bluuebunny/crossref_metadata_2025 huggingface dataset:
Impedance-tube calibration of a reverberant room for the measurement of sound power in tones
Authors: Bies David Alan , Hansen Colin H.
Published: October 2005

The use of an impedance tube and horn for the absolute calibration of a 180-m3 reverberant room for the measurement of sound power in tones is discussed and demonstrated. The results of the calibration procedure are found to compare quite favorably with results obtained using a one-third-octave-band decay method. For a modal overlap index greater than 5, corresponding to frequencies greater than 400 Hz, the difference in the predictions of the two methods is less than 0.8 dB while at a modal overlap index as low as 1.9, corresponding to a frequency of 264 Hz, the difference is less than 1.6 dB. The results of these tests suggest that the one-third-octave-band decay method is quite sufficient for the qualification of a reverberant room with a modal overlap index of 5 or greater for tone-power measurements. The results of these tests also suggest that any room can be qualified for the measurement of sound power in a tone if it is possible to substitute the mouth of an impedance tube and horn for the source whose sound power is to be measured. The required apparatus is simple and the measurements are easily performed.

Subject Classification: [43]55.65; [43]85.20, [43]85.24.
Numerical prediction of echograms and of the intelligibility of speech in rooms
Authors: Santon François
Published: October 2005

An improved method for the estimation of speech intelligibility in rooms prior to construction is described which takes into account the directional distribution of the echoes and is based on the concept of received energy being partitioned into useful and disturbing energies. Laboratory experiments are described which substantiate the applicability of the method. The possibility of computing the energy accumulated versus time by specified receivers in a room is discussed broadly; it is shown by numerical example that the image method and the ray method give closely similar results. Numerical computations based on the ray method are compared with experimentally derived energy accumulation curves for two different rooms and are found to agree substantially. Since the computational method also predicts the directional distribution as well as the time accumulation of received sound, it is conjectured that accurate predictions of speech intelligibility taking directionality of echoes into account may be made from architectural plans and from a knowledge of surface absorption coefficients.

Subject Classification: [43]55.20, [43]55.40; [43]70.35.
Creating an acoustic synthetic aperture in the ocean
Authors: Williams Ross E.
Published: October 2005

A synthetic aperture experiment was conducted using a ship-towed source and midwater receiving hydrophones buoyed upward 4700 and 8000 ft from bottom moorings in a depth of 17 200 ft. The tows were conducted along straight lines perpendicular to the direction to the hydrophones at ranges of 58, 93, 128, 198, and 268 NM. A cw signal at 400 Hz and a swept FM signal between 350 and 450 Hz were transmitted continuously during the tows. Although major difficulties were encountered in maintaining straight tows in the presence of surface swells, it was possible to construct a number of synthetic apertures for the 400-Hz transmissions on an intermittent basis. The lengths of these apertures extended to 1/2 NM and more, corresponding to coherence time intervals of up to 7 1/2 min in the ocean.

Subject Classification: [43]30.20; [43]60.30.
Vibrational and rotational relaxation of water vapor by water vapor, nitrogen, and argon at 500 °K
Authors: Keeton Roy G. , Bass H. E.
Published: October 2005

Ultrasonic absorption has been measured in mixtures of H2O with 15%, 35%, and 55% Ar and N2 at 500 °K. The classical absorption was subtracted from the measured values and the remainder was analyzed in terms of parallel vibrational and rotational relaxation. By extrapolating to 100% H2O, the rate of self deactivation was found to be (2.0 ± 0.4) × 108 sec−1 atm−1 for vibration and (8.3 ± 0.5) × 108 sec−1 atm−1 for rotation. Extrapolation to 0% H2O yields a rate of (4.0 ± 2.0) × 106 sec−1 atm−1 for H2O vibrational deexcitation by N2 or Ar. The isothermal–isometric rotational relaxation time for H2O in one atm of Ar was found to be (1.2 ± 0.2) × 10−9 sec. These results at 500 °K are compared with other work at higher and lower temperatures in order to form a basis for extrapolating to room temperature.

Subject Classification: [43]35.20, [43]35.35.
Interaural phase discrimination for combination tone stimuli
Authors: Zurek Patrick M. , Leshowitz Barry H.
Published: October 2005

A binaural interaction between the combination tone 2f1—f2 generated by two primary tones and a pure tone of the same frequency was demonstrated in an investigation of interaural phase discrimination. Sensitivity to changes in interaural phase was comparable to that obtained with pure tone stimuli. In a second experiment, combination tones of the same frequency, but different order, generated by independent pairs of primary tones presented to the two ears, were also shown to be easily lateralized. Finally, observers were able to discriminate changes in the phase of a low-frequency combination tone generated by high-frequency primaries, which themselves could not produce a binaural interaction based on phase. The results are in accord with the prevailing conception of combination tones as being functionally identical to spectral components in the stimulus.

