bluuebunny/crossref_metadata_2025 huggingface dataset:
Tympanic-Membrane Vibrations in Human Cadaver Ears Studied by Time-Averaged Holography
Authors: Tonndorf Juergen , Khanna Shyam M.
Published: October 2005

Tympanic-membrane (TM) vibrations were studied in fresh human-cadaver specimens by means of time-averaged holography. As with an earlier study in cats [S. M. Khanna and J. Tonndorf, J. Acoust. Soc. Amer. 51, 1904 (1972)], the findings supported the curved-membrane hypothesis of Helmholtz. Despite a careful search for experimental artifacts, no satisfactory explanation was found to account for the fact that the present results are at variance with the stiff-plate concept of von Békésy. With respect to their quantitative evaluation, the human-cadaver data were not as clear-cut as the earlier cat data on account of anatomical differences. A number of points, which on first glance do not seem to agree with Helmholtz's concept are being discussed in the light of present or other recent findings, and explanations are being offered. These topics include: (1) the compliance of the TM; (2) the effects of differential air pressure across the TM upon middle-ear transmission; (3) the effects of TM perforations; and (4) the fact that Helmholtz's cadaver experiment, which was thought to support his hypothesis, could not be duplicated.
Multivariate Analysis of Subjective and Physical Measures of Hall Acoustics
Authors: Yamaguchi Kiminori
Published: October 2005

The purpose of this study is (1) to examine whether the differences of sound-field qualities among seats in a music hall are accountable by a kind of multivariate procedure, (2) to examine whether subjective characteristics of several music halls are comparable with this technique, and (3) to propose a new method to estimate sound-field characteristics of music halls from physical terms, in place of words used in conventional techniques. Experimental procedures: (1) First, program sources are recorded in an anechoic room, and those sources are reproduced through a omnidirectional loudspeaker system on the stage of a music hall, Yamaha Music Camp. Those reproduced sounds are recorded stereophonically at each seat. (2) Then the hearing tests for those reproduced sources are carried out with dynamic receivers in a sound-proof room. (3) At the same time acoustic characteristics of the room such as percent-articulation, directional diffusivity, definition, reverberation time, transmission characteristics, SPL variation, etc., at the respective seat are measured. Subjective characteristics were first analyzed by multidimensional scaling (MDS), which yielded three orthogonal factors. Then, principal axis method (PAM) was applied to the correlation matrix of these factors and the physical measurements. The results were that three factors were extracted by PAM; the first represents SPL level, the second reverberation time or definition, while the third is not interpreted. An interpretation of these subjective characteristics in terms of physical measurements is proposed.
Greenspan Rule for Combined Absorption of Sound in Polyatomic Gases with Many Internal Degrees of Freedom
Authors: McCormack Francis J.
Published: October 2005

The Greenspan rule for calculating the combined absorption of sound in polyatomic gases from the separate values of the classical and internal absorption is extended to include the effects of more than one internal degree of freedom. Comparison is made between the results of absorption calculations based on this generalization and those obtained from the simple addition rule and the 17-moment theory.
Acoustic-Doppler-Radar Scattering Equation and General Solution
Authors: Brown Edmund H.
Published: October 2005

The basic equation for propagation of sound-wave pulses through a turbulent atmosphere moving with a mean wind has been obtained from first principles. The general solution of the basic equation has been found and expressed in a form simple enough to permit application to the analysis of problems of prediction and interpretation of data obtained from the various types of acoustic sounder experiments, including power spectra, intensity spectra, and cross sections for both backscatter and forward-scatter configurations.
Speed of Sound in Pure Water
Authors: Del Grosso V. A. , Mader C. W.
Published: October 2005

A sound-speed equation of fifth order in temperature is fit with a standard deviation of 0.0028 m/sec to 148 observations between 0.001°C and 95.126°C on the T68 scale. The accuracy is believed to be 0.015 m/sec, and the reproducibility over replications is 0.005 m/sec.
On the Calculation of Ray-Acoustic Intensity
Authors: MacKinnon Robert F. , Partridge John S. , Toole S. H.
Published: October 2005

A procedure is described by which ray-acoustic intensity due to a point source in a horizontally uniform medium can be calculated with a digital computer. The process includes a curve-fitting technique applied to velocity-of-sound data, the numerical integration of two sets of two simultaneous ordinary differential equations, the imposition of boundary conditions at reflecting surfaces, and the application of recurrence relationships relating partial derivatives within the first ray path cycle to those at ranges beyond the first cycle. For media with horizontal boundaries it is shown how the required numerical integration can be reduced greatly through use of the symmetries of the ray path. It is shown that significant errors can be introduced to the numerical process through discontinuities in derivatives of the sound-velocity profile. Consideration is given to the propagation of such errors. The error-propagating characteristics of recurrence relationships for intensity are considered also. A curve-fitting technique is described which ensures continuity of the third derivative of the sound velocity and which produces profiles without the extraneous undulations so often introduced by other procedures. It is demonstrated how intensity can be affected greatly by small changes in the sound-velocity profile.
Discrimination of Interaural Time and Intensity
Authors: Gilliom John D. , Sorkin Robert D.
Published: October 2005

