bluuebunny/crossref_metadata_2025 huggingface dataset:
Transmitting SAW hydrophone
Authors: Das P. , Lanzl C. , Barone D.
Published: October 2005

A transmitting hydrophone which remotely senses both absolute pressure and changes in pressure has been developed using a surface-acoustic-wave (SAW) oscillator. This oscillator is formed by placing a SAW delay line or resonator in the feedback loop of an amplifier. The pressure applied to the hydrophone is converted to a flexural loading of the piezoelectric plate which alters the surface-wave velocity on the plate, consequently shifting the oscillator frequency. This frequency modulated signal is easily transmitted to a remote location for signal recovery. The piezoelectric plate thickness and length can be chosen to optimize the sensitivity of the SAW hydrophone. The surface-wave element of the oscillator is a planar structure; therefore, it is simple and inexpensive to manufacture. Furthermore, the size and power requirements of the SAW hydrophone are small, typically less than 50 cm3 a and 300 mW. This paper presents performance data of a number of SAW hydrophones using SAW oscillators in the 40–100-MHz range in conjunction with a versatile signal demodulation system. Extensive measurements of sensitivity and frequency response were made for both delay line and resonator hydrophones manufactured on LiNbO3 and S-T cut quartz substrates and compared with measurements obtained from conventional hydrophones in the identical setup. [Work supported by Naval Electronics Systems Command Contract No. N00039-78-C-0042.]
Lateralization of clicks presented at a rapid rate
Authors: Hafter E. R. , Dye R. H.
Published: October 2005

Interaural differences of time (Δt's) can be detected in signals of high spectral content, if sufficient “recovery” time is allowed between successive stimulations. Listeners were asked to detect Δt's in trains of n (n = 1 to 32) dichotic clicks (4000-Hz, bandpass). Interclick intervals (ICIs) were 1, 2, 5, or 10 ms, jittered by ±10% to avoid unwanted pitch cues. The mechanisms of “recovery” can be studied from the relation between N, the number of neural events, and n. If the auditory system integrates information over the duration of a click train, the slope of a log Δt vs logN plot should be −0.5. Suppose that the need for “recovery” reflects neural refraction. If so, then N should be a proportion of n [N = 1 + k(n − 1); 0 ⩽ k ⩽ 1; k = f(ICI)] and the slopes of the log-log plots constant across ICIs. On the other hand, if the “recovery” period indicates fatigue or the build up of inhibition, then each click in the more rapid trains has a smaller probability of producing a neural event than the one before [N = nk; 0 ⩽ k ⩽ 1; k = f(ICI)]. Our data support this second model, with the slopes of the functions decreasing with ICI.
Acoustics of an East Australian current anticyclonic eddy
Authors: Scully-Power P. D. , Nysen P. A. , Browning D. G.
Published: October 2005

The sound transmission characteristics of a typical eddy associated with the East Australian current during the Southern Hemisphere summer have been measured for the frequencies 25–2000 Hz. The dominant acoustic features of this warm core eddy were a 36-m surface duct and a deeper 175-m thick eddy duct. The eddy duct behaved as a classical acoustic wave guide with an optimum transmission frequency of 100 Hz. Strong acoustic coupling was observed between the ducts with rays up to 20 deg from the source in the surface duct being trapped in eddy duct. The coupling was independent of range and weakest for the frequency range 300–1000 Hz. Below 300 Hz coupling steadily increased due to diffracted energy. Above 1000 Hz coupling also increased due to scattered energy. [Work Partially Sponsored by Office of Naval Research.]
General analysis of ocean eddy effects for sound transmission applications
Authors: Henrick R. F. , Siegmann W. L. , Jacobson M. J.
Published: October 2005

An analytical approach is used to obtain an approximate solution for deep-ocean mesoscale eddies, including depth-dependent effects. The solution is used in the development of an environmental-acoustics model which relates acoustically relevant quantities, such as sound-speed and current distributions, to eddy parameters. Parameters of the model are depth of influence, radius, rotational direction and maximum speed, and translational velocity. An application to a particular Gulf Stream ring is made, and the resulting current and soundspeed structures are shown to be in good agreement with observations. Then, general results are presented for rotational current structure, maximum horizontal sound-speed change, and maximum SOFAR-axis elevation as functions of eddy radius and peak current speed. It is shown explicitly how these quantities change significantly with eddy size and strength. This model provides a basis for subsequent analytical studies of sound transmission through an arbitrary eddy or eddy field. [Work supported by ONR.]
Mode conversion in shallow-water sound propagation
Authors: McDaniel Suzanne T.
Published: October 2005

Coupled equations for modal power transfer are applied to calculate the energy transferred between normal modes as a result of scattering from the ocean floor. Numerical estimates are presented for mode conversion in a typical shallow-water environment. The results show that mode coupling can have a significant effect on propagation loss. Mode-coupling predictions obtained for farfield transmission loss are found to display both frequency- and range-dependent features in qualitative agreement with observed shallow-water transmission loss. Excellent agreement is obtained between mode-coupling predictions and experimentally measured mode attenuation. [Work supported by Naval Sea Systems Command.]
Simulation of sound absorption in seawater
Authors: Atkinson G. A. , Enwall E. , Endo H.
Published: October 2005

