bluuebunny/crossref_metadata_2025 huggingface dataset:
Computer simulation of pathological vocal-cord vibration
Authors: Ishizaka K. , Isshiki N.
Published: October 2005

A dynamic model of the vocal cords, namely, a bilaterally symmetric two-mass model, is extended to a bilaterally asymmetric two-mass model to simulate pathological conditions of the vocal cords. Asymmetric behavior of the computer model is investigated for various conditions of imbalance in bilateral tension. The computer model is found to behave in three basic vibratory modes that are similar to those observed in physiological experiments on larynges under tension imbalance. The three distinctive modes are (1) a vibratory pattern with differences in phase and amplitude of cord vibration; (2) a nearly periodic motion without glottal closure; and (3) an unsteady, dicrotic or tricrotic motion. The three modes are found to be a strong function of the subglottal pressure and the glottal rest area, as well as the imbalance conditions of the cord parameters. The asymmetric vocal-cord model is incorporated into a dynamic vocal-tract synthesizer to simulate speech with a hoarse voice.

Subject Classification: [43]70.20, [43]70.50.
Array processors for simultaneous noise and interference suppression or simultaneous signal-to-noise and resolution enhancement
Authors: Glaser Gerald C. , Williams Ross E.
Published: October 2005

A symmetrical treatment is described of signal and interference arrivals, both spatially coherent across the aperture of a receiving array and appearing in a generalized ambient-noise background. By separating the coherent interference from the rest of the noise background, it is possible to implement a simple form of adaptive suppression of the interference, particularly when the latter is time varying and the remainder of the noise is stationary. Optimal processors are derived for simultaneous suppression of noise and interference, and for enhancement of the signal-to-noise ratio after elimination of interference. The processor for the latter case is shown to be a suboptimum version of the former. Both deterministic and stochastic interference are considered, as well as interference whose arrival time is synchronized with that of the desired signal (e.g., unwanted signal multipath arrivals, reverberation, etc.). Processors for two or more simultaneous and independent interference sources are described. Finally, the interference descriptor can be reinterpreted as a generalized resolution measure, so as to describe processors that simultaneously maximize the signal-to-noise ratio and the signal time resolution, or the signal-to-noise ratio and a combination of arrival angle and time resolution.

Subject Classification: [43]60.30.
Perceived roughness of amplitude-modulated tones and noise
Authors: Guirao Miguelina , Garavilla J. M.
Published: October 2005

Two sets of studies were conducted to determine the perceived auditory roughness of pure tones and narrow bands of noise modulated in amplitude. The signals used as carrier frequencies were 500- and 2000-Hz tones and two narrow bands of noise centered at the same two frequencies. Auditory roughness was measured by the psychophysical methods of magnitude estimation and a combination of magnitude estimation and magnitude production procedures. The average of the numerical estimates given by 10 Ss and the adjustments made by each one of the 40 Ss were plotted versus the degree of modulation m=Δ p/p of the SP. Results indicate that the perceived auditory roughness functions can be described by a power function with an average exponent of about 1.4. The exponent was about the same for the amplitude fluctuations of tones and noises.

Subject Classification: [43]65.75.
Temporal recognition masking—or interference?
Authors: Sparks David W.
Published: October 2005

Several experiments were performed in which brief tonal target bursts centered around 820 Hz were preceded and followed by interference signals. These interference signals included tones and noise bursts having a variety of durations, intensities, and center frequencies. Interference signals were ipsilateral or contralateral to the ear receiving the tonal targets. Backward recognition interference was observed with tonal maskers when target-masker frequency separations were within 10 Hz. No interference was observed with noise maskers. Aggregate results from these experiments suggest that disruptions in tonal recognition must occur after a preliminary perceptual analysis.

Subject Classification: [43]65.54, [43]65.75.
Temporal factors in vowel perception
Authors: Scott Brian L.
Published: October 2005

The perceptual role of the temporal fine-structure of vowel waveforms was investigated in five experiments. The interaction of the fundamental frequency and the first formant (F1) was shown to result in temporal  patterns  consisting of a number of cycles of F1 per fundamental frequency period. Changes in these  patterns  were shown to correlate with shifts in the perceptual boundary between /i/ and/I/. The results indicate that the perceptual system was responding to either a change in number of cycles of F1 per fundamental period or a change in the harmonic structure of the sounds. The hypothesized temporal cue was then used in synthesizing vowel- like sounds which, while not differing in formant center-frequency or harmonic structure, did differ in temporal structure. Subjects were able to match different sequences if the vowel-like sounds with sequences of natural vowels as predicted by their temporal properties. In a subsequent experi- ment, two pure tones were used as  building blocks  for synthesizing the vowels a, e, i, o, and u. With careful temporal modeling, the two tones proved sufficient fpr synthesizing intelligible tokens of the five vowels. Although the possibility exists that all the results may be explained in terms of spectrum, the indications are that temporal properties play a considerable role in vowel perception.