Discrimination tasks with a 500-Hz tone and involving various combinations of binaural time and intensity cues were used to generate binaural discrimination spaces. The resultant spaces indicate that the sensations which arise from interaural time cues and interaural amplitude cues are correlated with a correlation coefficient of approximately 0.88; that is, a large fraction of the total sensation arising from one interaural cue will add or subtract as a scalar quantity with the sensation produced by the other interaural cue, but a residual sensation will always remain for all combinations of time and intensity cues. The same spatial framework provides a good description of the results of time intensity trading tasks. When applied to an MLD detection paradigm, this framework provides predictions which are in qualitative agreement with masking studies using tones and narrow-band noise as maskers.
Some curious analytical ray paths for some interesting velocity profiles in geometrical acoustics
Authors: Barnes A. , Solomon L. P.
Published: October 2005

Geometrical acoustics problems in oceanic applications are solved using complicated computer codes. This paper presents some cases which may be used to verify these codes. The velocity profiles are depth dependent, range dependent, and depth and range dependent. The ray path solutions, as well as the velocity profiles, are all expressed in terms of analytical, closed form, or at worst, tabulated functions.
Response of the impact damper to stationary random excitation
Authors: Masri S. F. , Ibrahim A. M.
Published: October 2005

The response of an impact damper system to an excitation with approximately white-power spectral density and Gaussian probability distribution is determined, using two independent methods: digital computer and electronic-analog techniques. Results are given for mean-squared level, power spectral density, probability density, probability distribution, and amplitude probability density of the response. The impact damper is found to be a practical and efficient device for reducing the response amplitude of systems subjected to random excitation.
The bowed string and the player
Authors: Schelleng John C.
Published: October 2005

Relations between bowing parameters, i.e., force applied, bow position, and velocity, are derived in terms of load impedance presented by bridge to string, characteristic impedance, and frictional coefficients. The range between least applied force needed to couple bow to load during sticking and maximum permitting uncoupling following sticking provides the generous tolerance, variable but typically in the ratio of 1 to 10, that makes the bowed string so flexible in performance. Domains of string behavior recognized by players are related graphically to bowing parameters. An electromagnetic method for observing particle velocity in the string reveals small but significant ripples caused by forces at the bow that the idealized explanation ignores. In one very flexible string, force exerted on the bridge varied approximately inversely with frequency out to the 15th harmonic, whereas for a string equivalent to a gut G for violin force became zero near the 7th. Elastic effects are considered, and it is suggested that in strings, either solid or wound, inharmonicity of 0.1 cent per square of mode number will not perceptibly degrade bowed-string performance.
Discrimination of fundamental frequency contours in synthetic speech: implications for models of pitch perception
Authors: Klatt Dennis H.
Published: October 2005

The just-noticeable difference (JND) for selected aspects of voice fundamental frequency (F0) contours was determined by varying the F0 control parameter of a digitally simulated terminal analog speech synthesizer. Data were obtained from three subjects for a number of 250-msec segments of the synthetic vowel /ɛ/ differing only in fundamental frequency. Results indicate that the subjects can detect a change of 0.3 Hz in a constant F0 contour when F0 = 120 Hz, but the JND is an order of magnitude larger (2.0 Hz) when the F0 contour is a linear descending ramp (32 Hz/sec). Sensitivity to rate of change of F0 in linear ramps is surprisingly good; greatest sensitivity occurs when one ramp increases and the other decreases (JND = 12 Hz/sec). High-pass filtering of the stimuli improves performance slightly, suggesting that the fundamental component is not involved in the detection of changes in F0. Substitution of the synthetic stimulus /ya/ with its dynamic formant contours in place of /ɛ/ degrades performance only very slightly. Implications of these data for models of pitch perception mechanisms are discussed.
Acuity of the human sound localization response underwater
Authors: Feinstein Stephen H.
Published: October 2005

Minimum Audible Angles (MMA) for divers were determined for 3.5 kHz, 6.5 kHz, and broad-band white-noise pulses having a duration of 100 msec, a rise-decay time of 10 sec, and a repetition rate of 1/sec. In Expt. 1 six divers performed the right-left discrimination with no training or feedback and the mean MAAs obtained were 21.5° for the 3.5-kHz signal, 14.5° for the 6.5-kHz signal, and 9.8° for the white-noise signal. In Expt. 2 four of the original six divers were given feedback from their performance with the white-noise signal at a single small angle. The mean MAAs obtained after training were 11.3° at 3.5 kHz, 11.5° at 6.5 kHz, and 7.3° with white noise. It was concluded that if one assumes that the MAA reflects the general level at which the binaural system operates then it seems likely that man will be an effective sound navigator in the water.
Multidimensional coding within the temporal microstructure of auditory displays
Authors: Pollack Irwin
Published: October 2005