Subject Classification: [43]65.56, [43]65.62, [43]65.60.
TTS from neighborhood aircraft noise
Authors: Ward W. Dixon , Cushing E. Marion , Burns Edward M.
Published: October 2005

In an attempt to determine the effect on the auditory threshold of the worst ’’neighborhood’’ exposure to aircraft noise that can reasonably be expected, tape-recorded overpasses, both landings and takeoffs, were reproduced at 111 dBA peak level in a reverberant room. Six-hour exposures to landings or takeoffs at the rate of 1 per 1.5 or 3 min were given to one of two groups of five normal listerners. The mean TTS2 (temporary threshold shift 2 min after exposure) did not reach 5 dB at any frequency in any condition. The possibility of hearing damage from such exposures is therefore judged to be remote, despite the fact that the 8-h ’’equivalent levels’’ of these exposures are as high as 95 dBA. The importance of interruptions in reducing risk is emphasized.

Subject Classification: [43]65.66; [43]50.55, [43]50.70.
On the recovery of physical dimensions of stimuli, using multidimensional scaling
Authors: Morgan Byron J. T. , Woodhead Muriel M. , Webster John C.
Published: October 2005

The results of three confusion experiments (acoustic presentation, visual presentation, and combined acoustic and visual presentation of the stimuli), involving artificial sounds constructed from four physical parameters, are analyzed using nonmetric multidimensional scaling (MDS). It appears that just three of the physical parameters are important in the confusions of these sounds in all three cases. The parameter sets used in the combined and visual presentation experiments were identical and differed from that used in the acoustic presentation experiment.

Subject Classification: [43]65.75, [43]65.58.
Ultrasonic production of reversible changes in the electrical parameters of isolated frog skin
Authors: Coble A. J. , Dunn F.
Published: October 2005

Isolated frog skin was irradiated with 1-MHz noncavitating focused ultrasound, intensity range 1–100 w/cm2, in an adaptation of the Üssing chamber providing continuous perfusion of the specimen. The electrical parameters of the skin, viz., the membrane potential (MP) and the short circuit current (SCC), were monitored continuously before, during, and after the acoustic exposure. The magnitudes of the ultrasonically induced changes, in both parameters, were proportional to the acoustic intensity, though the MP decreased while the SCC increased. Unlinking of the two electrical parameters occurs in that their time courses in response to the ultrasound differ, i.e., the SCC increases continuously for exposures of 0.5 sec and longer while the MP reaches its maximum within 0.5 sec and is not altered with increased duration of exposure.

Subject Classification: [43]80.40; [43]35.75.
Acoustic systems containing curved duct sections
Authors: Rostafinski W.
Published: October 2005

The analysis of waves in bends in acoustical ducting of rectangular cross section is extended to the study of motion near discontinuities. This includes determination of the characteristics of the tangential and radial components of the nonpropagating modes. It is established that attenuation of the nonpropagating modes strongly depends on frequency and that, in general, the sharper the bend, the less attenuation may be expected. Evaluation of a bend’s impedance and of impedance generated reflections is also presented in detail.

Subject Classification: [43]20.45, [43]20.40.
Acoustic power of a moving point source in a moving medium
Authors: Cole J. E. , Sarris I. I.
Published: October 2005

Two expressions for the acoustic power output of a moving point source in a moving acoustic medium are obtained. Each is based on a different definition cited in the literature for the average energy-flux vector in an acoustic medium that is in uniform motion. One of the power expressions is shown to provide results which are unreasonable.

Subject Classification: [43]20.55, [43]20.60; [43]28.60.
Comments on ’’Diffuse sound reflection by maximum length sequences’’ [J. Acoust. Soc. Am. 57, 149–150 (1975)]
Authors: Moharir P. S.
Published: October 2005

Some improvements are suggested to Schroeder’s scheme [J. Acoust. Soc. Am. 57, 149–150 (1975)] of achieving diffuse sound reflection in concert halls.

Subject Classification: [43]55.20, [43]55.40.
Sonoluminescence from water containing dissolved gases
Authors: Young F. Ronald
Published: October 2005

The sonoluminescence from 17 different gases dissolved in water was measured. The results show an inverse relation with the thermal conductivity of the gas. The thermal conduction losses of the gas in the cavitation bubble during its rapid collapse are considered, and an expression found for the final temperature of the gas. The sonoluminescence results for the five rare gases studied agreed with this theory.

Subject Classification: [43]35.68, [43]35.32.
Vibratory response of laminated cylindrical shells embedded in an acoustic fluid
Authors: Harari A. , Sandman B. E.
Published: October 2005

The equations of motion for a three-layered cylindrical shell are derived. The thickness and material properties may be different for each layer. Dissipative materials may also be considered. The solution for a simply supported cylindrical shell excited by a time-harmonic load is obtained in vacuum and in a fluid-acoustic medium. The response of the shell and the corresponding acoustic pressure field is found and illustrated for a specific configuration.

Subject Classification: [43]40.26; [43]20.60.
Mechanical parameters of hearing by bone conduction
Authors: Khanna Shyam M. , Tonndorf Juergen , Queller Judith E.
Published: October 2005

A new, powerful, magnetostrictive bone conduction (BC) vibrator is described. At low output levels, it has a wide frequency range (5 Hz to above 20 kHz), and for midfrequencies undistorted outputs reach up to 50 g in terms of acceleration. BC thresholds and SL’s (the latter determined by AC/BC cancellations) were measured with this vibrator. Both varied with contact force, but much more markedly with contract area, in unoccluded as well as in occluded ears. Sound attenuation boxes, after von Békésy, were used in the unoccluded state. Results of the AC/BC cancellations permitted determination of the external-ear and the inner-ear BC components. With the ear unoccluded, variations with contact area (and/or force) were mainly related to changes of the inner-ear responses, but with the ear occluded, they were related to those of the BC-generated sound pressures in the ear canal for f<2 kHz. At AC and BC threshold, SPL’s in the ear canal had identical values and did not vary with contact area or force for f<2 kHz. For a comparable small contact area, BC acceleration thresholds were similar to those specified in ANSI S3.13−1972. For larger contact areas, however, they were lower, by as much as 25 dB, at some frequencies. These results indicate that acceleration is not a valid indicator of the BC input to the skull.

