with 25, 20, and 18 subjects per group, respectively. Eight tones in equal logarithmic units from 100 to 8000 Hz were presented monaurally in random order in the better ear at a loudness level of 60 phons. After practice, subjects were required to identify each tone by a designated code number from one to eight (low to high frequency). The correct identification was provided after each judgment. These were 80 judgments per subject (10 trials × 8 tones). Analysis of variance showed a significant difference in the mean number of correct responses among age groups. The means in order of increasing age were 55.52 (69.39%), 51.55 (64.43%), and 48.44 (60.55%) (F ratio 8. 003, 2/120 df, p = 0.001). The last 40 trials yielded significantly better performance than the first 40 trials for the 20 and 60 year-old groups, but the 40 year-old group showed no change (F ratio 10.401, 1/120 df, p = 0.002). The age × trials interactions was nonsignificant. It is concluded that the processing of auditory information is adversely affected by normal aging in adults from 20 to 60 years. [Work supported by SUNY Research Foundation Grant No. 023-7185A.]
Discrimination measurement and experimental design. I. Variable-standard designs and categorical perception
Authors: Macmillan Neil A. , Kaplan Howard L. , Creelman C. Douglas
Published: October 2005

A continuous Signal Detection Theory analysis is presented for several variable-standard discrimination procedures (e.g., the ABX design) commonly used in psychoacoustic and speech experimentation. The analysis shows that obtained data, in terms of either percentage of correct responses or d′-like measures, underestimate the discriminability of pairs of signals, and that the amount of underestimation depends on both the particular procedure used and the performance level obtained. Performance on such discrimination tasks is often compared to identification performance, the data being used to evaluate the hypothesis that an auditory dimension is perceived “categorically.” These comparisons, however, have been based on a theoretical framework which assumes (low) thresholds; we offer a restatement of the categorical perception hypothesis in terms of the continuous model, and test the hypothesis with existing data. For cases in which perception is found not to be categorical, the model provides a means for distinguishing the hypothesis that discrimination results from dual processing of categorical and noncategorical information from other explanations.
Recognition of transposed tone sequences
Authors: Cohen Annabel J. , Cuddy Lola L. , Mewhort Douglas J. K.
Published: October 2005

Twenty 7-note standard sequences cross-classifield on 5 levels of harmony and 2 levels of contour were presented in a, two-alternative forced choice paradigm to two groups of musicians differing in level of musical training. Comparison sequences were transposed: on one-half the trials to the dominant (+7 of −5 semits), on the remaining trials to the tritone (± 6 semits). Each incorrect comparison contained one wrong note “out” by 1 semit. Ability to recognize the correctly transposed comparison increased with the simplicity of both harmony and contour of the sequence. In addition, there was a significant interaction of harmonic structure and key of transposition: diatonic sequences were easiest to recognize when transposed to the dominant; but, surprisingly, nondiatonic sequences were recognized best under tritone transposition. As expected, performance increased with past musical training of the listener. The results are interpreted in terms of a theory which considers separately a frequency and sequential code of the auditory stimulus. [Work supported by the National Research Council of Canada.]
Temporal modulation discrimination function
Authors: Ahroon William A. , Fay Richard R.
Published: October 2005

Temporal Modulation Discrimination Functions (TMDF)—the discriminability of the rate of amplitude modulation—were obtained. Human observers were asked to perform a same—different discrimination between two frequencies (f,f + Δf) of sinusoidally amplitude-modulated wide-band noise. Since the long-term power spectrum of this kind of stimulus is not altered as a result of the amplitude modulation imposed, modulation frequency discrimination data are considered to be measures of the temporal resolving capacity of the auditory system. For each observer, the function relating Δf/f to f is relatively flat between 50 and 200 Hz, with clear individual differences in overall discrimination capacity (Δf/f ranging between 1% and 6%). The TMDF's are compared with the Temporal Modulation Transfer Function [N. F. Viewmeister, J. Acoust. Soc. Am. 53, 312(A), (1972)] and other functions relating temporally encoded information as well as to pure-tone frequency-difference limens. [Work supported in part by NSF.]
Listeners' impressions of speakers with and without hearing losses
Authors: Blood G. W. , Blood I. M. , Danhauer J. L.
Published: October 2005

The purpose of this study was to evaluate listeners' ratings of normal hearing and hearing-impaired speakers' on the following four a priori factors: intelligence, achievement, personality, and appearance. Additionally, alterations in listener ratings were investigated as a function of whether or not subjects wore hearing aids regardless of speaker types. Recorded speech samples of four normal hearing, four hard of hearing, and four deaf children were used as audio stimuli; and two photographic slides of each child (one showing him wearing a hearing aid, and one showing him not wearing a hearing aid) served as visual stimuli. The stimuli were heard and seen by 150 normal listeners who rated various characteristics of the speakers on a semantic differential scale. Ratings were submitted to a multivariate analysis which revealed that listeners' impressions of speakers were “more negative” both when the speaker had “hearing-impaired” speech and when his photograph showed him wearing a hearing aid.
Experimental results on Tadoma
Authors: Reed C. M. , Durlach N. I. , Braida L. D. , Rabinowitz W. M. , Norton S. , Schultz M. C. , Chomsky C.
Published: October 2005