The feasibility of encoding multivariate information within the temporal microstructure of an auditory display is examined. Four pulse variables—ear of arrival, polarity, amplitude, and interpulse interval—were independently encoded pulse-by-pulse within auditory pulse trains. A fifth variable—conditional memory, representing the previous state of one of the variables—also served as an independent variable in combination with other variables. An informational constraint of up to 1 bit/pulse was imposed upon the combination of variables. Each variable was binary coded and constraints were imposed upon the combination of variables by means of a parity sum across variables. The accuracy of discrimination of a constant informational constraint falls with the number of variables contributing to the parity sum, and with the number of randomly manipulated variables outside of the parity sum. Excellent discrimination of the informational constraint was achieved for one condition with four independently controlled variables. Specific contributions of pulse variables were strikingly more discriminable than others.
An integrable model for the basilar membrane
Authors: Schroeder M. R.
Published: October 2005

Assuming a logarithmic relationship between place and characteristic frequency, proportionality between the latter and phase velocity, and a loss factor independent of place, the wave equation for the basilar membrane displacement can be integrated analytically. The main theoretical results are as follows: (1) The low-frequency phase slope equals approximately −Kωr(x), where K is a dimensionless constant and ωr(x) is the characteristic frequency at place x; (2) the asymptotic high-frequency amplitude slope equals −6(K+1) dB/oct; (3) just above resonance the phase reaches a minimum value of about −K rad. The Rhode (1971) low-frequency phase-slope data yields K=27±3. The asymptotic high-frequency amplitude slope should therefore be (168±18) dB/oct. Surprisingly, the great frequency selectivity of the cochlea as reflected in the large numerical value of the high-frequency amplitude-slope is not determined by hydromechanical losses, which primarily influence behavior, near resonance, but the constant K whose physical meaning is approximately “2π times the number of wavelengths” on the membrane for low frequencies. With the above value for K, the number of wavelengths becomes about five—considerably more than found by von Békésy. Nevertheless, it is interesting to note that the phase slopes and high-frequency amplitude slopes of von Békésy (1960, pp. 446–463) are not inconsistent the light of the present theoretical calculations. If the membrane becomes stiffer at the high amplitudes at which von Békésy made his measurement, both phase and amplitude slopes would be decreased.
Threshold adaptation in normal listeners
Authors: Snyder Jack M.
Published: October 2005

Threshold adaptation for 500, 1000, 2000, and 4000 Hz was studied with the Carhart, Rosenberg, and Owens tone decay tests using 40 normal-hearing subjects. Differences in tone decay were evaluated for effects of experimental technique, frequency, hearing level and SPL of the stimuli. There were no significant differences between the results obtained with the three experimental conditions. Appreciable differences in the amount of decay (10 dB or greater) were shown only for 4000 Hz in terms of mean decay. Appreciable amounts of decay (to 25 dB) were found for 1000, 2000, and 4000 Hz in terms of individual test results. All frequency comparisons displayed significantly different ranking at the 0.05 level of confidence. As frequency increased in hertz, tone decay increased in decibels. Effects of hearing level and SPL of the stimuli were without statistical significance.
Velocity-dependent reflection, refraction, and scattering of elastic shear waves in the presence of a lubricating layer
Authors: Schoenberg Michael , Censor Dan
Published: October 2005

Wave-scattering problems involving moving media should take into account the effect of the boundary layers at the sliding interfaces. A recent paper by Graham and Graham [J. Acoust. Soc. Amer. 46, 169–175 (1969)], although restricted to acoustical waves, is indicative of the difficulties involved. Presently we consider shear waves in moving elastic media, having a viscous (Newtonian) fluid layer separating the sliding interfaces. The mean velocity profile in the viscous medium is prescribed by the solution of the relevant Navier-Stokes equation and is unaffected by the perturbations. For the mean velocity profiles encountered between parallel planes and between concentric cylinders, solutions for shear waves are obtained in terms of Bessel functions. Various limiting cases are investigated.
Propagation in time-dependent ideal channels: application to Straits of Florida studies
Authors: Clark John G. , Yarnall James R.
Published: October 2005

Current letters by M. J. Jacobson, D. T. Raphael, and J. T. Warfield have reviewed recent developments in the ray theory of propagation in “ideal ocean channels” [J. Acoust. Soc. Amer. 49, 1679–1680(L) (1971); J. Acoust. Soc. Amer. 49, 1680–1681(L) (1971); J. Acoust. Soc. Amer. 51, 1111–1112(L) (1972)]. The purpose of this paper is to describe related studies of propagation in “time-dependent, ideal channels” and to show how results of these studies compare with experimental measurements in the Straits of Florida.
Another search for anomalies in the temperature dependence of the speed of sound in pure water
Authors: Del Grosso V. A. , Mader C. W.
Published: October 2005