In our original simulation model [J. Acoust. Soc. Am. 54, 996 (1973)] we modeled sound absorption in seawater with the coupled system (Mg+2, SO4−2, CO2, H2O) and achieved reasonable fits to the ocean data. The main absorption is due to the Mg+2SO4−2 ion pairing but the low-frequency (< 10 kHz) excess was attributed to the Mg+2-HCO3− ion-pairing process. The quantitative fit was very dependent on the parameters of the Mg+2-SO4−2 process. We have recently redetermined the MgSO4 system with much greater precision. In addition we have examined the sound absorption due to Na+-SO4−2 ion-pairing and the popular boric acid-borate process. We present a more elaborate simulation of seawater absorption using all of the above data. The simulation provides a more meaningful fit to the actual ocean data. [Work supported by ONR.]
Degraded interference between direct and ground-reflected sound waves due to atmospheric turbulence
Authors: Daigle G. A. , Piercy J. E. , Embleton T. F. W.
Published: October 2005

Measurements (1–6 kHz) have been made of the interference spectrum between direct and ground-reflected waves at several distances in the range 50–150 ft from a point source 4 ft above a large asphalt surface. Simultaneously, the fluctuating values of temperature and horizontal wind speed (atmospheric turbulence) were measured at two related points close to the sound path. Previously, a theory that assumed the fluctuations in the amplitude and phase of the direct and reflected sound to be uncorrelated was fitted to similar acoustic measurements by Ingard and Maling [J. Acoust. Soc. Am. 35, 1056–1058 (1963)] using the unknown turbulence parameters as adjustable constants. Since we find experimentally that the correlation length (3–6 ft) of the meterological fluctuations is comparable to, or greater than the separation between sound paths the theory has been extended to allow for a known amount of partial correlation between direct and reflected sound. There is quantitative agreement between the degraded interference pattern calculated from the measured fluctuating meteorological variables and that measured acoustically.
Velocity of sound in supercooled and superheated water
Authors: Trinh E. H. , Apfel R. E.
Published: October 2005

We report the acquisition of what we believe to be the first experimental values for the sound speed in supercooled water down to −16.75°C under atmospheric pressure. We also present new results for the sound velocity in liquid water superheated to 160°C under atmospheric pressure [see abstract P4, J. Acoust. Soc. Am. 59, S32 (A) (1976)]. The possible extension of the data in the superheated region is the goal of some of our efforts at the present time. A prepressurization scheme described by E. N. Harvey [E. Harvey et al., J. Cell Comp. Physiol. 24, 1 (1944); 24, 23 (1944)] has been used in order to allow the liquid to undergo significant superheating. No special technique has been employed in the treatment of the water samples to be supercooled except the use of triply distilled water and the thorough cleaning of the sample container. To measure the sound speed, an ultrasonic standing wave of 2.75 MHz is established in the liquid sample contained in a 3–4 cm3 modified spectrophotometer cell. A Schlieren method allows the visualization of this standing wave and the measurement of the acoustic wavelength. The accuracy of the data is estimated to be within ± 3 m/s. [This work is supported by the U. S. Office of Naval Research.]
Standing-wave ultrasonic velocity measurements in liquids
Authors: Jarzynski J.
Published: October 2005

Recent improvements in standing-wave ultrasonic techniques have made this method particularly applicable for measurements of small changes in phase velocity. When the specimen is a liquid it is necessary to precisely correct for the effect of the transducers on the resonance frequency. Results are presented of standing-wave ultrasonic measurements in pure water at frequencies near 4 MHz. An iterative procedure for applying the transducer correction is described, which leads to an accuracy of one part in 103 for the calculated corrected speed of sound in water. Also, an estimate is made of the shift in the resonance frequency due to diffraction effects.
Extraordinary magnetoelastic coupling measured ultrasonically in Tb0.3Dy0.7Fe2
Authors: Rinaldi S. , Blessing G. V. , Cullen J. R.
Published: October 2005

We measured the magnetic field dependence of the transverse acoustic velocities in single crystal Tb0.3Dy0.7Fe2, a highly magnetostrictive material with low anisotropy. All measurements were made with the sample magnetically saturated. The field was in the plane perpendicular to [110] and containing the [001] and [110] directions. The propagation direction was [110] in all cases; the polarizations were along [001] and [1̄10]. The former is the usual configuration for determining C44, the latter for (C11 − C12). We measured reductions of 50% in the C44 elastic constant with the onset of magnetoelastic coupling (∼ 5 kOe) in this nominally cubic ferrimagnet. This is the largest such reduction ever reported for a cubic material. From the C44 variation with the magnitude of the field, we were able to determine the magnetoelastic coupling constant b2. By contrast, evidence of higher-order magnetoelastic effects was found in the 2% (C11 − C12) variation with magnetic field orientation, in accordance with magnetosfriction measurements which show that λ100 ≪ λ111. [Work supported in part by ONR.]
Two systems for measuring impedances from transducers
Authors: Cook B. D. , Cavanagh E.
Published: October 2005

