bluuebunny/crossref_metadata_2025 huggingface dataset:
Capacitance microphone static membrane deflections: Comments and further results
Authors: Warren J. E.
Published: October 2005

The biasing of capacitance microphones by a constant voltage or electret charges places electrostatic forces on the microphone’s membrane diaphragm. Due to the dependence of the electrostatic forces on the deflections, the final membrane position is governed by a nonlinear differential equation. Because of this nonlinearity, certain ranges of the parameter values exist for which stable static deflections cannot be obtained. Numerical methods are usually used to obtain the deflections and their critical or highest stable values. The results of two past investigations using different forms for the nondinemsionalized nonlinear differential equation are reviewed and compared [Warren et al., J. Acoust. Soc. Am. 52, 711–719 (1972); Friam et al., J. Acoust. Soc. Am. 53, 1601–1608 (1973)]. A third, and perhaps more appropriate, form for the nondimensionalized differential equation is presented and discussed. Using this third form, deflection and stability results are reviewed for circular and annular membranes. Recent results are then presented for rectangular strip membranes with the tension applied along one axis and supported only on the edges perpendicular to that axis. In general, annular membranes are more stable than the other two types of membrane systems. The effect of openings in the stationary electrode was found to increase the stability in all three types of membrane systems. The amount of increase was found to be dependent upon the size and location of the openings. The static deflections and their stability values are of importance since they determine the operating position of the membrane diaphragm and the operating range of many microphone parameters. Application of the stability results to membrane switches may also be possible [Sessler et al., IEEE Trans, Commun. COM-21(1), 61–65 (Jan. 1973)].

Subject Classification: 85.44, 85.62.
Responses of single units in the cochlear nucleus of the cat to cosine noise
Authors: Bilsen F. A. , ten Kate J. H. , Buunen T. J. F. , Raatgever J.
Published: October 2005

The response of single cells in the cochlear nucleus of the cat to noise with a cosinusoidal power spectrum (cosine noise) was studied. Cosine noise is obtained by adding white noise to the same noise delayed over a time τ; maxima in the spectrum occur at n/τ (n=0,1,2,⋅⋅⋅). The spike rate of a unit was continuously registered as a function of τ (τ diagram). This registration shows a periodic fluctuation having maxima at τ=n/CF and troughs at τ= (n+1/2)/CF, with a decreasing peak–trough ratio for increasing n (CF is the characteristic frequency of the unit). For the majority of the units investigated, a maximal peak–trough ratio was observed not for n=0 but for about n=3. This is ascribed to lateral inhibition. By introducing the mathematical concept of a weighting function in the frequency domain, a quantitative relation with the response of the unit to a pure tone in white noise (iso-intensity curve) could be established. The results are compared with psychophysical results on the internal representation of cosine noise. Possible implications for the existence region of (repetition) pitch and the phenomenon of spectral dominance are discussed.

Subject Classification: 65.44, 65.40.
Fast beamforming techniques for circular arrays
Authors: Farrier D. R. , Durrani T. S. , Nightingale J. M.
Published: October 2005

This note describes a technique for beamforming on circular arrays which exploits the array geometry to facilitate the use of FFT techniques, and this leads to substantial saving in computing effort. The algorithm described here is particularly advantageous for systems employing a large number of sensors.

Subject Classification: 60.30.
Ultrasonic registration of the fundamental frequency of a voice during normal speech
Authors: Holmer Nils-Gunnar , Rundqvist Hans Erik
Published: October 2005

A continuous wave of ultrasound through the larynx is used to determine the fundamental frequency of the vocal folds during normal speech. The variation of the ultrasound intensity transmitted between two matched transducers through the vocal fold level is recorded. The apparatus used for these recordings is described. Different transducer positions are investigated and, further, the transducer geometry is discussed.

Subject Classification: 70.20; 80.45.
Comparison of cube-textured and conventional nickel magnetostrictive ring transducers during low-power linear drive
Authors: Huston E. Lee , Sinsky Joel A.
Published: October 2005

The magnetic and magnetostrictive properties of a scroll-wound ring transducer made from cube-on-face-textured nickel were measured and compared to the corresponding properties of a conventional Nickel 200 ring transducer. Both transducers were separately excited in air at low-power linear drive levels with varying levels of bias induction, and their electrical input impedances were measured. Some in-water measurements were also made on the two rings at nearly optimum values of bias induction. Nickel 200 exhibits larger μT33 and d33 values at all induction levels, while the textured nickel shows larger k33 and g33 values. The data obtained can be used to choose the type of ring and bias induction level of operation which will best satisfy a given requirement.