Over 1000 relative measurements of the speed of sound in pure water between 0° and 10°C contribute nothing additional to the earlier indication [V. A. Del Grosso and C. W. Mader, J. Acoust. Soc. Amer. 52, 1442–1446 (1972)] that there is no anomaly larger than 2 ppm.
Layered oceanic microstructure—its effect on sound propagation
Authors: Mellberg Leonard E. , Johannessen Ola M.
Published: October 2005

It has recently been established that the vertical profiles of oceanographic parameters in the seasonal and permanent thermocline regions are not the smooth curves observed by older techniques. Rather they indicate a large number of nearly homogeneous layers, with typical thicknesses of meters or less, separated by interfacial regions where strong gradients exist. Examples of typical layered microstructure profiles from different ocean areas are presented. The effects of such microstructure on sound propagation are examined qualitatively using ray tracing techniques. It was found that the layered microstructure had a significant effect only when rays vertex within the layers, in which case the isointensity loss contours degenerate into a broad scatter of points.
Surface dipole strength by cross-correlation method
Authors: Siddon Thomas E.
Published: October 2005

A new correlation technique enables the determination of local acoustic source strength on the surface of flat plates and simple aerofoil shapes. The method is based on Curle's equation for surface-generated noise and involves cross-correlation between local surface pressure and the farfield acoustic pressure. Flat plate airfoils of circular planform were positioned in a “quiet” open jet airflow. The distribution of dipole strength was obtained by moving the point of surface-pressure measurement around on the surface. Distinctively different distributions were obtained for cases of incident turbulence (airfoil in turbulent mixing layer), separated flow (airfoil at 16° angle of attack in core of jet), and vortex shedding (airfoil at 0° angle of attack in core of the jet). The popular notion that noise comes predominantly from the edges of the plate was not strongly supported. In all cases, however, definite localized source regions were identified. The technique also enabled estimates of the correlation area for the surface-pressure pattern and of the spectrum radiated from each unit of surface area to be made. The correlation areas were generally a small fraction of the plate area (1%–10%).
Comments on “Free vibrations of generally orthotropic plates” [D. Mohan and H. B. Kingsbury, J. Acoust. Soc. Amer. 50, 266–269 (1971)]
Authors: Laura Patricio A.
Published: October 2005

Mohan and Kingsbury [J. Acoust. Soc. Amer. 50, 266–269 (1971)] use the Galerkin method to solve the governing partial differential equation. Beam mode shapes are assumed as coordinate functions. Since the Galerkin method requires that geometric and natural boundary conditions be satisfied simultaneously and since the assumed mode shapes do not comply with both requirements in general, the writer wonders on the effect of this matter on the calculated numerical results.
Comparable tests on linear- and carbon-type microphones
Authors: Bryant H. W.
Published: October 2005

A carbon microphone is shown to have 5 dB less low-frequency sinusoidal output than a magnetic microphone, both judged to have approximately the same voice output level and tonal quality. Evidence is offered to show that the sinusoidal characterization of a carbon microphone does not properly describe its response to a complex, wide-band signal having a high peak factor, such as speech. This results from a greater-than-unity slope for the input-output curve of the carbon instrument. An improved characterization for estimating the subjective performance with speech input was obtained with an excitation signal consisting of a sinusoid plus white noise, the latter being filtered from the output. With this technique, the response curves for the two microphones became comparable and reasonably similar. This information is particularly important for testing carbon microphones designed to have a steep input-output characteristic to exclude farfield sounds.
Fractional-harmonic frequency pairs in nonlinear systems
Authors: Eller Anthony I.
Published: October 2005

Under proper conditions, the response of two coupled nonlinear oscillators, driven by a sinusoidal input, contains a pair of fractional-harmonic frequency components. The frequencies f1 and f2 of the fractional-harmonic pair correspond approximately to the resonance frequencies of the system, and the sum f1 + f2 equals the driving frequency. Conditions for the occurrence of fractional harmonics are examined by an analysis that relates them to a pair of coupled Mathieu equations. Fractional-harmonic components were observed in several nonlinear electrical, mechanical, and acoustical systems. The observations are consistent with qualitative predictions of the analysis.
An environmental-acoustics model for sound propagation in a geostrophic flow
Authors: Franchi E. R. , Jacobson M. J.
Published: October 2005

A model for an ocean region experiencing geostrophic motion is considered. Under suitable simplifying assumptions and boundary conditions, equations of motion are solved for the density and pressure. Next, temperature is found by means of a state equation. Then, the pressure and temperature are used to determine the sound-speed structure induced by the presence of the current. The sound speed is found to depend upon both the magnitude of the current and one's position in the current. For a bottom-mounted source and receiver in the current direction, the model is used to investigate ray geometry, travel time, spreading loss, and the total acoustic field at the receiver. It is shown that the phase and amplitude of the received signal are significantly affected by variations in the current. Further, the dependence of sound speed on current is shown to be important so that these two quantities should not be considered separately as has been done in the past.
Flow noise response of a transducer with radially varying sensitivity
Authors: Randall Robert E.
Published: October 2005