Two systems for measuring impedances of transducers have been used to evaluate the properties of dynamic, piezoelectric, and magnetostrictive transducers ranging from low audio frequency to ultrasonic frequencies. One consists of a computer interfaced with a frequency synthesizer and a phase-gain meter. The other is constructed around a novel phase and quadrature detector. The computer-oriented design allows a wider frequency range and has the advantage that it is automatic; whereas, the device designed by the authors can be interfaced with normal laboratory instruments, thus reducing the cost of the system.
Performance of a condenser microphone designed for operation at elevated temperatures
Authors: Zuckerwar Allan J.
Published: October 2005

A condenser microphone system has been developed to measure pressure fluctuations at elevated temperatures. Specifications achieved with a prototype microphone are the following: maximum operating temperature (continuous duty) >427°C; harmonic distortion at 170 dB SPL = 1.4%; noise floor (22.4 Hz to 22.4 kHz) = 105 dB; frequency response (± 2 dB) = 20 Hz to 10 kHz; thermal shock, <2 dB change in sensitivity during cooling at rate of 162°C/min; vibration sensitivity <0.5 Nm−2/g. The three predominant effects of temperature changes are changes in the membrane—backplate gap, membrane tension, and air viscosity. The microphone is designed so that changes in gap and membrane tension tend to have compensating effects upon the microphone sensitivity. [Work supported by NASA Grant NSG-1039.]
Design of transducers for multiple-frequency operation
Authors: Auyer S. E. , Winnicki R. T.
Published: October 2005

Use is frequently made of a λ/4 mechanical impedance matching section on the face of a transducer to improve coupling of acoustic energy from the transducer into the medium and to increase operating bandwidth of the transducer. It is shown that the addition of this matching section introduces additional, higher-frequency, resonances in the transducer. By proper design of the transducer and matching section, the resonances can be independently controlled as to frequency and operating bandwidth so as to result in a device capable of operation at multiple, widely-spaced, frequencies.
New approach to a constant beamwidth transducer
Authors: Van Buren A. L. , Rogers Peter H.
Published: October 2005

The theory of a broadband constant beamwidth transducer which is to be used primarily as a projector is presented. The transducer is a spherical cap of arbitrary half-angle α shaded so that the normal velocity is given by ur = u0Pv(cosθ), where Pv is the Legendre function whose root of smallest angle occurs at θ = α. The required value for v can be obtained to within 1% for α ⩽ 1 rad from the approximation v ≃ 0.5(4.81/α − 1). The transducer is shown to have uniform acoustic loading, extremely low side lobes and an essentially constant beam pattern for all frequencies above a certain cutoff frequency. Under piezoelectric drive the transducer is shown to have a flat transmitting current response over a broad band.
Third sound: a study of the superfluid-helium film
Authors: Telschow K. L.
Published: October 2005

Liquid-helium films of only a few atomic layers thickness exhibit a remarkable mobility as a result of the condensed superfluid state. The atoms are tightly bound to the substrate surface by the van der Waals attraction leaving almost complete freedom of motion in the lateral directions. Disturbances in the film thickness then propagate as waves called third sound. A wealth of information concerning the static and dynamic properties of the film have come from third-sound group-velocity measurements primarily through detecting small temperature oscillations accompanying the wave. We have learned that these waves can propagate in essentially monolayer films thus exhibiting a two-dimensional superfluid. A very important quantum-mechanical length describing the coherence of the condensate atoms is now known from static third-sound velocity measurements. Experiments on the Doppler shift of flowing films have delineated the superflow phase region. Recently experiments have demonstrated the potential flow nature of the film and measured its ability to trap circulation. Subsequent measurements of the decays of these persistent currents are yielding new insights into the general stability of the superflow state.
Parametric generation of sound by resonant mode conversion in helium II
Authors: Garrett Steven , Putterman Seth , Rudnick Isadore
Published: October 2005

When nonlinear effects are included, the two fluid hydrodynamic description of superfluid helium possesses solutions which couple first and second sound. Resonant conversion of two second-sound waves into a first sound wave is calculated. An experiment to observe this effect is currently under construction and will be described. [Work supported by ONR and NSF.]
Acoustics of mallet percussion instruments
Authors: Rossing Thomas D.
Published: October 2005

Mallet percussion instruments generally employ tuned bars with free ends as sound sources. These bars vibrate in many modes, emitting overtones which are generally not harmonic of the fundamental, thus giving mallet percussion instruments their distinctive timbres. Glockenspiel or orchestra bells employ rectangular steel bars, and striking them with hard mallets excites both flexural and torsional modes. Xylophone bars, of rosewood or epoxy, are commonly shaped so that the first overtone is a musical twelfth above the fundamental. Bars of marimbas and vibes, in the low and midrange, have their first overtone tuned two octaves above the fundamental. Marimbas, xylophones, and ribes are usually fitted with tubular resonators which increase the efficiency of sound radiation at the fundamental frequency. Chimes or tubular bells are designed to ring with a bell-like timbre. Triangles, because of their many audible overtones, are usually characterized as having an indefinite pitch. Modes of vibration and sound spectra of each of these instruments are discussed in detail.
Suppression of bell warble
Authors: Perrin R. , Charnley T.
Published: October 2005