We have initiated a study of speech perception through the Tadoma method of speechreading. In this method, currently used by a small number of deaf—blind individuals, the receiver places his hand on the face and neck of the speaker and monitors various aspects of the articulatory process to understand speech. Our studies have involved one highly trained Tadoma user as well as several untrained, normal subjects. Experiments have been carried out to determine the general speechreading abilitites of the experienced Tadoma user, to compare performance of trained and untrained subjects on simple discrimination tasks, and to specify cues used in the perception of phonemes through Tadoma. Some results from these studies will be presented and discussed.
A striking demonstration of first-order spinning velocities in intense sound fields
Authors: Rudnick Isadore , Abbott James
Published: October 2005

The existence of first-order torques and solid body spinning velocities in intense sound fields has recently been established [T. J. Wang, H. Kanber, and I. Rudnick, J. Acoust. Soc. Am. 60, S53 (A) (1976); Phys. Rev. Lett. 38, 128 (1977)]. Because of its first order the effects are large and can be easily demonstrated in the classroom. An apparatus using the degenerate (2, 0, 0) and (0, 2, 0) (shifted 90° in phase) modes has been constructed which simultaneously spins four styrofoam cups at fairly high velocity at the four pressure nodes of the resulting sound field. As one expects the spin of neighboring cups have opposite signs. A novel feature of the design is that the mobility of the cups is greatly enhanced by the vibration of the floor of the enclosure which is driven by the sound field. A motion picture will be shown.
Diffuse-field sound pressure transformation to a manikin's ear, head surface, and torso surface
Authors: Kuhn George F.
Published: October 2005

The transformation of a diffuse sound pressure field to a manikin's ear, head surface, and torso surface was measured in a 425 m3 reverberation chamber between 0.2 and 10.0 kHz using 1/3-octave bandwidth random white noise. The maximum gain in sound pressure level at the microphone in an earlike coupler relative to the diffuse-field pressure was measured to be 15 dB at 2.7 kHz. Further measurements show that the pressure level buildup at the manikin's head surface and torso surface. when bare (acoustically hard), ranges from ∼0 dB at low frequencies to ∼+4 dB at high frequencies. Absorptive clothing reduces the pressure level buildup on the torso, where body-worn hearing aids or dosimeters may be located, to values ranging between −1/2 dB to +1 dB for frequencies ⩾1.6 kHz. Theoretical predictions of the diffuse field gain at the “eardrum” and head surface compare well with the experimental data.
Judgments of speech maturity: correlations with chronological age and acoustic measurements
Authors: Hawkins C. S. , Allen G. D.
Published: October 2005

An investigation of word-initial consonant cluster durations spoken by six children aged from 4 to 8 revealed only a weak association between maturity of production and chronological age (CA). This experiment was designed to see whether the children's speech maturity as judged by adults corresponded more closely to the instrumentally measured maturity of their consonant durations than either measure corresponded to CA. Elicited English monosyllables recorded during two periods one year apart were presented so that each child was paired with himself across the two years, and with other children within the same year. Using a definition of speech maturity emphasizing gestural integration and fluency, with less weight on phonemic adequacy and none on obviously age-related factors such as pitch and voice quality, 48 naive listeners judged which child of each pair spoke most maturely. Judgments of speech maturity correlated significantly both with predictions of the children's relative maturity derived from the similarity of their measured to adult norms, and with these predictions modified by impressions of the children's spontaneous speech. Neither the judgements nor the predictions correlated significantly with CA. Speech matured at very different rates for individual children, and actually decreased over the year for one.
Auditory perception, phonics and reading disabilities in children
Authors: Tallal Paula
Published: October 2005

In order to investigate the hypothesis that auditory perceptual disabilities may result in difficulty in learning phonics skills and hence in learning to read, reading impaired and normally developing children were given a battery of nonverbal auditory perceptual tests as well as a test of phonic skills. The auditory perceptual test battery examined (1) discrimination, (2) temporal order perception, (3) short-term memory, and (4) serial memory. Stimulus tones were presented at various rates. There were no significant differences between groups on any of the subtests in which stimuli were presented at slow rates. However, when the same stimuli were presented at slow rates. However, when the same stimuli were presented more rapidly, the reading impaired group made significantly more errors than the controls. The reading paired children's ability to use phonics skills (read nonsense words) was also examined. There was a high correlation between the number of errors made on the phonics reading test and the number of errors made in responding to the rapidly presented non-verbal stimuli in the auditory perceptual tests. The hypothesis, that some reading impairments are related to low level auditory perceptual dysfunction similar to that demonstrated previously for language impaired children, [P. Tallal and M. Piercy, Neuropsychologia 11, 389–398, 1973] is discussed.
Acoustic microscopy: Progress and applications, 1977
Authors: Kessler L. W.
Published: October 2005

In 1972 at the 84th meeting of ASA, a similarly titled review paper was presented by this author. Since that time, the field has progressed from very early beginnings and speculations to the point where there now appears to be some well-defined applications and advantages of the technique. In addition, a scanning laser acoustic microscope (SLAM) has become available commercially. Placed in the hands of biomedical and materials scientists, the SLAM becomes an important analytical tool for revealing aspects of microstructure which are not obtainable by optical or electron microscopes. In particular, the varying elastic properties of materials, e.g., compressibility and density, at the microscopic-size level are sensitive parameters upon which to differentiate structure. Applications of the SLAM to materials science, nondestructive testing, and biomedical research will be examined.