Subject Classification: [43]70.30; [43]65.75.
Discrimination of pure-tone intensities by the California sea lion
Authors: Moore Patrick W. B. , Schusterman Ronald J.
Published: October 2005

On the basis of previous behavorial experiments on sound localization under water along with sound–skull measurements in water, it was hypothesized that the California sea lion (Zalophus californianus) is capable of discriminating an intensity difference of approximately 3 dB at 16 kHz. The present experiment confirmed this hypothesis by means of a series of behavorial psychophysical experiments.

Subject Classification: [43]80.50, [43]80.60.
Physical optics farfield inverse scattering in the time domain
Authors: Bleistein Norman
Published: October 2005

The physical optics farfield inverse scattering (POFFIS) identity relates the phase- and range-normalized farfield backscattering amplitude to the spatial Fourier transform of the characteristic function of the scattering obstacle. The characteristic function is equal to unity in the region occupied by the obstacle and zero elsewhere. The original identity was derived by Bojarski for impulsive point sources. Here we extend the result to sources of arbitrary time dependence. We obtain an alternative form of Bojarski’s POFFIS identity. We also derive a POFFIS identity in the time domain. Numerically synthesized checks on the method are provided.

Subject Classification: [43]20.30.
Infrasonic sea noise at the Mid-Atlantic Ridge near 37°N
Authors: McGrath James R.
Published: October 2005

Infrasonic and low-frequency sonic sea noise was recorded for seven days in the 5- to 32-Hz band in the seismically active rift valley of the Mid-Atlantic Ridge near the Azores. Two ocean bottom seismographs (OBS) in water depths of about 2400 m made continuous, simultaneous recordings of acoustic and seismic signals generated by seaquakes. The dominant source of deep sea noise averaged over the recording interval was distant shipping traffic, deduced by comparing mean OBS levels to Wenz’s shipping noise estimates. Mean spectrum levels between 5 and 10 Hz did not exceed 80 dB//μPa, while mean levels at frequencies above 10 Hz were higher. The mean spectrum level at 5 Hz was about 9 dB lower than at 30 Hz, indicating that distant shipping traffic noise does not contribute to the noise field below 5 Hz. Radiated noise due to nearby ship passages comprised about 13% of the recording time and produced spectral lines at frequencies as low as 6.5 Hz. Over 515 seismic events were detected by one OBS unit; epicenters were estimated to be from 3 to 10 NM from the instrument. Seaquakes took place at a mean rate of 2.9 events/h, persisted from 12 sec to about 2 min, varied in Richter magnitude from 0 to 2.5, occurred as a swarn on at least one occasion and often raised broadband acoustic levels in excess of 20 dB.

Subject Classification: [43]30.70; [43]28.30.
Absorption of ultrasound in Freon-12
Authors: Jones H. W. , Stredulinsky D. , Vermeulen P. J.
Published: October 2005

Measurements of the absorption of sound in Freon-12 are reported for a range of f/p of 104–105 (Hz/atm). The data are shown in relation to similar data obtained at higher frequencies.

Subject Classification: [43]35.20.
Intelligibility of temporally interrupted speech with and without intervening noise
Authors: Powers Gerald L. , Wilcox Joseph C.
Published: October 2005

Experiments were performed to examine changes in the intelligibility of temporally interrupted sentences when white noise was introduced during the speech–free interval. In experiment 1, listeners received the test material under two conditions at five interruption rates ranging from 0.77 to 3.85 interruptions per second (ips). In one instance the speech-free interval was silent, while in the other it was switched to noise of the same average level as the speech. Experiment 2 examined the intelligibility of the speech message as a function of signal-to-noise (S/N) ratio. The switching rate was held constant at 1.5 ips and the S/N ratio was varied from −30 to +18 dB. Results indicated that for the particular interruption conditions selected, speech switched to noise is significantly more intelligible than speech interrupted by silence. In addition, intelligibility of the interrupted sentences in the presence of intervening noise varies with the S/N ratio.
Mathematical modeling of a probe-tube microphone
Authors: Egolf David P.
Published: October 2005

Mathematical modeling of acoustical systems is a popular design tool. To verify math models for acoustical systems of small physical size, probe-tube microphones are often used. Unfortunately, the presence of the probe tube, itself, sometimes affects the sound field being measured. One way to solve the problem is to account for this effect by incorporating a model of the probe tube into an overall math model of the entire system. Equations for analyzing sound transmission through probe tubes are not available in most contemporary acoustics textbooks. This paper describes a method for mathematically modeling the acoustical characteristics of probe-tube microphones using equations developed in 1950 for application to transient fluid flow in pipes. The accuracy of the method is demonstrated by mathematically simulating a probe-tube calibration experiment in the laboratory. The experimental data and data derived from the math model agree quite well over the frequency range from 10 to 10 000 Hz. This shows that the math model of the probe-tube microphone used in this experiment was correct. The result also suggests that this model may be included in an overall system model, given that several restrictions listed in this paper are closely followed.
Shallow-water propagation under downward-refraction conditions. II
Authors: Cohen Jeffrey S. , Cole Bernard F.
Published: October 2005