Subject Classification: [43]65.22, [43]65.80, [43]65.64.
Comment on ’’Interaural alternation, information load, and speech intelligibility’’ [J. Acoust. Soc. Am. 57, 1219–1220 (1975)]
Authors: Speaks Charles
Published: October 2005

Wingfield and Wheale [J. Acoust. Soc. Am 57, 1219–1220 (1975)] claim that detrimental effects of interaural alternation on speech intelligibility may not occur unless the listener is placed under some ’’load’’ that is imposed by either a shadowing response, greater linguistic complexity in the message, or a higher input rate of speech. These three sources of load do not appear to be of equal importance. Further, because of the complex interactions among the three sources, based on their results and those of previously reported experiments, it is hazardous to conclude that intelligibility is affected adversely by any ’’critical’’ rate of interaural alternation.

Subject Classification: [43]70.30, [43]70.35.
Reply to ’’Comments on ’Sabine’s reverberation time and ergodic auditoriums’ ’’ [J. Acoust. Soc. Am. 60, 506–508 (1976)]
Authors: Joyce W. B.
Published: October 2005

Gomperts and I apparently maintain our differences on a number of points which are summarized.

Subject Classification: [43]55.20, [43]55.30, [43]55.55.
Energy spectrum analysis: A model of echolocation processing
Authors: Johnson Richard A. , Titlebaum Edward L.
Published: October 2005

Previous analyses of echolocation have suggested that correlation-equivalent processing might be used in certain cases. A frequency domain approach based on energy spectrum analysis of the signal and its echoes combined is proposed as the processing mechanism for echolocation. It is a generalized wide-band mechanism and can account for the large diversity of wide-band signals known to be used for orientation. Neurobiological investigations neither confirm nor deny any specific kind of correlation equivalent processing, but this proposal offers the first frequency domain correlation-equivalent possibility. A review of time separation pitch reveals that an identical analysis has been used to explain that phenomenon. Extensions of the model can explain many of the phenomena observed in echoloction.

Subject Classification: [43]80.50, [43]80.60; [43]60.40; [43]65.62, [43]65.68.
Acoustical effects in panel response to supersonic turbulence
Authors: Pope Larry D.
Published: October 2005

Acoustical coupling of a turbulence-excited panel and a supersonically moving fluid is investigated. Response of a panel with a single rib discontinuity is considered. Radiation from the panel into the fluid induced by a uniform line force is investigated and the line admittance of the panel in the presence of supersonic flow is obtained. Numerical results are presented for the line admittance and for the ribbed and unribbed infinite panel response. A relation is given which upon integration will yield the radiation damping of a finite panel (radiation into the supersonic flow).

Subject Classification: [43]40.35; [43]28.65; [43]20.60.
Subharmonic pitches of a pure tone at low S/N ratio
Authors: Houtgast T.
Published: October 2005

2AFC scores were obtained on 50 untrained subjects who had to respond to a 3% increment or decrement of the fundamental frequency of two successive signals. The first signal in each trial was a reference, containing six harmonics of 200 Hz. Main variables were the number of harmonics of the second signal in a trial (either 3, 2, or 1) and the presence or absence of continuous background noise. Low scores were observed in the absence of the noise (typically 65% for the 3- and 2-component signals, and virtually 50% for the 1-component signals), whereas in the presence of the noise much higher scores were observed (typically 90% and 80%, respectively). The results indicate that background noise has great impact on the perceptibility of a ’’low pitch’’ related to the fundamental frequency, even more so than the number of components presented (within the range of three, two, or one components): at a low S/N ratio, even a single harmonic may give rise to the perception of a subharmonic low pitch. Subsequent experiments with three trained subjects indicated that this potential of a single pure tone to evoke a subharmonic pitch deteriorates for harmonic numbers of about n=7 to 11. The theoretical implications of these subharmonic pitches of a pure tone to pitch perception in general are discussed.

Subject Classification: [43]65.54, [43]65.75, [43]65.35.
Gap detection with three auditory events—a single-channel process
Authors: Williams Kendrick N. , Elfner Lloyd F.
Published: October 2005

Temporal resolution of a silent interval (gap) imbedded in a three-tonal-pulse train was investigated. Two frequencies were alternated in a three-event array where the gap could appear between the first and second or second and third auditory event. Frequency and gap position effects were systematically explored using a temporal two-interval forced-choice paradigm and a modified tracking procedure. Gap detection was found to vary as a function of antecedent event duration and signal-comparison stimulus similarity. Indications of a filter process similar in bandwidth to the empirical critical band was found in fully correlated signal-comparison stimulus conditions. Obtained results are consistent with fixed-filter signal-envelope detection models found in the simultaneous and forward-masking literature.