The causes and possible methods of suppression of warble in bells are reviewed. The results of applying a new technique, recently proposed by the authors, are reported.
Architectural acoustics and sound system experience in the Seattle Kingdome
Authors: Paoletti D. A. , Lewitz J. A.
Published: October 2005

The King County Domed Stadium opened on 27 March 1976. The stadium seats 80 000 for shows, 65 000 for football, and 59 000 for baseball in a space with enclosed volume of over 50 000 000 ft3. The methods of reverberation control will be discussed and illustrated with particular emphasis on structural and budgetary constraints. Prior to the opening, acoustical tests were conducted using the sound system to determine speech intelligibility. The results illustrate the importance of maximizing the ratio of direct to reverberant sound to achieve the best speech intelligbility at a listener position. Some special aspects of the sound system operation are discussed along with the performance characteristics of the installed system. [Architect/Engineers: Narramore Skilling Praeger, Joint Venture. The authors were principal consultants for this project while employed at Bolt Beranek and Newman, Inc.]
Design, development, and field testing of a stable sound source for privacy testing between dwelling spaces according to ASTM Recommended Practise 597
Authors: Barron Kenneth E. , Rivard Marcel T.
Published: October 2005

The new ASTM Recommended Practise 597 for testing of privacy between dwelling spaces requires an accurate, calibrated, and stable sound source employing specially shaped source and absorption frequency spectra. This paper describes the sound source, its circuitry, electrical and acoustical performance as well as field experience during testing sessions. In addition to providing the special spectra, the remote, radio-controlled source provides several other spectra and functions frequently used by persons involved in acoustical testing.
Music building for a small liberal arts college
Authors: Kingsbury Howard F.
Published: October 2005

Lebanon Valley College, Annville, PA has had a strong music program for many years. Recently it felt the need for new facilities to complement the program. The new building was occupied in the fall of 1975. It contains a 400-seat recital hall, band room, organ-choral room, faculty offices and studios, classrooms, and individual and group practice rooms. The building was designed by Bogar and Bink, Lemoyne, PA. The acoustical consultant was engaged early in the planning process. This made possible a high degree of interaction between the architect and consultant throughout the planning, design, and construction process. This paper reviews the acoustical design considerations and solutions to the many room acoustics, sound isolation, and mechanical system noise control problems typical of a music building. Measured data on ambient noise and room-to-room noise reduction will be shown, in comparison with the design criteria. One unusual feature of the recital hall is the methodology of varying easily the hall reverberation time for small and large group performances. Measured reverberation times versus calculated will be shown.
Scintillations of sound propagating through the turbulent atmosphere
Authors: Gonter Robert H.
Published: October 2005

During the Haswell Experiment sponsored by NOAA's WPL in March 1974, sound propagating from a source on a 150-m tower was received on the ground at slant range of 188 and 333 m. Recordings were made using a tetrahedral array 1 m on a side at frequencies of 500 and 1000 Hz. Using time delays between three pairs of microphones, direction cosines were computed for a plane wave arriving at the array. The cosines indicate that the direction of the sound reaching the array fluctuates several degrees in direction during medium turbulence at 188-m distance. Computed sound source direction misses the actual source direction by about 12° in the vertical and 5° horizontal at 188 m for both 500 and 1000 Hz. At 333 m, noise and loss of signal prevented computing reliable source direction.
Acoustics of motocycle helmets
Authors: Van Moorhem W. K. , Shepherd K. P. , Magleby T. D. , Torian G. E.
Published: October 2005

Motocycle helmets both act as a source of aerodynamic noise and attenuate external sounds. These facts have been the basis of some arguments concerning accident avoidance while wearing a helmet. In the present study measurements of at-ear helmet-generated aerodynamic noise and helmet transmission loss were carried out. From these data and existing information on at-ear noise levels generated by air flow about a bare head, a comparison of the ability of bare-headed and helmet wearing motocyclists to detect external acoustic signals was carried out. It was found that under no conditions did a properly fitting helmet put its wearer at a disadvantage to the bare-headed rider, and at typical speeds the helmet gave a considerable advantage.
Assessment of the noise environment in locomotive cabs
Authors: Kilmer Roger D. , Blomquist Donald S.
Published: October 2005

The National Bureau of Standards has developed an instrumentation system for assessing the noise environment in locomotive cabs for the U. S. Department of Transportation, Federal Railroad Administration. This measurement system is comprised of three basic subsystems: (1) two seat-mounted stationary microphones located approximately 20 cm from each ear for the engineman and brakeman; (2) a remote noise detection system consisting of a lapel mounted microphone and telemetry transmission and reception systems for both crew members; and (3) an operational parameters system to enable study of the operational duty cycle. After signal conditioning the data from each of these subsystems are recorded on magnetic tape. The information obtained from this assessment is in a form such that the total noise exposure or “dose” of each of the crew members can be determined. For diagnostic purposes, the measurement techniques utilized provide: a means of identifying individual component sources and specific locomotive operations which might contribute to the noise levels in the locomotive cab; and a procedure for estimating their relative contributions to the total noise “dose.” Preliminary data obtained with the use of this system will be presented.
Cochlear potentials of the pigeon: relationships to age, serum cholesterol level, atherosclerosis, and blood coagulation factors
Authors: McCormick James G. , Hartley C. Bryce , Ens Gordon E. , Merritt William
Published: October 2005