Subject Classification: 85.46.
Reverberation from plankton at 330 kHz in the Western Pacific
Authors: Castile Brett D.
Published: October 2005

Acoustic volume reverberation was observed in the open ocean at a frequency of 330 kHz and a depth of approximately 20 m. The instantaneous scattering volumes were small, ranging in size from 0.2 to 0.9 m3. The reverberation was observed primarily as an incoherent return from multiple scatterers (probably greater than 10/m3) but there were also discrete echoes of duration equal to that of the transmitted tone burst, 1 msec. The backscattering strength of the water calculated from the incoherent reverberation was independent of the time of day and varied from about −86 dB relative to 1 m−1 down to −96 dB and is surmised to be due to phytoplankton. The discrete echoes were more numerous at night than during the day and were produced by scatterers most of whose target strengths were on the order of −94 to −86 dB, approximately what would be expected of the small zooplankters such as copepods which were present.

Subject Classification: 30.40, 30.30.
Author’s reply to ’’Comments on ’Measured jet noise compared to California noise codes and health limits’ ’’ [B. G. Hildebrand, J. Acoust. Soc. Am. 58, 1323–1325 (1975)]
Authors: Lane S. R.
Published: October 2005

B. G. Hildebrand’s criticisms of my paper are based on faulty analyses which invalidate the conclusion that my results are ’’unsupported.’’ He ignores the lateral distance factor in the FAA/NAFEC data and the Inglewood data-system limitations, and thus does not make the proper comparisons to the California noise limits or to the peak noise directly beneath the aircraft. The fact that the NAFEC approach noise data were generally less than the legal limit in the 1 mile from threshold region may be attributed to the use of nonstandard noise abatement flight procedures. The additional Inglewood data he shows in his Fig. 1 are not valid indicators of the peak noise levels since the range setting of the measurement system extended to only 100 dBA (i.e., noise peaks above 100 dBA were attenuated). The physical relations of noise source strength and attenuation with distance indicate that my jet aircraft approach noise measurements in the 1 mile from threshold area at LAX were entirely consistent with the Inglewood data measured farther out in the 3 miles from threshold area.

Subject Classification: 50.50, 50.75, 50.55.
Encoding and pitch strength of complex tones
Authors: Hall Joseph W. , Soderquist David R.
Published: October 2005

Pitch perception in the human was examined with respect to the level of neural analysis and pitch strength of various complex tones. In binaural conditions, three-component complex stimuli were presented to each ear in such a way that if a central processor determined pitch from the combined information from the two ears, one pitch would be perceived. If the pitch processor attended to the information from each ear separately, two pitches would be perceived (corresponding to the fundamental at each ear). Two pitches were perceived and the importance of peripheral encoding for pitch perception was supported. Subjects judged the strength of monaurally and binaurally presented stimuli as a function of the spectral region of the frequency components, number of components per complex, and the spacing between components. Pitch strength was discussed in terms of recent theoretical models of pitch.

Subject Classification: 65.54, 65.56, 65.62.
Input–output functions of cochlear whole-nerve action potentials: Interpretation in terms of one population of neurons
Authors: Özdamar Özcan , Dallos Peter
Published: October 2005

It is commonly assumed that the two-segmented input–output functions of the whole-nerve action potential are a result of the activity of two sets of primary fibers: a low- and a high-sensitivity group. While anatomical studies show the existence of two populations of fibers, there are no clear-cut electrophysiological signs of two distinct populations responding with different thresholds. In light of this physiological result, it is desirable to construct a scheme for the growth of the whole-nerve action potential that involves only one group of fibers. This can be done in a qualitative fashion by considering the pattern of single-unit tuning curves and assessing the contribution of populations of units to the compound response. Thus the slowly growing low-level segment of the input–output function is identified with the sharp tip region of the tuning curves of the responding units, while the high-level, rapidly growing, segment is associated with the recruitment of higher-frequency units that respond on the tail segment of their tuning curves. Thus the low and high parts of the input–output functions are interpreted in terms of the excitation of narrow and wide segments of the cochlear receptor. Masking experiments that support the scheme are described.