In May 1965, a comprehensive set of 3.5-kHz propagation-loss measurements was obtained under downward-refraction conditions in an area 40 NM south of Montauk, Long Island, New York. A technique for measuring bottom loss in shallow water, derived by taking advantage of the downward-refraction conditions, was applied to the test area. A bottom-loss value of 1.3 dB per bounce was inferred from the measurements and was shown to compare favorably with theoretical loss values generated using sediment information for the test area. As a result of that agreement, a computer model based on ray theory and bottom-impedance considerations was developed to describe shallow-water propagation in the test area (at least under downward-refraction conditions). To validate this model and further test the validity of the bottom-loss measurement, some additional measurements were conducted in the same test area during May 1967. This paper presents the propagation-loss results collected during the May 1967 measurements and compares them with those predicted by the model developed from the earlier set of measurements.
Limits to behavioral compensation for auditory localization in earmuff listening conditions
Authors: Russell Graeme
Published: October 2005

Two studies were carried out to examine how readily listeners adapt to earmuff impairment of auditory localization. In the first study 26 subjects were tested for localization accuracy with white-noise signals on each of three consecutive days. Even when subjects were given total feedback of their performance, they were still not able to completely adapt to earmuff listening. In the second study, two subjects were given two practice sessions per day on five days, for a simpler localization task. Again behavioral compensation did not occur. However, listeners were able to reliably distinguish between stimuli, but only using non-natural localization information. It was concluded that earmuffs produce a permanent loss of information that listeners cannot readily adapt to, and that as such, wearing earmuffs could be dangerous in some industrial settings.
Effect of a hollow spherical scatterer on the radiation resistance of a transducer at an air–water surface
Authors: Stumpf F. B. , Shukla S. S.
Published: October 2005

The radiation resistance of a small magnetostrictive sonar transducer at an air–water surface was measured in the presence of a hollow thin-walled plastic sphere immersed in the water. The sphere was placed on the radiation axis of the transducer and the transducer’s radiation resistance was measured as a function of the sphere’s depth in the water. The spherical scatterer has a measureable effect on the transducer radiation resistance when placed within a distance of approximately two wavelengths from the transducer.
Refraction of infrasound by upper-atmospheric winds
Authors: Georges T. M. , Beasley William H.
Published: October 2005

We used realistic models of upper-atmospheric winds in a three-dimensional acoustic ray-tracing program to calculate how much wind refraction alters acoustic transit speed and azimuth of arrival for long-distance paths. Transit speed varied by 20% or more, and bearing deviations of up to ten degrees were found, depending on the season and on the direction the waves travel. On the average, the predicted seasonal trends corresponded to osbervations, but the calculated standard deviations exceed the mean seasonal values, making simple corrections useless in individual cases. Furthermore, it is doubtful that variations of horizontally uniform winds alone can account for the large observed variability in refractive effects, specifically the large differences in bearing error at adjacent observatories. We show that realistic horizontal gradients of either temperature or wind could cause as much azimuthal refraction as our height-dependent wind models.
Application of cepstral techniques to ground-reflection effects in measured acoustic spectra
Authors: Miles Jeffrey H. , Stevens Grady H. , Leininger Gary G.
Published: October 2005

In acoustic measurements such as those conducted outdoors for static jet-engine noise research, aircraft-flyover noise certification, and motor-vehicle regulation, ground reflections create multipath conditions characterized by different signal arrival times which cause signal reinforcements and cancellations at the microphone. This generates undesirable effects on the measured spectra. Cepstral techniques, developed in speech processing to identify echo delay times, have been applied to the ground-reflection problem. Results indicate that cepstral techniques can produce a spectrum due to intensity addition only of the direct and reflected signals.
Array gain, correlation coefficients, and patch size
Authors: Nielsen Richard J.
Published: October 2005

An outline showing the equivalence of several common expressions for array gain is developed and the relationship between the various correlation coefficients and other parameters used to describe array gain is shown. The signal constraints under which the relationships are valid are indicated. Based on the model developed by Chernov, two experimental methods used to determine patch size are described. The relationships between the array gain parameters and model parameters are indicated and three sets of data collected south of Bermuda are compared.
Two-dimensional cochlear fluid model: New results
Authors: Allen J. B.
Published: October 2005

Many theories have been developed in past years which have attempted to model the function of the human cochlea. With the recent availability of the physical measurements of Rhode [J. Acoust. Soc. Am. 49, 1218 (1971)], these theories now appear to be inadequate. In this paper, improved numerical solutions have been found for the two-dimensional cochlear model proposed by Lesser and Berkley [J. Fluid Mech. 51,497 (1970)], using the Green’s-function method as first suggested by Cox and Lien [(1973) unpublished]. The Green’s-function method is used to derive an integral equation which may then be solved numerically. This procedure has proven to be stable, accurate, and faster than several other numerical solution techniques that have been tried. With an appropriate selection of the assumed membrane dissipation, the results are seen to agree within a few decibels of the Mössbauer measurements of Rhode, including the sharp change in slope observed in his amplitude ratio measurements just above the best frequency. This plateau occurs at a level which is 58 dB lower in amplitude than the amplitude at the best frequency.
Pitch of noise signals: Evidence for a ’’central spectrum’’
Authors: Bilsen Frans A.
Published: October 2005