Previously we reported [J. G. McCormick, R. M. Clayton, and I. L. Holleman, J. Acoust. Soc. Am. 52, 193 (1972)] that round window cochlear potentials of old pigeons that developed spontaneous carotid atherosclerotic plaques were poorer in sensitivity than younger birds of the same breed with little or no evidence of plaques. We also noted that a high cholesterol diet fed to these birds was correlated with a reduction of cochlear potentials. This initial work, which included studies on birds genetically resistant to atherosclerosis was a pilot project on 75 birds. In our present paper we will report further findings from a one year study of over 220 additional atheroselerotic pigeons. The age relationship to cochlear potential loss is substantiated, and correlative sophisticated blood coagulation tests will be discussed. [Work supported by NIH Grant No. NS-12013 and Bowman Gray School of Medicine, Venture Capital Grant No. 2-156-801-2507.]
On the source of the scalp recorded auditory frequency-following response (FFR)
Authors: Hou S. M. , Lipscomb D. Mo
Published: October 2005

Comparisons were made of CM and FFR recorded from chinchilla with various electrode placements. The latency of the scalp/ear lobe recorded FFR was found to be nearly zero with respect to CM. Further, AP and SP were noted to diminish rapidly after death whereas the CM component in FFR reduced gradually. The decay of the CM component of FFR measured at the scalp after death followed an identical time course to that of the CM at the round window. These observations lead to the conclusion that FFR does not originate in the brain stem but is essentially cochlear potentials picked up by electrodes located at the scalp. Relation of these controversial findings to the existing literature will be discussed.
Amplitude-spectrum representation of acoustic signals in the primary auditory cortex of the mustache bat
Authors: Suga N. , Manabe T.
Published: October 2005

The mustache bat (Pteronotus parnellii rubiginosus) emits orientation sounds containing a long constant-frequency (CF) component suited for echo-detection and Doppler-shift measurement. About 30% of the primary auditory cortex of this bat is chiefly devoted to processing the CF-component in Doppler-shifted echoes. In this “Doppler-shifted—CF-processing area,” single neurons recorded in any electrode penetration orthogonal to the cortex have identical best frequencies (BFs) and best amplitudes (BAs) at which the neurons show maximum excitation. The BF and BA systematically vary with the location of the neurons in the cortex, showing tonotopic and “amplitopic” representations. The representation axes are radial and eccentric, respectively. The amplitude spectrum of an acoustic signal, that is, both the relative velocity and subtended angular information about a target is thus represented in the coordinates parallel to the cortical surface. This amplitude-spectrum representation is disproportionate, projecting an echo with more perceptual significance to a larger area. Outside this Doppler-shifted—CF-processing area are found neurons specialized for responding to a particular information-bearing element or a particular combination of information-bearing elements in orientation sounds and echoes. [Work supported by NSF.]
Detection of sinusoids in multiple narrow-band noise
Authors: Smith S. M. , Taylor M. M.
Published: October 2005

500-msec soft-gated sinusoidal signals were masked by one, four, or eight independently generated 50-Hz noise bands centered in separated critical bands, at 640, 1000, 1390, and 1740 Hz. The single-band noise was made by presenting one of the frequencies either monaurally or binaurally (diotically), the four-band used all four frequencies binaurally, and the eight-band used the four frequencies dichotically. The signal uncertainty on different runs of 80 trials was varied from a single monaural or binaural frequency held constant over the run, to a new choice for each trim from the set of noise-band center frequencies used on that run. Performance was disrupted both by increasing the number of independent noise bands while keeping the signal frequency known, and by increasing the number of possible signal frequencies or ear presentations while holding the noise constant. The 8-signal in 8-noise (8S8N) task was 4.1 dB more difficult than the 1S1N task. Half the decrement could be attributed to adding noise bands, and half to signal uncertainty. Since the noises were separated by more than one critical band, simple masking cannot account for the effect of the added noise bands.
Binaural critical masking bands
Authors: Sever J. C. , Small A. M.
Published: October 2005

Current understanding of the relation between monaural estimates of the critical bandwidth for masking and those obtained in binaural listening situations is poor. The present study was designed to improve this situation by obtaining estimates of critical bandwidth when the signal and masker were presented (1) monaurally, (2) binaurally with both signal and masker in phase at the ears, and (3) binaurally with masker in phase and signals 180° out of phase. Threshold estimates were obtained in a two-interval forced-choice paradigm as a function of masker bandwidth for signal frequencies of 500 and 2000 Hz for the three conditions mentioned above. Maskers were computer-synthesized and had essentially infinite rejection slopes. For both signal frequencies, the derived critical bandwidth estimates for the monaural condition and the binaural in-phase condition were equivalent. These values were 60%–70% of the critical bandwidth estimates obtained in the binaural condition with the masker in phase and the signals 180° out of phase.
Effects of duration and interaural delays of masking noise on detectability under homophasic and antiphasic signal conditions
Authors: Trahiotis C. , Hanna T. , Bernstein N.
Published: October 2005