Subject Classification: [43]65.35, [43]65.42, [43]65.59, [43]65.40.
Two-tone suppression in auditory-nerve fibers: Extension of a stimulus-response relationship
Authors: Abbas Paul J. , Sachs Murray B.
Published: October 2005

Average discharge rate of single auditory-nerve fibers in cats was measured in response to one- and two-tone stimuli. One component (the ’’suppressor tone’’) of each two-tone stimulus was at a frequency (f2) which produced two-tone suppression at some stimulus levels. The other component (excitor tone) produced an increase in rate above the spontaneous rate when presented alone. Fractional response was defined as the driven rate to the two-tone stimulus divided by the driven rate to the excitor alone. Fractional response is thus a quantitative measure of the amount of suppression produced by a suppressor tone. A number of qualitative differences were found in the dependence of fractional response for f2≳CF and f2<CF. For suppressor tone frequencies greater than CF, fractional response depends only on the ratio of suppressor to excitor levels (P2/P1) for a range of excitor levels (P1). For P1 large enough to drive a unit into saturation, fractional response increases with P1. For f2<CF, however, fractional response is a monotonic decreasing function of P2 and P2/P1; it is also a monotonic decreasing function of P1 for P2/P1 fixed. Consistent with these results if the tone level ratio P2/P1 is fixed, rate is a monotonic increasing function of the overall level of a two-tone stimulus for f2≳CF; for f2<CF, rate is typically a nonmonotonic function of overall level. For f2≳CF, slopes of (log) fractional response versus (log) P2/P1 curves are a monotonic decreasing function of suppressor frequency f2. For f2<CF, on the other hand, slope does not depend on f2. If f2 is fixed, and excitor-tone frequency (f1) varied, fractional response decreases with f1 for f2≳CF; for f2<CF, fractional response is independent of f1.

Subject Classification: [43]65.42, [43]65.59.
Equal-sensation functions generated by the method of magnitude estimation
Authors: Stevens Joseph C.
Published: October 2005

The method of magnitude estimation has been adapted to measure successfully various kinds of equal-sensation functions in several sense modalities. These successes may help to evaluate a recently reported severe failure of the method to yield satisfactory duration-intensity trading functions for equal loudness.

Subject Classification: [43]65.50, [43]65.22, [43]65.75.
On an invariance property of acoustic waveguides
Authors: Davis Sanford S.
Published: October 2005

The acoustic power transmitted by a variable-area duct section which carries a steady subsonic flow is investigated under the conditions of both upstream- and downstream-propagating incident plane waves. It is found that the ratio of the power transmitted by incident waves moving against the flow to the power transmitted by incident waves moving with the flow bears the simple relation (1−M2)/(1+M)2.

Subject Classification: [43]28.60; [43]20.45.
California sea lion underwater auditory detection and variation of reinforcement schedules
Authors: Schusterman Ronald J.
Published: October 2005

A sea lion (Zalophus californianus) was trained to report the presence of a pure tone under water in a yes–no psychophysical procedure. The payoff matrix was varied by altering the probability of fish reinforcement [P (SR)] contingent on two classes of response—hits and correct rejections (CR). The P (SR‖Hit) and the P (SR‖CR) were 1.00, 0.75, 0.50, and 0.25. In baseline, both P (SR‖Hit) and the P (SR‖CR) were = 1.00. In the asymmetrical payoff matrices P (SR) was held constant at unity for one response and varied over three values for the other response. Thus, seven different payoff matrices were used. The sea lion showed rapid acquisition of a stable response bias independent of its ability to detect the underwater auditory signal. These results demonstrate that varying reinforcement probability is functionally equivalent to varying amount of reinforcement in the control of response bias in underwater signal detection by sea lions [see R. J. Schusterman, B. Barrett, and P. Moore, J. Acoust. Soc. Am. 57, 1526–1532 (1975)].

Subject Classification: [43]80.50, [43]80.60.
Frequency-dependent influence of the sea bottom on the near-surface sound field in shallow water
Authors: Murphy E. L. , Wasiljeff A. , Jensen F. B.
Published: October 2005

The influence of the sea bottom on shallow-water sound propagation can be especially pronounced for the sound field near the boundaries. Comparison of the near-surface sound field with the mid-depth field, for example, can serve as a useful diagnostic tool for understanding the frequency-dependent influence of the sea bottom on sound propagation in shallow water. Broad-band shallow-water sound-propagation data analyzed in one-third octave bands are compared for a very shallow receiver (2 m) and a mid-depth receiver (50 m). The data are also compared with results from modal calculations. The interplay between the behavior of the modal depth functions and modal attenuations, as frequency is varied, provides a convenient model for interpreting the results.