A review is given of studies dealing with the pitch of signals derived from white Gaussian noise: the pitch of a (monotic) band of noise, the pitch of (dichotic) noise with an interaural phase shift, the monotic and dichotic repetition pitch, and the pitch of two interaurally delayed (uncorrelated) noises. The aim of the paper is to establish the relationship of these pitch phenomena and their connection with the pitch of monaurally presented simple tones (place pitch) and complex tones (periodicity pitch). Therefore, new experiments were performed on the pitch of two noise bands with harmonically related central frequencies, and the pitch of (dichotic) noise with interaural phase shifts at two harmonically related central frequencies, as well as the pitch of band-reject noise. A uniform explanation appears applicable, in correspondence with the theory of the pitch of complex tones, on the basis of the concept of a ’’central spectrum.’’ A simple schematic model of binaural interaction is used to describe the generation of the central spectrum. Pitch data can be accounted for by this model description. The existence region of pitch of dichotic signals is discussed in connection with other binaural functions, like lateralization, binaural beats, and binaural masked level differences.
Intensity discrimination as a function of frequency and sensation level
Authors: Jesteadt Walt , Wier Craig C. , Green David M.
Published: October 2005

Intensity discrimination was measured for pulsed sinusoids of various frequencies (200–8000 Hz) and sensation levels (5–80 dB). The data for all frequencies were fitted by a single function, ΔI/I=0.463 (I/I0)−0.072, where I0 is intensity at threshold, I is the intensity of the tone, and ΔI is the increment needed to obtain 71% correct in a two-interval forced-choice adaptive procedure. The form of this function is in good agreement with data reported in comparable studies but differs markedly from the data reported by Riesz [Phys. Rev. 31, 867–875 (1928)]. An analysis of the actual values of ΔI/I reported in the other studies indicates a range larger than would be predicted on the basis of individual differences among observers in this study. The data are also discussed differences among observers in this study. The data are also discussed in terms of the predictions of current theoretical models.
Comparison of sound-transmission and cochlear-microphonic characteristics in Mongolian gerbil and guinea pig
Authors: Schmiedt R. A. , Zwislocki J. J.
Published: October 2005

Characteristics of cochlear microphonic (CM) of guinea pigs, when compensated for electrical capacitive shunting within the cochlea, parallel corresponding mechanical characteristics. Specifically, good agreement is found for the middle-ear transfer characteristic, basilar-membrane phase, and cochlear travel times. CM corrections derived from guinea-pig experiments have been extrapolated to CM recorded in Mongolian gerbils to obtain estimates of middle-ear and basilar-membrane characteristics, a cochlear frequency map, and cochlear travel times for both animals. The estimates indicate that basilar-membrane tuning curves are almost symmetrical in the apical turn. Model experiments suggest that the apparent sharpening of the low-frequency leg of these curves is produced by a shunting effect of the helicotrema. Comparisons are also made among results obtained with three different electrode configurations: a single electrode in scala media (SM), a differential pair in scalae media and tympani (SM–ST), and a differential pair in scalae vestibuli and tympani (SV–ST). Results from both guinea pigs and gerbils indicate a slight advantage in the SM–ST configuration.
Measurement of sound absorption in rooms
Authors: Moreland J. B.
Published: October 2005

Existing methods for determining the sound absorption in rooms usually require some knowledge of the room dimensions. If sound-pressure-level measurements are made at various distances from a small source (such measurements herein referred to as a walk-away test) the room sound absorption can be deduced provided the variation of sound pressure level with distance can be described by the simple equation SPL=PWL (sound power level)+10 log10(Q/4πr2+4/A′), which is commonly credited to Beranek. Unlike the reverberation time and estimated area methods (𝒥Siαi), a walk-away test can be used to determine the room absorption where either the room volume or wall areas and the absorption coefficients are uncertain or for rooms which are acoustically coupled to other rooms.
Investigation of the surface acoustical intensity method for determining the noise sound power of a large machine i
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Authors: Hodgson Thomas H.
Published: October 2005

Measurements of the surface acoustical intensity have been made on a large centrifugal chiller in order to determine the major noise-radiating areas of the machine. In addition, an examination of the coherency of these major noise-radiating areas has suggested that the total noise power can be obtained by addition of the noise power outputs of each component. The measurements were limited to A-weighted sound-power levels. The feasibility of the method has been checked by calculating the radiation efficiencies of the two dominant noise radiators. The values were found to be consistent with current knowledge of sound radiation from flexural waves in plates. Similar calculations based only on nearfield pressure measurements have demonstrated the very complex nature of the pressure field surrounding this type of large machine in situ.
Cross-sensor beam forming with a sparse line array
Authors: Bucker Homer P.
Published: October 2005