The effect of nonuniform response characteristics on the resolution capability of a transducer is determined by the ratio of the measured to actual power spectrum of pressure or “transducer correction factor,” as it is called in this paper. By using a general polynominal to describe the response characteristics of a small flat circular transducer, a generalized transducer correction factor expression is derived in terms of the coefficients of the polynominal and some tabulated frequency-dependent constants. Also, a matching technique is developed by which the transducer correction factor at a specific frequency is matched with the coefficients of the polynominal defining the response characteristics of the transducer. Thus, in this investigation an expression is derived that provides a relatively simple method for computing the resolution capability of a transducer, and a technique is described for determining the shape of the polynominal representing the response characteristics of a transducer which will then resolve the pressure field in a predetermined manner.
A two-dimensional mathematical model for an acoustically soft parabolic cylinder reflector
Authors: Rogers Peter H.
Published: October 2005

A mathematical model is developed for a perfectly soft (zero impedance) parabolic cylinder reflector driven by a line source coincident with its focal line. The parabolic cylinder is assumed to be infinite in length but of finite aperture. The model enables one to quickly ascertain the major features of the acoustic field when given only the acoustic size of the aperture and focal length. The model is based upon the following two assumptions: (1) there exists a definite shadow zone behind the reflector, and (2) the field “within” the reflector depends primarily on the boundary conditions on the inside surface of the reflector. By means of these assumptions the problem is reduced to solving a boundary-value problem where the radiating surface is an infinite circular cylinder. The reduced problem is then solved with the aid of the fast Fourier transform algorithm. Numerical results obtained with this model are shown to be in agreement with measurements made on two test reflectors.
Experimental digital system for the prediction of underwater sound propagation
Authors: Tate Duane C.
Published: October 2005

An experimental digital system to measure a depth-temperature profile of an area of water and utilize this data for the calculation of sound transmission paths and isointensity loss contours has been designed using commercially available hardware, including temperature measuring equipment, digital computer, and output display unit. Computer software programs were developed to handle the temperature sampling of the ocean water, all calculations to determine the desired results, and output of the resultant data. Numerous field tests were conducted and the experimental data compared with the predicted data to verify the accuracy of the system.
Simultaneous two-channel signal detection. III. 630- and 1400-Hz signals
Authors: Sorkin R. D. , Pohlmann L. D. , Gilliom J. D.
Published: October 2005

Performance in a simultaneous two-frequency detection task was studied under monaural and dichotic conditions of signal presentation. In the basic task a 630-Hz tone, a 1400-Hz tone, neither tone, or both tones occurred with equal likelihood on an experimental trial. The observer had to specify which of these events had occured. Performance was examined: (a) when the signal could occur only in the right earphone channel, and (b) when the 630- and 1400-Hz signals were confined, respectively, to the left and right earphone channels. Single-frequency comparison conditions were also run. A performance decrement was observed in both of the two-frequency conditions compared to the single-frequency condition. However, there was no consistent difference between the monaural and dichotic two-frequency conditions. An analysis of the conditional detection probabilities revealed the presence of a cross-frequency interference effect on trials when a signal was present at the other frequency. This effect was sufficient to account for the differences between single-frequency and two-frequency detection performance.
Holographic testing of loudspeakers
Authors: Shajenko Peter
Published: October 2005

The high dynamic range and extremely high fringe contrast attainable by using double-pulsed holographic interferometry enable one to analyze the performance of a loudspeaker by observing the fine details of the resulting vibration patterns.
Articulatory model for the study of speech production
Authors: Mermelstein P.
Published: October 2005

Study of midsagittal x-ray tracings reveals that the vocal-tract outline can be accurately represented by means of variables specifying the positions of the jaw, tongue body, tongue tip, lips, velum, and hyoid. As the articulators move, they modify the vocal-tract cross-sectional area and the vocal-tract transfer function computed thereform. The speech signal may be synthesized by concatenating the responses to repeated excitation of the quasistatic vocal tract. Vowels are specified in terms of variables denoting the positions of the jaw, tongue body, lips, and velum. Consonants are implemented as transformations on the underlying vowel-derived articulatory states that satisfy given constraints on the position of an articulator relative to the fixed structures. The set of states which satisfy the given constraint corresponds to the allowed productions of the consonant. Coarticulation effects control the selection of the underlying state and thus determine the particular consonant produced. Vowel-consonant-vowel sequences generated with the aid of rules for articulator movement and the articulator-position to vocal-tract cross-sectional-area transformation are intelligible and exhibit coarticulation in agreement with acoustic measurements.
Frequency analysis of Dutch vowels from 50 male speakers
Authors: Pols L. C. W. , Tromp H. R. C. , Plomp R.
Published: October 2005