Detectability of a 500-Hz tone of either 10 or 100 msec duration in broadband 50-dB spectrum-level noise of identical duration was measured as a function of the interaural delay of the noise. Homophasic or antiphasic signals were presented in a single-interval, forced-choice task employing five randomly presented signal levels. In coherent noise (1) equal energy homophasic signals were equally detectable regardless of noise duration; (2) antiphasic signals were more easily detected than their homophasic counterparts; and (3) antiphasic signals in the 10 msec condition required 6 dB more energy for performance to equal that found in the 100-msec antiphasic condition. Detectability in the 100-msec conditions decreased slowly as a function of time delay and signal conditions provided data which interleaved in a well-known manner [T. L. Langford and L. A. Jeffress, J. Acoust. Soc. Am. 36, 1455–1458 (1964)]. However, the data gathered in the 10-msec conditions revealed severe degradation in the observer's ability to process signals in noises delayed interaurally from 1 to 5 msec.
Forward masking effects of nonwaveform stimulus change
Authors: Friedman C. , Pastore R. E.
Published: October 2005

Our laboratory's recent work on the nature of masking has revealed that stimulus change can cause both forward and backward maskinglike effects. In these previous demonstrations, a decrease or shift in the noise contained in the signal channel constituted the stimulus change. To demonstrate that these masking effects were attributable to stimulus change and not the interaction of off-frequency transients, we designed the present experiment in which the stimulus change occurred in the nonsignal ear. In this case, stimulus change consisted of a shift in correlation of the noise between the two ears by inverting the contralateral noise at various times (4 < Δt < 200 msec) prior to the onset of the potential signal. Relative to the unchanging (+1 or −1) contralateral noise control conditions, the detectability of the signal was significantly decreased independent of the direction of change in correlation (+1 to −1, or −1 to +1). Effects of differing rise-fall times (1, 2.5, and 5 msec) of noise change were also examined. The results are discussed in terms of current masking theory. [This research was supported by a grant from NINDS.]
Contemporary uses of electronic music synthesizers in pop music
Authors: Gleeson Patrick
Published: October 2005

I will play taped excerpts from various recordings I have contributed to as a synthesizer player and arranger. The recordings span the period from 1970 to the present, by “charted” (top 200) artists, such as Jefferson Starship, Lenny White, Dr. Hook, Pablo Cruise, and Herbie Hancock. I will discuss each selection and in some cases will present the tracks in various special mixes which will make clear the role of the synthesizer. My general purposes are (1) to relate contemporary practice among pop recording artists; (2) to discuss certain limitations of contemporary instruments, emphasizing those that may be particularly interesting to the members of the Acoustical Society; and (3) to point out some unexplored directions which might be taken for users of this wonderful musical instrument.
Performance values in studio realizations of electronic music
Authors: Carlos W. , Elkind R.
Published: October 2005

Working techniques and philosophy for our particular approach in producing electronic music recordings will be discussed. The studio facility will be discussed, particularly its unique features. An example of a typical complex musical passage will be played in component and find forms. We also will attempt to cover several mixing situations in which both quad and stereo “imaging” may be made to simulate that of a natural acoustic environment.
Cochlear distortion-products: effects of altering the organ of Corti
Authors: Siegel J. H. , Kim D. O. , Molnar C. E.
Published: October 2005

We have extended the cat studies of Kim and Molnar [Neuroscience Abstracts Vol. II, 1976] to the chinchilla with normal or altered organ of Corti. As in the cat, propagated distortion-products (f2−f1) and (2f1−f2) are strongly present in responses of normal chinchilla cochlear-nerve fibers. Exposure of chinchillas to a 4 kHz octave-band noise at 108 dB SPL rms for two hours produced destruction of the organ of Corti in the basal two-thirds of the cochlea. Two-tone pairs with f1=3680 Hz and f2=4000 Hz, corresponding to the damaged region, produced no measurable propagated distortion-products; two-tone pairs with lower frequencies corresponding to the undamaged region produced large propagated distortion-products. In normal chinchillas, brief (1–2 min) exposure to an 80–90 dB SPL single-frequency fatiguing-tone, similar in frequency to the two-tone pairs, led to a temporary reduction, by more than half, of the amplitude of the propagated distortion-products; recovery was complete in a few minutes. We conclude: (1) Propagated distortion-products are generated in the cochlear region where both primary components are large, and then mechanically propagated apicalward like externally applied single tones; (2) even delicate and reversible alterations of the organ of Corti can affect the strongly-nonlinear behavior of the motion of the cochlear partition. [Work supported by NIH Grants NS07498, RR00396, NS07057, and NS00162.]
Effects of spectral complexity of contralateral cueing on signal detection during backward masking
Authors: Puleo J. S. , Pastore R. E.
Published: October 2005