By using the cross-sensor field, a beam pattern (for a one-wave, no-noise acoustic field) can be generated for a sparse array which is the same as for a filled array. When real-world effects, such as noise and multiwave acoustic fields, are considered, the performance of the sparse array degrades more than the preformance of the filled array. However, by time averaging the cross-sensor field the performance of the sparse array is noticeably improved.
Implementation and validation of a model for surface reverberation
Authors: Higgins Robert C. , Francis James T. , Hoy Ronald W.
Published: October 2005

A model for narrow-band surface reverberation is formulated, implemented on a general-purpose computer, and validated. At each instant of time, the model divides the ocean surface into an annulus of incremental sectors. The time and frequency characteristics of the reverberation from each sector are modeled by passing Gaussian random noise through narrow-band digital filters. Spherical spreading, absorption, and nonisovelocity effects are included in the model. The validation is accomplished by statistically comparing the model’s output with experimental data collected in an open-water environment.
Spatial differentiation as an auditory ’’second filter’’: Assessment on a nonlinear model of the basilar membrane
Authors: Hall J. L.
Published: October 2005

The mechanical tuning of the basilar membrane does not appear to be sharp enough to account for frequency selectivity of primary auditory-nerve fibers. Various ’’second filters’’ have been proposed to provide the required sharpening. We have studied the properties of one such mechanism, in which the spatial derivative of membrane displacement is taken as the excitatory signal for primary fibers, on a nonlinear computational model of the basilar membrance. Because the wavelength in response to a tone decreases as the wave travels from base to characteristic place, both the slope and curvature of membrane response are enhanced in the neighborhood of the characteristic place. Thus spatial differentiation produces sharpening resembling the difference between mechanical and neural tuning. Phase (as a function of frequency) of the spatial derivative is similar to phase of the displacement, but frequency selectivity (amplitude as a function of frequency) for frequencies below the characteristic frequency is sharpened. In addition, spatial differentiation provides the distinction between mechanical nonlinearity (related in the model to membrane velocity) and neural excitatory signal required to account for suppression of response to a tone at the characteristic frequency f1 by a second tone at a lower frequency f2. Without this distinction, a tone at frequency f2 intense enough to suppress the f1 component of response at the f1 place would itself introduce a large component of response at frequency f2.
Detection of temporal gaps in noise as a measure of the decay of auditory sensation
Authors: Penner M. J.
Published: October 2005

The masking of silent intervals, or gaps, by surrounding noise bursts was investigated. The durations and the spectrum levels of the two noises were varied and the just detectable gap ΔT determined. The first experiment demonstrated the conditions in which duration judgments may have provided a cue. The remaining experiments were therefore designed so that this duration cue was not available. The second experiment indicated that changing the second noise duration from 200 to 2 msec did not greatly affect ΔT, suggesting a close relationship between forward masking and gap detection. Finally, Plomp [J. Acoust. Soc. Am. 36, 277–282 (1964)] has argued that a graph of the level of the second noise in decibels as a function of log ΔT traces the time course of decay of the first noise. If so, the data from the third experiment indicate that this decay rate depends on the spectrum level of the noise but not on its duration.
Threshold shift in the chinchilla from daily exposure to noise for six hours
Authors: Saunders James C. , Mills John H. , Miller James D.
Published: October 2005

Trained chinchillas were exposed to 6 h of noise followed by 18 h of quiet for nine days. Thresholds (0.5–8.0 kHz) were measured immediately before and after each day’s exposure. The decay of threshold shift after the ninth day was followed until stable thresholds were again observed. This procedure was repeated for six levels (57–92 dB SPL) of an octave-band noise centered at 4.0 kHz. The threshold shift measured after 4 min of quiet (TS4) appears to reach an asymptotic level (ATS4) after the first or second exposure. ATS4, measured at frequencies exhibiting greatest shift (5.7 kHz), increases with the level of the noise with the same slope (1.7 dB/dB) for the daily 6-h exposures as for nearly continuous exposures. ATS4 is smaller for 6 h than nearly continuous exposures by about 5 dB and this difference can be explained by an equivalent-power hypothesis. The decay of threshold shift was nearly complete after 18 h of quiet for the lowest levels of noise, while it was nearly complete only after 3–5 days for the intermediate levels of noise. The decay of threshold shift was never complete and small amounts of permanent threshold shift were observed for the highest levels of noise.
Low-frequency masking patterns
Authors: Tobias Jerry V.
Published: October 2005

Tones below 500 Hz show masking effects that are different from those of higher-frequency tones. Where middle- and high-frequency tones have their maximum effect at the masking frequency, and most of the rest of their effect at frequencies higher than themselves, low-frequency tones are consistently most effective in the 400- to 600-Hz range. Possible explanations are offered.
Auditory reaction time and absolute threshold in cat
Authors: Gerken George M. , Sandlin Dick
Published: October 2005