The frequencies and levels of the first three formants of 12 Dutch vowels were measured. The vowels were spoken by 50 male speakers in an h (vowel) t context. Statistical analysis of these formant variables confirmed that F1 and F2 are the most appropriate two distinctive parameters for describing the spectral differences among the vowel sounds. Maximum likelihood regions were computed and used to classify the vowels, and a score of 71.3% correct classification in the logF1 -logF2 plane was obtained (87.3% if three related pairs are grouped together). These scores rose to 78.3% and 95.2%, respectively, when a simple speaker-dependent correction was applied. The scores are comparable with those obtained in an earlier study in which a principal-components analysis was applied to the 1/3-oct filter levels of the same vowel sounds [Klein, Plomp, and Pols, J. Acoust. Soc. Amer. 48, 999–1009 (1970)]. From the latter data a two-dimensional representation (“optimal plane”) equivalent to the logF1 -logF2 plane could be derived. The relative merits of the two approaches are discussed. For automatic speech recognition in particular, the dimensional analysis is much more attractive than the formant analysis because it is much simpler and can be carried out in real time.
Improvement in the pulse-echo technique for ultrasonic attenuation measurements
Authors: Tripathi R. C. , Gupta A. K. , Verma G. S.
Published: October 2005

In the simple pulse-echo technique succesive multiply reflected pulses, received by the quartz transducer, are amplified by a wide-band amplifier, detected, and finally displayed on the screen of a cathode ray oscilloscope. The observed pulse heights are compared for determination of ultrasonic absorption in the medium. In the present development, the received pulses after amplification, detection, and sufficient reamplification, are connected to a T-adapter. From one of the outputs of this adapter the pulse pattern is observed on one of the beams of a double-beam oscilloscope, while the second output is connected to the input of a single-channel analyzer. Using the analyzer in this way, the pulse heights can be determined directly in volts and then their decibel level can be read on a calibration curve to determine the ultrasonic absorption coefficient in medium. The same has been demonstrated in this paper. Some results of measurements on a few steels, using this technique, have also been reported.
Simple velocity hydrophones for bioacoustic application
Authors: Banner Arnold
Published: October 2005

A design and calibration data are presented for velocity hydrophones which operate vertically or horizontally. The simplicity of construction, broad frequency range, and relatively high sensitivity of these units make them particularly practical for use in bioacoustic research.
Some invariance properties of the wide-band ambiguity function
Authors: Altes R. A.
Published: October 2005

Certain changes in pulse shape do not affect the resolution capability of a sonar system. These changes can be expressed as mathematical transformations that leave invariant important properties of the wide-band ambiguity function. Such transformations provide a large number of signal and filter functions, all of which satisfy a given range-Doppler resolution requirement. The sonar designer can then choose the signal and filter that best satisfy other system constraints (e.g., ease of signal generation and filter synthesis, clutter suppression capability, and peak power).
Impairment to hearing from exposure to noise
Authors: Kryter Karl D.
Published: October 2005

It is found that methods commonly used in medicine for the evaluation of impairment to hearing and the relation of this impairment to noise exposure may lead to significant underestimates of the severity of noise-induced hearing impairment and overestimations of tolerable limits for exposure to noise. Criteria of acceptable degrees of hearing impairment for speech and a criterion of an acceptable percentage of people to suffer noise-induced impairment to hearing are suggested. Procedures are derived for calculating Speech Impairment Risk Percent (SIR) which represents damage effect on hearing of a wide variety of noise environments and which can be used for specifying noise exposure limits that would be rated as tolerable for the suggested, or for other, criteria. The proposed procedures appear to be valid, within the state of present knowledge, for daily continuous or intermittent exposures to steady-state or impulsive noises.
Comments on “Impairment to hearing from exposure to noise” by K. D. Kryter
Authors: Ward W. Dixon
Published: October 2005

The 55-dBA 8-h basic damage-risk criterion proposed by Kryter [J. Acoust. Soc. Am. 53, 1211 (1973)] is held to be unrealistically overconservative because it is based on erroneous assumptions and extrapolations from data.
Noise propagation in corridors
Authors: Davies Huw G.
Published: October 2005

A form of geometrical acoustics approach to high-frequency noise propagation in acoustically treated corridors is presented. Expressions are given for the attenuation of sound for a variety of cases when one or more walls have either high- or low-absorption coefficients, for the transmission of sound through open doorways, and for noise propagation at corridor junctions and corners. Experimental confirmation of the predictions is given.
Underwater sound localization in humans
Authors: Hollien Harry
Published: October 2005