Subject Classification: [43]65.75, [43]65.68.
Digital analysis of laryngeal control in speech production
Authors: Flanagan J. L. , Rabiner L. R. , Christopher D. , Bock D. E. , Shipp T.
Published: October 2005

Physiological measurements are made directly on human talkers to determine several dynamic laryngeal functions. The functions are control variables in a speech synthesizer which utilizes acoustic models of the vocal cords and vocal tract. The functions are measured simultaneously and recorded on multichannel FM tape. They are the time variation of vocal-cord (glottal) opening (Ag); the electromyographic (EMG) potentials of three laryngeal muscles−−posterior crico-arytenoid (PCA), interarytenoid (IA), and crico-thyroid (CT); the subglottal air pressure (Ps); the speech output sound pressure waveform (P); and timing pulses from a digital clock. Preliminary data for ten utterances by a man are digitized by a multiplexed A/D converter on a DDP−516 computer, and the results are stored in disk file for analysis. Bandwidth of the multitrack FM playback is 2800 Hz. Each function is sampled at 6250 sec−1 and quantized to 16 bits. Digital filtering is applied to remove dc offsets and enhance information features. The acoustic functions (Ag, Ps, and P) are submitted to programmed pitch analysis. The results show how voice periodicity can be manifested differently at the glottal and sound-output levels. A typical instance is vocal-cord vibration throughout the occluded phase of a voiced stop consonant. The EMG functions are analyzed by computing short-time energy. The results are correlated with voicing onset/offset and with voice pitch. PCA energy is shown to be correlated with voicing offset, and anticipatory to it by about 20–30 msec. IA energy is shown to be correlated with voicing onset, and anticipatory to it by about 40–50 msec. CT energy is found to be nearly directly correlated with the frequency contour for voice pitch. Direct utilization of these physiological parameters for speech synthesis is suggested.

Subject Classification: [43]70.20, [43]70.60.
Jet-drive mechanism in organ pipes
Authors: Fletcher N. H.
Published: October 2005

The analysis given by Elder [J. Acoust. Soc. Am. 54, 1554 (1973)] of the mechanism of interaction between a time-varying air jet flow velocity and a resonant organ pipe is extended to deal with the case in which a jet of fixed flow velocity is deflected to cut a sharp pipe lip. Similar terms arise in the analysis but the nonlinearities are less important than in Elder’s case. The generation of higher transverse pipe modes by the jet asymmetry is considered and it is concluded that such modes may play a significant part in coupling ordinary pipe modes to pipe-wall vibrations.

Subject Classification: [43]75.60.
Spatial correlation of wind-generated noise at very low frequencies
Authors: Wilson James H.
Published: October 2005

Analysis of the ambient-noise horizontal directionality data from a recent environmental acoustic exercise indicates that wind-generated noise at 10 Hz is spatially correlated over large apertures. The noise levels measured by a large aperture, linear towed array were highest near broadside during high-wind conditions. Spatially correlated wind-generated noise arriving from the sea surface directly above the array is offered as a possible explanation and is consistent with results of previous wind-noise experiments. In the limiting case of very high wind speeds (?35 knots), the array response measured for this nearfield effect closely approximated the farfield broadside beam pattern at 10 Hz. At lower wind speed, the array response was wider near broadside. This implies that the spatial correlation of wind-generated noise at 10 Hz becomes greater as the wind speed increases.

Subject Classification: [43]28.20, [43]28.65; [43]50.80.
Ambient sea noise in waters near Australia
Authors: Cato D. H.
Published: October 2005

Ambient sea noise has been measured at 40 positions in mainly tropical waters near Australia: in the Indian Ocean; the Arafura and Timor Seas; and in the Coral and Tasman Seas (Pacific Ocean). Wind-speed dependence was observed at all frequencies of measurement from 22 to 5000 Hz. At hydrophones suspended at depths between 8 and 25 m, the wind- dependent noise appeared to be independent of bottom depth which varied from 26 to 6700 m. The rate at which wind-dependent noise increased with increasing wind speed was found to be significantly less than has been observed in the North Atlantic Ocean. Non-wind-dependent noise, observed at frequencies below 250 Hz, varied by about 10 dB within a particular sea and by up to 20 dB between seas, and could be broadly related to the relative shipping densities and propagation conditions in the individual seas. In the shallow Arafura and Timor Seas north of Australia, there is evidence that noise of distant shipping is not a significant component of the ambient noise. A model of traffic noise in the Tasman Sea predicts levels in agreement with observed noise levels.

Subject Classification: [43]30.70.
Use of phase measurements for arrival-time extraction of overlapping sinusoidal signals in shallow water
Authors: Fjell Per O.
Published: October 2005

The use of phase measurement for sinusoidal signal arrival-time extraction of overlapping signals subjected to multipath conditions in shallow water is considered. The phase-measurement method is applied to signal data from a research cruise. The method does not give convincing results. For distances greater than 10 000 m the results are negative. The results obtained are strongly dependent on the sound velocity profile. The signal pulse length was a very important parameter in the results. The optimal pulse length was shown to be greater than 10 msec and less than 100 msec regardless of the hydrophone depth for the two depths investigated.