Reaction time and absolute thresholds for acoustic stimuli were measured in cats using an operant reaction-time procedure in conjunction with titration methodology. The reaction-time/titration procedure incorporated a self-paced feature and utilized a photobeam operandum developed for the cat. Absolute auditory thresholds, measured in two animals for frequencies between 0.25 and 8.0 kHz, compared favorably with published threshold data for the cat. Both threshold and reaction time were influenced by the test and stimulus conditions. A method of estimating the effect of guessing was developed that eliminates the need for catch trials. The reaction-time/titration threshold procedure appears to be an effective method for use with the cat.
Time-intensity trades revisited
Authors: Young Lamar L. , Levine Judith
Published: October 2005

Two experiments were accomplished which involved time-intensity trades on a lateralization task. In the first experiment, subjects adjusted interaural time differences between binaural stimuli to compensate for interaural intensity disparities. In the second, the same listeners adjusted the interaural intensity relationship to offset interaural time differences. Three pure tones (250, 500, and 1000 Hz) were employed as binaural stimuli. The two experiments yielded substantially different time-intensity trading ratios for large values of interaural time differences and intensity disparities. This finding supplies evidence of a new type that the time-intensity trading ratio does not accurately reflect the central auditory processes that are involved with interaural time and intensity on a lateralization task.
Acoustic reflection from layered elastic absorptive cylinders
Authors: Flax Lawrence , Neubauer Werner G.
Published: October 2005

The reflection of plane waves by a layered cylindrical shell in water is investigated theoretically. Either or both of the two layers of elastic material may be absorptive. The solution as a function of frequency is examined for several combinations of inner and outer layers.
Vertical side-lobe suppression in cylindrical arrays
Authors: Rolleigh Richard L. , Pruitt James G. , Stokes Robert H.
Published: October 2005

The vertical side-lobe structure of cylindrical arrays driven in phase is examined. Experimental results demonstrate that the vertical side-lobe levels are significant when the angular aperture of the array is large. The physical cause of this phenomenon is identified, and a method of eliminating excessive side-lobe levels is explained. Experimental results showing that this method is successful are presented.
Introduction to session on the noise of large machines St. Louis, Missouri, 6 November 1974
Authors: Angevine O. L.
Published: October 2005

This is a special joint session sponsored by the Technical Committees on Noise and on Architectural Acoustics. There were six invited papers.
Notes on the forward-scatter approximation
Authors: Wenzel Alan R.
Published: October 2005

An asymptotic expansion in inverse powers of the wave number is derived for an integral of a type often encountered in the theory of wave propagation in inhomogeneous media. The procedure, which is essentially a forward-scatter approximation, yields all the terms of the expansion. In contrast, the conventional forward-scatter approximation is found to yield correctly only the first term of the expansion.
Relation between creeping waves and normal modes of vibration of a curved body
Authors: Überall H. , Dragonette L. R. , Flax L.
Published: October 2005

The natural way for a disturbance to propagate over the surface of a smoothly curved, fluid-loaded elastic body is in the form of a series of damped circumferential (creeping) waves. Mathematically, the process is most conveniently described by a sum of normal modes, each characterized by a wavelength that fits the body’s circumference an integer number of times. We demonstrate that any given mode will resonate at a multiplicity of ’’eigenfrequencies,’’ determined by the speed of any one of the creeping waves matching the mode velocity. For an elastic cylinder, the 180° sound-scattering amplitude is seen to possess marked minima at many of the eigenfrequencies, which are shown to be generated successively by a single circumferential wave, and whose spacing in this sequence determines the group velocities of circumferential pulsed signals.
Focusing conditions for sonic booms
Authors: Dempsey Daniel F.
Published: October 2005

A pair of sonic-boom focusing conditions is obtained which holds for accelerated circular or linear flight in a uniform atmosphere. A geometric interpretation follows, the one focusing condition being represented by a cone while the other is represented by a plane. Points of intersection of these two surfaces are points of focus. Details are worked out for steady circular flight and it is seen that focal points at lower levels travel in horizontal circular paths whose size keeps increasing as lower and lower levels are considered. For accelerated linear motion the focusing conditions lead to a surface of focusing points which can be expressed in a form general enough to represent all values of acceleration, and whose shape is a surface of revolution generated by revolving a semicubical parabola about the flight axis. Cases of extreme focusing are also considered, one for accelerated linear flight and one for curved flight at constant speed.
Estimation and interpretation of acoustic cw phase fluctuation spectra
Authors: Adams Stanley L. , Jobst William J.
Published: October 2005