Theory and some empirical evidence would predict that humans should exhibit little ability to localize sounds underwater; however, other observations seemed to contradict this position. In order to provide relavant data on the issue, a pilot study was conducted; its results suggested that man can localize sounds underwater—at least to some degree. Accordingly, a major experiment was carried out utilizing 17 divers, who were free to move their heads but not their bodies, in an underwater localization task. In order to allow precision in the experiment, a Diver Auditory Localization System (DALS) was developed; its design is based on previous structures employed in underwater communication research and consists of an open polyvinyl choloride (VPC) framework to which five 3-m arms and other equipment are attached. The five arms allowed placement—at ear level—of underwater projectors at angles (to the diver) of 0°, 45°, 90°, 270°, and 315°. Subjects responded to four different signals—250-, 1000-, and 6000-Hz sinusoids and thermal noise—at 110 dB SPL (re 0.0002 dyn/cm2); this level is approximately 40 dB re underwater hearing thresholds. Responses to stimuli were accomplished by means of a specially constructed five-position underwater switch coupled to an IBM key punch at the surface. The obtained scores were substantially above chance and demonstrate that humans are capable of at least some sound localization underwater.
Perceiving the range of a sound source when the direction is known
Authors: Molino John
Published: October 2005

A modification is proposed in Hirsch's equation for determining the range of a sound source of unknown strength [H. R. Hirsch, J. Acoust. Soc. Am. 43, 373–374 (1968)]. The modified formula applies to the case where the direction of the sound source is known. Greene's comments on Hirsch's letter are investigated for their ability to predict the limitations on the resolution obtainable in human auditory ranging [D. C. Greene, J. Acoust. Soc. Am. 44, 634 (1968)]. In a brief experiment, two subjects were unable to make distance judgments for sustained pure-tone sources over ranges of 3 to 48 ft.
Impulse-response function corresponding to reflection from a region of continuous impedance change
Authors: Wright Hugh
Published: October 2005

Acoustic reflection from a region of continuously varying specific acoustic impedance is characterized, in the linear circuit sense, by a unit reflection impulse-response function R (t). It is shown that in the absence of attenuation and for modest impedance excursions, the impulse-response function corresponding to reflection from a region which has continuously variable impedance along the incident axis is given by R (2t)≈(dz/dt)/4z, where z(t) is the impedance profile and t is acoustic travel time.
Sound detection and processing by teleost fishes: a critical review
Authors: Popper Arthur N. , Fay Richard R.
Published: October 2005

The purpose of this critical review is to reevaluate the current experimental literature on fish audition based upon evaluation of structural, physiological and behavioral studies. The specific emphasis of the paper will be to (1) review the recent literature on the psychophysiology of hearing in fishes; (2) look at the subject of fish hearing from the standpoint of auditory mechanisms and their relationship to what is known about hearing in terrestrial vertebrates; and (3) emphasize some questions and areas of research which we feel require more investigation. Based on the data reviewed in the paper we have tentatively concluded that the teleost auditory system is well adapted as a temporal analyzer.
Acoustic ray tracing in moving inhomogeneous fluids
Authors: White Richard W.
Published: October 2005

Null geodesics of the metric tensor formed from the coefficients of the second-order terms in the partial differential equation for sound are interpreted as the space-time path histories of sound pulses in a geometric ray trace theory for sound propagation in moving inhomogeneous inviscid fluids.
Average velocity of ultrasound in the human female breast
Authors: Kossoff George , Fry Elizabeth Kelly , Jellins Jack
Published: October 2005

A technique for measuring the in vivo average velocity of ultrasound in the human female breast was developed and applied to determine the range of such values in the breast of normal subjects in the approximate age ranges 20 to 80 years and in subjects with selected breast pathologies. Reasonable correlation of the velocity values with breast tissue type, as determined by x ray (mammography), was obtained, indicating that ultrasonic velocity data provide useful information on the main tissue constituents in the breast and that this technique should allow safe, long-term study of changes that may occur in the composition of such tissues.
Echolocation in bats: A zoologist's view
Authors: Novick Alvin
Published: October 2005

A survey is presented of the variety of echolocation behavior in bats.
Spectral broadening of an acoustic pulse propagating through turbulence
Authors: Brown E. H. , Clifford S. F.
Published: October 2005

The following analysis develops the equation for the scattered acoustic power and spectral broadening of a plane acoustic pulse propagating through atmospheric turbulence that is moving with a uniform wind transverse to the beam. Assuming weak single scattering, the resulting propagation broadening is proportional to the wind velocity divided by the outer scale of turbulence and is independent of the strength of turbulence and total propagation range. Further, the broadening for a medium with variable outer scale and wind shear (e.g., a vertical propagation path) is determined primarily by the highest ratio of transverse wind to outer scale encountered by the pulse.
The potential-method formulation of acoustic-wave scattering by rough surfaces
Authors: Welton P. J.
Published: October 2005

The potential method is extended to treat the reflection and scattering of acoustic waves by rough surfaces. The resulting expression for the scattered pressure contains terms which can be identified as the singly and multiply scattered field components. In addition, a boundary condition that approximately accounts for shadowing is used. Only the singly scattered field term is specialized to a form that is convenient for reflected or scattered pressure and intensity calculations. Finally, the assumption of a randomly rough surface is introduced and very general results concerning the coherent and total scattered fields are obtained.
Temporal acuity as a function of frequency
Authors: Green David M.
Published: October 2005