Subject Classification: [43]30.20; [43]60.30.
Nearfield beam patterns of exponentially shaded end-fire line arrays
Authors: Mellen Robert H.
Published: October 2005

A contour integration method of calculating nearfield beam patterns of continuous, exponentially shaded, end-fire line arrays is presented. Only semi-infinite arrays are considered; however, the method can be applied to arrays of finite length.

Subject Classification: [43]30.85, [43]30.75; [43]25.35.
Acoustic reflex, loudness summation, and the critical band
Authors: Scharf Bertram
Published: October 2005

As the bandwidth of a sound increases up to the critical bandwidth, loudness remains constant so long as overall intensity is constant. To keep loudness constant at wider bandwidths, intensity must be reduced. Similarly, the minimum intensity required to activate the acoustic reflex (AR) is constant as bandwidth is increased up to a critical value; beyond that value, intensity can be reduced. This critical width is much wider for the AR than for loudness summation. The literature and some new data show that the difference does not arise simply because the AR is measured at signal levels higher than those at which loudness summation is usually measured. Measured at the same high signal levels as needed to activate the AR, the critical band in loudness summation appears to be about two times wider than at lower levels; the ’’critical bandwidth’’ measured for the AR is some four to six times wider. Moreover, the AR shows a strong dependence on the number of components in a multitone complex, whereas loudness summation does not. Also, at very wide bandwidths the AR threshold shows a much larger decrease than would be predicted by the change in loudness. These differences suggest that the AR is not a direct corollary of loudness.

Subject Classification: [43]65.22, [43]65.50, [43]65.75.
Acoustic estimates of fish density and scattering function
Authors: Peterson Miles L. , Clay Clarence S. , Brandt Stephen B.
Published: October 2005

The amplitude of a sonar echo from a fish depends upon the species and size of the fish, acoustic wavelength, aspect, position of the fish in the sonar beam, range and backscattering cross section. We simplify the problem to a single species and size of fish, vertically downward echo sounding, single aspect, and nonoverlapping echoes. After removal of attenuation due to range and absorption two random functions remain. The position of the fish in the sonar beam is random and the scattering cross section for each trail is random. We assume that the fish have a uniform density (number/m3) and calculate the probability density function (PDF) for insonification and reception. We assume that the PDF of the envelope of the echo (excluding the variability of insonification and reception) has a Rayleigh PDF. Assuming two PDF’s are independent, we calculate the PDF of the echo envelopes wE(e). wE(e) depends upon the beamwidth of the sonar and the mean backscattering cross section. The theoretical PDF has the same shape as the measured PDF of echoes from alewife in Lake Michigan. We use the fit of the PDF’s to estimate the backscattering cross section and fish density. This calibrates the echo-integration processing system. A profile of the density of alewife in Lake Michigan is shown.

Subject Classification: [43]30.40; [43]80.40.
Scattering matrix for elastic waves. I. Theory
Authors: Varatharajulu Vasundara , Pao Yih-Hsing
Published: October 2005

A matrix theory is developed for investigating the scattering of elastic waves in solids by an obstacle of arbitrary shape. The scattering matrix which depends only on the shape and nature of the obstacle relates the scattered field to any type of harmonic incident field. Expressions are obtained for the elements of the scattering matrix in the form of surface integrals around the boundary of the obstacle, which can be evaluated numerically. Using the principle of reciprocity and the conservation of energy, the scattering matrix is shown to be symmetric and unitary. These properties are essential to assure the accuracy of numerical calculations. Both two- and three-dimensional problems are discussed, and the obstacle may be an elastic inclusion, a fluid inclusion, a cavity, or a rigid inclusion of arbitrary shape.

Subject Classification: [43]20.15, [43]20.30.
Matrix theory of elastic wave scattering
Authors: Waterman P. C.
Published: October 2005

Upon invoking Huygen’s principle, matrix equations are obtained describing the scattering of waves by an obstacle of arbitrary shape immersed in an elastic medium. New relations are found connecting surface tractions with the divergence and curl of the displacement, and conservation laws are discussed. When mode conversion effects are arbitrarily suppressed by resetting appropriate matrix elements to zero, the equations reduce to a simultaneous description of acoustic and electromagnetic scattering by the obstacle at hand. Unification with acoustic/electromagnetics should provide useful guidelines in elasticity. Approximate numerical equality is shown to exist between certain of the scattering coefficients for hard and soft spheres. For penetrable spheres, explicit analytical results are found for the first time.

Subject Classification: [43]20.15, [43]20.30.
A near-wake model for the aerodynamic pressures exerted on singing trailing edges
Authors: Blake William K.
Published: October 2005

Periodic vortex streets are formed in the wakes of blunted trailing edges on airfoils and struts. The pressures generated on the shedding struts by the vortices in these wakes are periodic in time with a frequency that is set by the shedding rate for the vortices. A simple analytical formulation is derived to relate wake-induced pressures to the characteristics of the wake near the edge. The chordwise distribution and magnitude of the pressure is shown as a function of the circulation of shed vortices, as well as the formation distance and the spacing of the vortices in the street. Predictions from the theory are compared to some recent measurements which were obtained in the wakes downstream of different trailing edges. These measurements were made at Reynolds numbers, based on trailing edge thickness, on the order of 104 to 105.