In a single-interval (yes-no) detection paradigm identical to that employed previously [J. S. Puleo and R. E. Pastore, J. Acoust. Soc. Am. 60, S49 (A) (1976)], we investigated the extent to which contralateral cues of various spectral complexity could improve signal detectability during monotic backward masking in the presence of a second, continuous masking noise. We used a 20-msec segment of a 500 Hz sinusoid as the signal and a burst of band-limited noise (100 to 800 Hz wide) centered at the signal frequency as the cue. Results showed that, relative to the noncued condition, significant reductions in backward masking occurred regardless of the type of cues employed. Although the narrower-band cues were somewhat more effective in reducing backward masking than the wider-band cues, these differences were not behaviorally significant. None of the cues were very effective in reducing simultaneous masking. These results are discussed in terms of their theoretical implications regarding the nature of backward masking. [This research was supported by a grant from NINDS.]
Measurement and analysis techniques for the description of palatal shape
Authors: McCutcheon Martin J. , Hasegawa Akira , Fletcher Samuel G.
Published: October 2005

Descriptions of the spatial features of linguapalatal contact during speech production require accurate measurement of the shape of the palatal surface and location of contact electrodes. A technique is described for three-dimensional measurements utilizing stone models cast from impressions of a speaker's mouth. Measurements of the coordinates of points on the surface of the maxillary molars allow the calculation of a reference plane analogous to the occlusal plane derived from lateral x rays. Measured coordinate values with respect to this plane are used in an orthogonal function analysis to obtain parameters for the palatal surface description. Typical results and applications are illustrated and discussed. [Supported by NIH Grant NS-11852-01A from NINDCDS.]
Acoustic reasons why labio-velars are both labials and velars
Authors: Ohala John J. , Lorentz James
Published: October 2005

The phonological literature reveals an interesting asymmetry in the behavior of labio-velar speech sounds, i.e., w, u, kp, gb, etc., namely, that when nasalized or determining the place of articulation via assimilation of adjacent nasal consonants, they behave primarily like velars not labials, whereas when they become fricativized or determine the place of articulation of adjacent fricatives, they behave primarily like labials, not velars. The reasons for this will be explained by reference to well-known principles of acoustic phonetics. It will be shown that for nasals the most important of multiple oral constrictions is the rear-most constriction whereas in the case of fricatives it is the front-most constriction which is most important in determining the characteristics of the output sound. This case is offered as another example of the application of physics to philology. [Supported by National Science Foundation.]
Experimental investigation on sound transmission through cavity-backed panels
Authors: Barton C. Kearney
Published: October 2005

A considerable amount of information has been developed in architectural acoustics on sound transmission through panels. Emphasis has been on high-frequency transmission where “mass law” is applicable and coincidence effects are important. However, there has been only limited attention given to low-frequency sound transmission. Low-frequency sound transmission is stiffness controlled in the frequency region below structural resonances, and damping and stiffness controlled at resonances. Furthermore, the closed receiving room (cavity) behind the panel may have a significant effect on the panel dynamics and, therefore, the sound transmission. A panel backed by a closed cavity provides a meaningful model for studying low-frequency sound transmission of the type encountered in aircraft for example. Although some theoretical work has been done on the subject, only limited experimental data are available in the literature. The purpose of this paper is to present some experimental findings on the effects of panel stiffness and receiving space absorption on low-frequency sound transmission through panels into closed spaces. In addition, a simplified method for calculating the low-frequency noise reduction of a cavity-backed panel will be presented.
Comparison of reverberation measurements using Schroeder's impulse method and a decay-curve averaging method
Authors: Chu W. T.
Published: October 2005

Utilizing a digital acquisition system and minicomputer, two promising techniques for accurate determination of reverberation times have been studied in detail from the viewpoint of standard reverberation room tests. The first is Schroeder's “integrated impulse method”; special attention was given to the question of repeatability and the influence of signal-to-noise ratio on the successful application of the method. The second technique involves taking an ensemble average of a large number of the logarithmic decay curves. It was found that even for nonuniform decays, the averaged decay curves obtained by the second method compared well with those determined by the “integrated impulse method.” Some of the advantages and disadvantages of both methods will be discussed.
Computing the modulation transfer function and the intelligibility score for rectangular enclosures
Authors: Plomp R. , Steeneken R. J.
Published: October 2005

Assuming geometrically perfectly reflecting walls and ceilings and assuming some further reasonable simplifications the modulation transfer function (MTF) for any speaker—listener pair in a rectangular room can be calculated. Earlier research [cf. T. Houtgast, Acustica 28, 66–73 (1973)] has demonstrated a close relationship between a weighted version of this MTF and the PB-word score as a measure of speech intelligibility. The effect of noise in the room has been included in the equations by considering the audience as a collection of individual noise sources. The theory appears to be in good agreement with some rules (benefit of reflections arriving within about 50 msec; optical reverberation time; intelligibility score as a function of distance) based on experience. The results of some additional computations illustrating the predictive power of the theory will be presented. They include: which walls should preferably be provided with sound-absorbing materials; effect of position of speaker, or symmetry of wall treatment, on the contours of equal intelligibility.
Effects of reed resonance on woodwind tone production
Authors: Thompson S. C. , Benade A. H.
Published: October 2005