A fundamental question exists regarding how well information about ocean processes can be extracted from a time series of cw acoustic phase and amplitude when the propagation channel consists of multiple acoustic paths. In this paper, it is shown that there are at least two multipath propagation conditions under which an acoustic cw propagation experiment can be used to measure properties of the sound-speed field and the ocean processes along the propagation path: narrow-band (frequency-modulation) path-length modulation of all paths, and wide-band (frequency-modulation) path-length modulation of a dominant path. A dominant path is one with power which exceeds the power on all other paths plus noise by at least 6 dB. Signal processing techniques for measuring the fluctuation spectra in both multipath situations are described and performance estimates are derived. The factors which limit how well information can be extracted are discussed.
Modulation of acoustic phase by internal-wave vertical velocity
Authors: Jobst W. , Clark J.
Published: October 2005

Relationships are developed between internal-wave vertical velocity and acoustic phase. For source–receiver separations of many internal-wave wavelengths, it is shown that the mapping of internal-wave energy onto the phase of a single acoustic path is highly directional. Internal waves propagating perpendicular to the acoustic path produce the greatest phase modulation, and modulation of acoustic phase is reduced in all other geometries. For the omnidirectional internal-wave spectrum proposed by Garrett and Munk, the acoustic phase-modulation power spectrum is proportional to ω−3 and j−3, where ω is the internal-wave radian frequency and j is the internal-wave vertical-mode number. The first-mode internal wave contributes more than half of the acoustic phase-modulation power, and in this sense, the first-mode internal wave dominates the acoustic phase spectrum.
Impact response of a layered composite containing a crack
Authors: Chen E. P.
Published: October 2005

The impact response of a crack in a layered composite which is subjected to antiplane shear deformation is considered in this study. The geometry of the composite consists of a finite layer that is sandwiched between two half-planes made of a different material. The finite layer contains a central crack which is oriented normally to the interfaces. Laplace and Fourier transforms are used to reduce the problem to a pair of dual integral equations. The solution to the dual integral equation is expressed in terms of a Fredholm integral equation of the second kind. Dynamic stress intensity factor is obtained as a function of the material properties, the geometry parameters, and time. It is found that the amplitude of the local stresses reaches a peak very quickly and then decreases in amplitude oscillating about the corresponding static value. Depending on the stiffness ratio between the materials, this peak value can be either higher or lower than the value for a homogeneous isotropic material.
Efficient computation of array patterns
Authors: Anderson V. C.
Published: October 2005

The impact of a symmetrical array geometry, the use of a quantized stored cosine function, the exploitation of digital Fourier transform algorithms, and the application of trigonometric interpolation in the computation of array patterns is discussed. Careful selection of parameters permits sampling the array pattern only 6% above the theoretical Nyquist limit. Reconstruction of array patterns showing −20, −30, and −40-dB relative interpolation errors are presented. A saving of 8000:1 in computation time over direct ’’brute-force’’ array-pattern computation is illustrated for a hypothetical array.
Effects of crossed olivocochlear bundle stimulation on the cochlear summating potential
Authors: Gans Donald P.
Published: October 2005

The crossed olivocochlear bundle (COCB) was stimulated with biphasic pulse trains while recording the cochlear summating potential (SP) with electrodes placed in scala vestibuli and tympani of either the first, second, or third cochlear turns of 21 guinea pigs. The outputs of the two electrodes were subsequently added (AVE SP) and subtracted (DIF SP) so that various components of the SP could be analyzed. It is shown that the DIF SP was consistently altered in a positive direction in all three cochlear turns at all frequencies and intensities during efferent activation. The greatest relative COCB effect for the DIF SP was achieved when it was recorded at low intensities and from the second and third turns of the cochlea. Both AVE SP components were significantly decreased in magnitude when recorded from the first turn during COCB stimulation. Data collected from turns two and three suggested that the efferent system exerts a strong positive influence on the overall AVE SP response. The results suggest that the efferent influences on the SP are consistent with models of COCB action on hair cells. Further, the findings conform to what would be predicted by other biasing techniques, and therefore it is recommended that COCB stimulation be considered as a tool for studying the origin and function of the cochlear potentials.
Sonar velocity resolution with a linear-period-modulated pulse
Authors: Altes R. A. , Skinner D. P.
Published: October 2005

For linear-period-modulated (LPM) signals, the phase of the echo from a moving-point target contains information about range rate. When an LPM signal is transmitted, a Doppler-insensitive sonar processor is obtained by following a matched filter with an envelope detector. Velocity information can be extracted from the same echo, however, if the receiver is sensitive to phase. A receiver that envelope detects matched-filter responses and also estimates the phase of an echo can therefore be both Doppler tolerant and Doppler resolvent. If LPM is used, only two matched filters are needed to implement a sequence of M velocity hypotheses, rather than a bank of M different filters. LPM is thus an excellent signal format not only for Doppler-invariant range estimation and initial detection, but also for fine velocity resolution with minimum receiver complexity. The existence of velocity-induced phase transformations in LPM signals also leads to a new synthetic aperture sonar technique.
Minimum differences of level and frequency for perceptual fission of tone sequences ABAB
Authors: van Noorden Leon P. A. S.
Published: October 2005