Subject Classification: [43]28.65; [43]50.55.
Vortex-shedding noise from oscillating cylinders
Authors: Burton T. E. , Blevins R. D.
Published: October 2005

The theory of sound radiation from cylinders vibrating in resonance with vortex shedding is extended to consider the effects of vibration amplitude and mode shape. Farfield intensity and total radiated power are expressed as functions of given structural and flow parameters. Closed form solutions for intensity are obtained when cylinder vibration velocity is either much smaller than or comparable to mean flow velocity.

Subject Classification: [43]28.65, [43]40.26, [43]50.55.
The ac and dc components in lateral line microphonic potentials
Authors: Boston J. R.
Published: October 2005

Measurements of the microphonic potential from the lateral line sensory organs of killifish (Fundulus heteroclitus) are presented in this report. The potential consists of a dc shift and a dominant oscillatory component at twice the frequency of the stimulus, and it grows with the square of the stimulus at low amplitudes. An electrical circuit model of the microphonic is developed, assuming a simple quadratic nonlinearity in the electrical response of an individual hair cell as suggested by Flock. The model allows investigation of variable conductive or variable capacitive effects in microphonic generation, and the results obtained from the model are compared to the observed properties of the microphonic potentials. It is concluded that hair cell microphonics appear to be generated by a process involving current flow through a variable conductance, although capacitive effects of the hair cell are important in determining the waveform of the microphonic and its behavior as a function of frequency. A discrepancy between the observed low-amplitude growth of the microphonic in killifish and the reported low-amplitude growth of the microphonic in other acoustico-lateralis preparations is also discussed.

Subject Classification: [43]65.28, [43]65.20, [43]65.40.
Growth of loudness at 1000 and 3000 Hz
Authors: Hellman Rhona P.
Published: October 2005

Loudness growth at 1000 and 3000 Hz was measured directly by magnitude estimation and production, and indirectly by loudness matches between tone and wide-band noise and by interfrequency matching. The outcome of the three series of experiments does not reveal any systematic difference in shape of the loudness curves at 1000 and 3000 Hz. To a first approximation, above about 30 dB SL the loudness functions at 1000 and 3000 Hz are power functions of sound pressure with an exponent close to the accepted ISO standard of 0.60 (0.30 re sound intensity). Below 30 dB SL both loudness curves become progressively steeper than a simple power function and approach the same limiting slope, re sound intensity, of unity. Consistent with Steven’s calculation system [J. Acoust. Soc. Am. 51, 575–601 (1972)], the data also show that loudness equality is achieved when a 3000-Hz tone is about 8 dB below the SPL of a tone at 1000 Hz.

Subject Classification: [43]65.50, [43]65.75.
Some vocal distinctive features used by gelada monkeys
Authors: Richman Bruce
Published: October 2005

Recordings have been made of gelada monkeys freely vocalizing during normal social interchanges in captivity. Spectrographic analyses and perceptual evaluations of the recordings suggest that these primates produce a greater range of vocal distinctive contrasts than have been observed previously. In particular, evidence is presented which suggests that gelada monkeys are capable of producing three distinctive voice qualities, a wide range of vowel qualities, and a set of consonants that differ in manner of articulation (glides, a fricative, plosives, nasals) and in place of articulation (labial, postdental, velar).

Subject Classification: [43]70.40, [43]70.20; [43]80.50.
Measurement of acoustoelastic and third-order elastic constants for rail steel
Authors: Egle D. M. , Bray D. E.
Published: October 2005

Measurements of the stress-induced changes in ultrasonic wave speeds in steels typically used in railroad rails are presented. All of the five possible relative changes in wave speeds for a uniaxial state of stress have been determined and agree, to within the limits of accuracy of the measurement, with the second-order theory of Hughes and Kelly. The third-order elastic constants are calculated from the acoustoelastic data.

Subject Classification: [43]85.20, [43]85.22, [43]35.26.
Low-frequency coherence transverse to the direction of propagation
Authors: Fitzgerald R. M. , Guthrie A. N. , Shaffer J. D.
Published: October 2005

Experimental evidence is presented which indicates that the coherence of 10 Hz signals in the deep ocean is sufficient to form a passive-transverse synthetic aperture in excess of 1600 m.

Subject Classification: [43]30.20.
Prediction of noise distribution in various enclosures from free-field measurements
Authors: Galaitsis Anthony G. , Patterson William N.
Published: October 2005

The image theory method is used to predict sound pressure levels generated by an acoustic source of known strength in regular rooms, tunnels, and flat rooms. For regular rooms, the results are identical to those of the well-established diffuse field theory. For tunnels and flat rooms, the predictions are verified by direct measurements taken in underground mines.

Subject Classification: [43]55.20, [43]55.55.
Acoustic-phase fluctuations induced by internal waves in the ocean
Authors: Desaubies Yves J. F.
Published: October 2005

Acoustic-phase fluctuations induced by internal waves in the ocean are calculated in the geometric approximation. The results compare favorably with available experimental data.