In normal woodwind tone production the nonlinear flow control properties of the reed transfer energy between the harmonies of the spectrum, and the favored playing frequency is one for which the air-column input impedance is high at several harmonics. Above the middle of the second register woodwinds have only one participating impedance peak; yet these notes can be played even without the use of a register hole, despite competing possibilities of low-register intermode cooperation. Such notes are possible because enhancement of the reed's transconductance A near its own resonance frequency can offset the small input impedance Z of the air column so that (ZA − 1) > 0, providing an additional means for energy production above cutoff. Since Z and A do not appear symmetrically in the complete description of the system, the spectral relations deduced by Worman do not apply when reed-resonance effects are important. Musicians exploit the possibility of matching the reed resonance to a harmonic of the playing frequency in the upper two registers since the tone is stabilized in loudness, pitch, and tone color. The measured sound spectrum component at the reed frequency is then enlarged, as are the adjacent components produced as heterodynes with the fundamental.
Violas from twelve to twenty inches
Authors: Hutchins Carleen M.
Published: October 2005

The normal range for the body length of the viola is usually considered to be between 16 and 17 in. When an instrument is shorter than this, 15 to 16 in., most violists consider it a small viola; and when longer than this, 17 to 18 in., an extra large one. During the 1950's, Frederick A. Saunders and I explored the possibilities of moving the main wood and air resonances of the viola around the expand this range. First in a 12-in. viola utilizing the so-called subharmonics of both the main air and wood resonances; and second in the 20-in. viola where the main air and wood resonances are in a similar position to those of the normal violin, These two instruments have been developed and explored musically over the last 15 years. They will be demonstrated and discussed acoustically in comparison to the normal viola.
Vibrational energy transfer in a diesel engine
Authors: DeJong R. G. , Lyon R. H.
Published: October 2005

The paths of vibrational energy transfer in a diesel engine were investigated in order to obtain insight into ways of reducing this transfer to the exterior surfaces and thereby reduce the radiated noise. The engine was tested in a nonrunning condition with simulated internal forces in order to study the different transfer paths separately. Vibration response measurements were made of individual engine components and lumped-parameter models were developed to simulate this response. These models were then used to determine component design changes that would reduce the energy transfer. Two design changes were implemented in the engine and a reduction of the energy transfer was achieved as predicted.
Amplitude response of finite plates and the characteristic admittance theory
Authors: Williams Earl , Skudrzyk Eugene
Published: October 2005

Frequency response curves of rectangular plates and of plates of different shapes will be presented and the results compared with the predictions of the Characteristic Admittance Theory. Regardless of the point of excitation, the mean line through the driving-point response curve seems to always coincide with the predicted mean line as closely as this line can be drawn. The accuracy is not quite as great if the driving point and the point of observation are separated. [Work supported by ONR, Task No. 064-475.]
Sound radiation from an elastically supported circular plate
Authors: Suzuki Hideo
Published: October 2005

The sound radiation from an elastically supported circular plate in an infinite baffle, which is excited by a concentric voice coil, was discussed taking account of the reaction of the acoustical fluid. Eigenvalue, elgenfunction, and volume velocity of each mode of the plate with different edge stiffness were calculated. It was found that the effect of elasticity was smaller for higher order of modes. There was a remarkable difference between the frequency response curves for light and heavy loading. For light loading(air), the peaks and dips were the results of resonances between the mass of the voice coil and the reactance of the mechanical impedance of the plate. On the other hand, for heavy loading(water), peaks and dips occurred when the reactance of mechanical impedance of the plate and radiation impedance canceled each other. The effect of several factors such as the loss factor of the plate, the mass and the radius of the voice coil on the frequency response curves were also discussed.
Impulse response spectral characteristics and acoustical shadowing in rough-surface backscattering
Authors: Novarini J. C. , Medwin H.
Published: October 2005

The boundary diffracted-wave technique which takes account of the reflected and diffracted waves scattered from a plane strip [A.W. Trorey, Geophys. 35, 762–784 (1970)], [C.S. Clay, J. Acoust. Soc. Am. 58, S67 (A) (1975)] has been extended with the objective of determining the acoustical shadowing caused by crests of rough ocean surfaces during backscattering. Our computer analysis yields the impulse and spectral response of model surfaces and avoids most of the assumptions and approximations that have characterized previous studies of rough surface scattering. [Work supported by the Office of Naval Research and the Research Council of the Naval Postgraduate School.]
Spatial correlation of target echoes generated by bionic signals
Authors: Piemons T. D. , Moravan K. Y.
Published: October 2005

The signal-processing capability of an animal sonar system such as that of the porpoise may be dependent on the spatial correlation of both the target echo and the background interference. In a computer simulation study, digital echo wave-forms at two spatially separated receivers were computed for targets modeled as a spatial distribution of point reflectors. Wide-band signals similar to those employed by the Atlantic bottlenose porpoise were used. The dependence of the spatial correlation of the echo on receiver separation, frequency, bandwidth, and target geometry is discussed. [Work supported by the Naval Sea Systems Command.]