Stream segregation or fission of the fast alternating tone sequence ABAB is known to occur if there is a sufficient frequency difference between the tones A and B. In this paper it will be shown that level difference instead of frequency difference can be sufficient to enable the occurrence of fission. The smallest level difference between A and B, ΔL?3 dB (2.5–10 tones per sec; tone duration 40 msec). At rates faster than 12 tones per sec a new perceptive phenomenon was observed: the roll effect. It is characterized by the weak tones being heard at double the tempo. The relation with the continuity effect is investigated using alternating sequences with both level and frequency difference between the tones as stimuli.
Low-frequency acoustic fluctuations and internal gravity waves in the ocean
Authors: Porter R. P. , Spindel R. C.
Published: October 2005

Acoustic phase and amplitude fluctuations measured during two experiments, one near Eleuthera Island and one near Bermuda, are presented and interpreted in terms of the interaction of sound with internal gravity waves. Data were collected with a variety of sensors including drifting ship-suspended hydrophones, sonobuoys (free-floating acoustic receivers equipped with a UHF transmitter for data communication), and moored hydrophones. The phase data were corrected for hydrophone motion by means of a bottom-moored Doppler navigation system. Oceanographic data are presented and compared with the acoustic data; these data comparisons show that internal waves are responsible for much of the acoustic fluctuations. Phase spectra obtained with moored hydrophones show a rapid spectral decay at frequencies above the highest osberved Brunt–Vaisala frequency as predicted by internal-wave–acoustic models. Spectra obtained with drifting hydrophones are compared with a recently proposed random, multipath model based on interaction of sound with internal waves. Spectra obtained for drifting hydrophones at a depth of 1500 m agree with the multipath-model prediction. Spectra from phones at shallower depths exhibit an order of magnitude more fluctuation energy than is predicted. Slowly drifting sonobuoys at a depth of 300 m produce spectra with a complex frequency dependence that can not be predicted by the random multipath model.
Surface waves of an elastic medium in the presence of an inviscid flow field
Authors: Pierucci Mauro
Published: October 2005

The stability of an elastic layer being excited by a flow field is examined. The dynamics of the elastic layer is assumed to be governed by the basic elasticity equations. On the lower surface the layer is assumed to be fixed to a rigid surface. On the upper surface, a potential flow field is assumed to provide the exciting force. A solution to the linearized set of elasticity and fluid-mechanics equation is obtained. When all of the boundary conditions are satisfied, a compatibility equation is obtained. Complex and real eigenvalues of this equation for different Poisson’s ratio, Young’s modulus, and flow velocity have been obtained. In the limit as the fluid density goes to zero the classical Rayleigh surface waves are recovered.
Reflection and refraction of transient waves in fluid-filled porous media
Authors: McNiven Hugh D. , Mengi Yalcin
Published: October 2005

In this study, reflection and refraction of transient waves in a nonhomogeneous fluid-filled porous body is investigated. The body involves a layer of one porous material perfectly bonded to a half- space of another porous material. Transient waves are generated at the top surface of the layer by a time-dependent applied pressure. For a variety of material properties chosen for the layer and half-space, the time variations of various physical quantities are found at two stations: one in the layer, the other in the half-space. A study of numerical results, obtained by the method of characteristics, indicates that the rigidity of the half-space relative to that of layer strongly affects the reflection and refraction characteristics of transient waves with regard to sign while the relative permeability of the half-space has an influence on their dispersive characteristics.
Hierarchy of masking-level differences obtained for temporal masking
Authors: Yost William A. , Walton Joseph
Published: October 2005

Masked thresholds were obtained in four binaural conditions (N0S0, N0Sm, NπS0, and N0Sπ) and in four temporal-masking conditions (simultaneous masking, forward masking, backward masking, and combined forward–backward masking). In all conditions Gaussian noise was the masker and was low-pass filtered at 5000 Hz and presented at 43-dB spectrum level. The signal was a 20-msec, 500-Hz tone gated with a 5-msec rise-decay time. The temporal interval between signal offset and masker onset (masker duration 500 msec) in the backward-masking condition was 1 msec. The temporal interval between masker offset and signal onset was 10 msec in the forward-masking condition. These same temporal intervals (but 250-msec maskers) were used in the combined forward–backward masking condition. The hierarcy of masking-level differences (MLD’s) was the same in all of the temporal-masking procedures and matched that obtained in the simultaneous masking condition. More additional masking was obtained in the combined forward–backward masking condition for the N0S0 condition than for any of the binaural conditions (N0Sm, NπS0, and N0Sπ).
Preliminary study of a low-frequency, formant-based speech code for the severely hearing impaired
Authors: Reeder Kaye , Strong William J. , Palmer E. Paul
Published: October 2005

This correspondence describes a computer-derived low-frequency auditory speech code. The code employs only three low-frequency tones consisting of sine waves, or narrow-band noise, plus overall amplitude control. The frequencies of the tones are a function of the three highest-amplitude formants in the speech signal.. A report of preliminary tests of the ability of normal-hearing and hearing-impaired subjects to learn common words and to discriminate words of a diagnostic rhyme test is given.