Subject Classification: [43]30; [43]28.60.
Modified phase integral approximation for a more rigorous ray tracing technique
Authors: Floyd Edward R.
Published: October 2005

The phase integral approximation is modified to describe wave propagation in three dimensions without any singularities at classical turning points. For stratified media a rigorous ray tracing scheme is derived. Stratified media are shown in general to induce dispersion. The connections to both the normal mode and filter theory methods are discussed. The effects of oceanic surface thermoclines upon rigorous ray tracing are shown to be frequency dependent.

Subject Classification: [43]30.20; [43]20.15.
Nonspectral pitch
Authors: Burns Edward M. , Viemeister Neal F.
Published: October 2005

The spectrum of amplitude-modulated wide-band noise is invariant with changes in modulation frequency, and consequently such waveforms cannot convey melodic information by spectral changes. The results of several experiments indicate, however, that sinusoidally amplitude-modulated wide-band noise does have pitchlike properties. Simple melodies can be identified when the ’’notes’’ correspond to different modulation frequencies. More importantly, musically trained observers can immediately recognize melodic muscial intervals composed of such waveforms. The pitchlike properties of modulated noise are maintained when the modulated noise is bandpass filtered and when an unmodulated band-reject masker is added to the bandpass noise. Presumably the perception of pitch elicited by modulated noise is based upon temporal information in the envelope of the waveform. This ’’temporal pitch’’ is less salient than the pitch elicited by pure tones. Also, temporal pitch can be elicited only over a restricted range of modulation frequencies. The upper limit (approximately 850–1000 Hz) appears to reflect the inability of the auditory system to follow rapid temporal changes.

Subject Classification: [43]65.54, [43]65.75.
Response to ’’Comments on ’Diffuse sound reflection by maximum length sequences’ ’’ [J. Acoust. Soc. Am. 60,268–268(1976)]
Authors: Schroeder M. R. , Gerlach R.
Published: October 2005

Complementary maximum length sequences, recently proposed by Moharir,1 do not give as good sound diffusors as those originally proposed by Schroeder.2 A rule for constructing two-dimensional sequences is given.

Subject Classification: [43]55.20, [43]55.40.
Multipath scintillation spectra
Authors: Adams Stanley L.
Published: October 2005

In a recent paper by Dyson, Munk, and Zetler [’’Interpretation of multipath scintillations Eleuthera to Bermuda in terms of internal waves and tides,’’ J. Acoust. Soc. Am. 59, 1121–1133 (1976)], approximate expressions were derived for the spectrum of the phase and intensity scintillations of a sinusoidal signal after propagation through a certain random multipath channel. From the multipath structure specified in that paper, exact results are obtained for the phase-derivative fluctuation spectrum. This expression can be easily evaluated and compared to the approximation. In addition, amplitude and square-amplitude fluctuation spectra are derived.

Subject Classification: [43]30.20, [43]30.30.
Use of a nearfield array for acoustic backscattering cross-section measurments
Authors: Fiorito Ralph , Madigosky Walter
Published: October 2005

It is theoretically demonstrated that a circular piston operating at high frequency can be used as a nearfield array to receive and measure farfield backscattering (sonar) cross sections. Experiments are described which use a 4.75-in.-diam piston operating at 15 MHz as a transmitter/receiver within the nearfield zones of the piston and scattering object. Results obtained are in good agreement with those theoretically predicted by finite-beam insonification-scattering theory. Comparison of scaled-model ship measurements with farfield values shows reasonable agreement as well.

Subject Classification: [43]30.82; [43]30.40.
Turbulent-boundary-layer noise in the interior of aircraft operating at varying altitudes
Authors: Bray Don E.
Published: October 2005

The effect of altitude on the interior noise level of commerical aircraft has been studied. Changes in noise levels are shown to be very closely related to the square of the local air density. Data collected on regularly scheduled flights on the C scale and the A scale are generally seen to be in very good agreement with the predicted changes.

Subject Classification: [43]50.50, [43]50.55; [43]28.65.
Influence of subarachnoid structures on transmeningeal ultrasonic propagation
Authors: Johnston R. L. , Dunn F.
Published: October 2005

The previously observed frequency dependence of the ultrasonic threshold dose, for production of irreversible lesions in mammalian brain, is ascribed to the brain meninges. The collagenous trabeculae of the subarachnoid space, interposed between the arachnoid and the pia mater, are considered responsible by virtue of the increased elastic moduli associated with their structural supporting role. A plane three media model provides acoustical parameters of these anatomic structures. The method provides the frequency-independent lesion-threshold function It1/2=200 W/cm2 sec−1/2.

Subject Classification: [43]80.40.[43]80.20
Rayleigh disk in an aligned nematic liquid crystal
Authors: Hayes C. F.
Published: October 2005

If a Rayleigh disk were suspended in an aligned nematic liquid crystal there would be two torques acting on the disk: one due to the acoustic wave and the other an elastic torque due to the liquid crystal. For a disk of radius 50 μm an acoustic intensity typically of ∠1 mW/cm2 would orient the disk at 45° to the direction of the incident wave if the acoustic wave is directed perpendicular to the optic axis of the liquid crystal. The applicability to detection of acoustic fields is noted.