The ear can discriminate between two transient signals that have identical energy spectra but different phase spectra (hence different waveshapes) as long as the total duration of the signals exceeds about 2 msec. A natural question, but one impossible to answer on the basis of previous work, which used transient signals having a broad energy spectrum, is whether this value for temporal acuity is dependent on the frequency content of the signal. Two types of experiments were conducted to answer this question. In one experiment, the energy spectrum was broad but the temporal cues were restricted to specific regions of the frequency spectra. In the second experiment, two segments of a sinusoid (one 10 dB more intense than the other) was played in one order on the reverse. Both experiments confirm the finding that the value of temporal acuity is about 2 msec and that this value is largely independent of frequency. Also of interest is the fact that for the sinusoidal signals the percentage of correct discriminations of temporal order is a nonmonotonic function of the total duration of the two segments.
The pattern-transformation model of pitch
Authors: Wightman Frederic L.
Published: October 2005

A new approach to pitch perception is outlined in this paper. It is based on what might be called auditory pattern recognition. The general approach is formalized in a mathematical model, the so-called “pattern-transformation model.” In this model an acoustic stimulus is first transformed by the sense organ into a pattern of peripheral neural activity. This peripheral pattern is assumed roughly to represent the power-spectrum of the stimulus. Thus, the temporal fine structure of the stimulus is virtually ignored; the model is phase insensitive. The peripheral pattern is then assumed to be Fourier transformed into another pattern of activity. This second pattern roughly represents the autocorrelation function of the stimulus. Pitch is derived from the positions of maximal activity in this pattern. From preliminary tests it appears that the model can successfully predict the pitch of many types of complex stimuli. In addition, the model provides estimates of pitch “strength” or “clarity.” These estimates also agree, at least qualitatively, with available data.
The acquisition of a new phonological contrast: The case of stop consonants in French-English bilinguals
Authors: Caramazza A. , Yeni-Komshian G. H. , Zurif E. B. , Carbone E.
Published: October 2005

Cross-language studies have shown that Voice Onset Time (VOT) is a sufficient cue to separate initial stop consonants into phonemic categories. The present study used VOT as a linguistic cue in examining the perception and production of stop consonants in three groups of subjects: unilingual Canadian French, unilingual Canadian English, and bilingual French-English speakers. Perception was studied by having subjects label synthetically produced stop-vowel syllables while production was assessed through spectrographic measurements of VOT in word-initial stops. Six stop consonants, common to both languages, were used for these tasks. On the perception task, the two groups of unilingual subjects showed different perceptual crossovers with those of the bilinguals occupying an intermediate position. The production data indicate that VOT measures can separate voicing contrasts for speakers of Canadian English, but not for speakers of Canadian French. The data also show that language switching in bilinguals is well controlled for production but poorly controlled for perception at the phonological level.
Attenuation and dispersion of acoustic energy by atmospheric dust
Authors: Henley David C. , Hoidale Glenn B.
Published: October 2005

Insight into the role of atmospheric dust in the attenuation and dispersion of acoustic energy in the lower troposphere is gained by a comparison of theoretical attenuation coefficients and dispersion functions in the 100- to 107-Hz range for the mechanisms of classical-rotational absorption, molecular absorption, turbulent scattering, and dust absorption for a variety of dust and meterorological conditions. Over most of this frequency range the attenuation due to dust absorption is masked by one or more of the other attenuating mechanisms, but at lower frequencies there appear to be physically realizable dust and meteorological conditions wherein dust absorption may become significant. However, the most significant effect of atmospheric dust upon acoustic energy propagation lies in its dispersion, which is opposite in sign and much larger at lower frequencies than dispersion due to classical and molecular effects. The magnitudes of absorption coefficients and dispersion functions for dust are directly proportional to the particle concentration, and their frequency dependence varies with the particle size distribution.
On the derivation of Zone I spectra for a pulsed finite-amplitude source operating in a nonviscous nondispersive fluid medium
Authors: Fenlon Francis Hugh
Published: October 2005

A mathematical procedure for deriving the complex spectral amplitudes generated by nonlinear interaction of the frequency components of a pulsed finite-amplitude source in a nonviscous nondispersive fluid medium, within a distance prior to shock formation, is established. In order to illustrate the procedure, the nonlinear propagation spectra of a dual frequency pulse and a dual sweep linear FM pulse are derived.
Speaker identification by speech spectrograms: some further observations
Authors: Bolt Richard H. , Cooper Franklin S. , David Edward E. , Denes Peter B. , Pickett James M. , Stevens Kenneth N.
Published: October 2005

This letter reviews recent research on speaker identification by means of comparisons of speech spectrograms by human observers. Various factors affecting the reliability of identification are discussed, particularly those that would be present in practical forensic situations. Our interpretations of the new data lead us to reiterate our previous conclusion: that the degree of reliability of identification under practical conditions has not been scientifically established.