Subject Classification: [43]85.35.
Spherical-wave reflection from a boundary of reactive impedance using a modification of Cagniard’s method
Authors: Donato R. J.
Published: October 2005

The solution using Cagniard’s method for the reflection of a spherical wave from a locally reacting plane boundary is compared to that using the steepest descents method. The contribution from the presence of a pole is less arbitrary using this method and the transition from the pole to the no pole case is shown to be gradual. A further solution in the time domain for an incident time impluse function is also derived.

Subject Classification: [43]20.15, [43]20.30; [43]28.40.
Brainstem auditory evoked responses in man. I. Effect of stimulus rise–fall time and duration
Authors: Hecox Kurt , Squires Nancy , Galambos Robert
Published: October 2005

Short latency (under 10 msec) evoked responses elicited by bursts of white noise were recorded from the scalp of human subjects. Response alterations produced by changes in the noise-burst duration (on time), interburst interval (off time), and onset and offset shapes are reported and evaluated. The latency of the most prominent response component, wave V, was markedly delayed with increases in stimulus rise time but was unaffected by changes in fall time. Increase in stimulus duration and therefore loudness resulted in a systematic increse in latency, probably due to response recovery processes, as this effect was eliminated with increases in stimulus off time. The amplitude of wave V was insensitive to changes in signal rise and fall times, while increasing signal on time produced smaller amplitude responses only for sufficiently short off times. It is concluded that wave V of the human auditory brainstem-evoked response is solely an onset response.

Subject Classification :[43]65.59.[43].65.75.
Graphical method for reflection of plane waves in a micropolar half space
Authors: Ozgur Dincer , Cakmak Ahmet S.
Published: October 2005

Analysis of reflection of plane waves from a flat boundary in a micropolar half space poses tedious calculations. In this paper, utilizing the concept of slowness surfaces, a simple and efficient method is proposed as an alternative to the previous analytical methods. Critical angles of incidence, the nature of the reflected body, and boundary waves corresponding to the incident longitudinal displacement and coupled transverse displacement microtational waves are studied.

Subject Classification: [43]20.15, [43]20.30.
Angle-depth diagram for use in underwater acoustics
Authors: Flatté Stanley M.
Published: October 2005

The value of a diagram in which the angle of an acoustic ray is plotted versus its depth is explored. The concept of source line in angle-depth space is developed. Characteristics of different sound channels, reflection, multipath, caustics, and the analysis of obstacles such as seamounts are described within the context of the diagram. The application of Liouville’s theorem is discussed.

Subject Classification: [43]30.20; [43]20.20.
Image profiles in schlieren observations of acoustic wave fronts
Authors: Bucaro J. A. , Flax L. , Dardy H. D. , Moore W. E.
Published: October 2005

Image-intensity functions have been calculated for acousto-optic phase-resolved schlieren in the phase grating (Raman–Nath) diffraction limit. The calculation applies to the case where a circular stop is used. Any number of diffraction orders may be stopped. The results are programmed into a laboratory GT-44/PDP-11 real-time graphic system and compared to experimental observations. The latter include TV monitoring of both the diffraction orders and the image distribution and photomultiplier-pinhole recording of the image-intensity distribution. It appears that phase resolution will permit quantitative pressure level determinations. The results aid significantly in interpreting phase-resolved schlieren observations from radiation and scattering mechanisms.

Subject Classification: [43]35.65.
Method to convolve sound-level distributions for prediction of community sound levels
Authors: Kessler Frederick M. , Gottlieb Peter
Published: October 2005

Predicting community noise levels requires the addition of background ambient sound levels and the source’s contribution to ambient sound levels. Baseline data are obtained, from community sound surveys, in the form of histograms and cumulative distributions. Source (for example, a construction site) sound level data are also obtained as histograms and cumulative distributions. The problem of combining the two distributions is made somewhat difficult by the logarithmic nature of the physical variable. The prediction is accomplished by the mathematical convolution of the variables representing baseline and the source. Since the data are provided as histograms rather than as continuous probability density functions, it is convenient to decompose the density functions into a sequence of Dirac delta functions. The result can be programmed for a rapid and efficient computation. Results are provided for the combination of various construction site sound level distributions (e.g., normal and bimodal) with community background ambient sound. Data are shown of the effect on community noise of a source contribution which is attenuated by distance.

Subject Classification: [43]50.75.
Auditory-nerve-fiber bandwidths and critical bandwidths in the cat
Authors: Pickles J. O. , Comis S. D.
Published: October 2005

The effective bandwidths of cat auditory-nerve fibers were estimated electrophysiologically from the masked thresholds of tones at the nerve fibers’ characteristic frequency. The masking noise was of variable bandwidth but constant total power and was geometrically centered on the characteristic frequency. It was presented at an intensity which, for the narrowest masker bandwidth used, raised the tone threshold by about 20 dB. The point at which the masked tone threshold began to decline as the masker bandwidth was increased provided an estimate of the fiber’s effective bandwidth. A similar method had been used in earlier psychophysical estimates of the cat’s critical band. The auditory-nerve-fiber bandwidths were on average 6 dB less than the critical bandwidth at the same frequency. Two of the cats had been tested both psychophysically and electrophysiologically; in these cats the difference was 6.8 dB. Most fibers, moreover, had critical ratios less than that observed psychophysically. The results suggest that the critical band is not a simple correlate of the tuning curves of auditory-nerve fibers.

Subject Classification: [43]65.42, [43]65.58.