Subject Classification: [43]30.20, [43]30.30.
Absorption of sound by sound
Authors: Westervelt Peter J.
Published: October 2005

Earlier studies [J. Acoust. Soc. Am. 29, 934 (1957)] of the mutual nonlinear interaction of two plane waves of sound with each other exhibited a singularity when the waves became collinear. The singularity is removed in this study, which leads to a method for calculating the pressure absorption coefficient α of a wave with wave vector k1 resulting from interaction with isotropic acoustic waves having the energy density spectrum u (k). Thus, α= (4ρ0c20)−1(1+1/2Λ)2π ℱk1 0 ku (k) dk+k1ℱ∞d1 2u (k) idk+k21ℱk11k−1u (k) dk], in which ρ0 and c0 represent the density and velocity of sound of the fluid which is assumed to be dispersionless. The constant 1/2Λ =ρ0c d0−1(dc/dρ)ρ0.

Subject Classification: [43]25.22, [43]25.35.
An investigation of speaker photograph identification
Authors: Lass Norman J. , Harvey Lisa A.
Published: October 2005

The purpose of this investigation was to determine whether listeners were capable of speaker photograph identification based on recorded speech samples. A standard prose passage was recorded by 30 speakers, 15 females and 15 males. A master tape of all recorded readings was played to a group of 30 subjects for speaker photograph identification purposes. The subjects were shown photographic slides of two persons on a screen and simultaneously heard a tape recording of a single speaker reading the standard prose passage. Their task was to determine to which of the two photographs the speaker’s voice belonged. All subjects participated in two experimental sessions. In one session they were shown full-view photographic slides and in another, portrait-view slides. The order of presentation of the two kinds of slides was randomized so that 15 subjects were shown full-view slides first and 15 subjects were shown portrait-view slides first. Subjects were also asked to indicate the confidence of their speaker photograph identifications on a seven-point rating scale, and to describe the criteria upon which they based their decisions. Results indicate that the subjects were capable of identifying the full-view photographs of female and male speakers with slightly better than chance guessing accuracy when presented with their recorded speech samples. Implications of these findings and suggestions for future research are discussed. Subject Classification: [43]70.30, [43]70.65.
Influence of anisotropic liners on the attenuation of sound in circular ducts
Authors: Sun John , Nayfeh Ali H.
Published: October 2005

An analysis is presented of the sound propagation and attenuation in a circular duct carrying a uniform mean flow and lined with an anisotropic porous material backed by cellular cavities. A combination of a fourth-order Runge–Kutta routine and a Newton–Raphson procedure is used to determine the effects of the liner properties, the flow Mach number, and the sound frequency on the attenuation of spinning and nonspinning modes. The results show that low-frequency noise is better attenuated by anisotropic liners. The optimum liner is the one whose axial resistivity increases with increasing frequency.

Subject Classification: [43]20.45, [43]20.35; [43]50.40.
Acoustic performance of a stretched membrane and porous blanket combination
Authors: Thomas W. A. , Hurst C. J.
Published: October 2005

The sound absorption performance of an acoustic absorber consisting of a stretched circular membrane placed a short distance in front of a fiberglass blanket was both measured and predicted. Both theoretical and experimental analyses were restricted to plane acoustic waves. Theoretical predictions indicated that the membrane–blanket combination would have a sound power absorption coefficient nearly equal to the sound power absorption coefficient of the blanket alone if the incident acoustic plane wave drove the membrane at one of its resonance frequencies. Theoretical analysis also predicted that the sound power absorption coefficient would approach zero when the membrane was driven at an antiresonance frequency by the incident acoustic plane wave. Experimental agreement with theoretical predictions was good for several membrane–blanket combinations. The results show that membrane–blanket combinations can be effective acoustic absorbers in frequency ranges which do not include the antiresonance frequencies of the membrane. The equations developed may be used to predict the acoustic performance of any membrane–blanket combination.

Subect Classification: [43]20.30, [43]20.60; [43]40.20.
Reflection loss of the refracted–surface-reflected acoustic path in the ocean
Authors: Junger M. J.
Published: October 2005

The surface reflection loss suffered by refracted-surface-reflected rays is formulated asymptotically for long-range transmission. Like the absorption loss, it is proportional to range and to frequency squared.

Subject Classification: [43]30.20, [43]30.25, [43]30.30.
Comments on ’’Vibration of generally orthotropic skew plates’’
Authors: Nair P. S. , Durvasula S.
Published: October 2005

The free vibration problem of unstressed and stressed generally orthotropic skew plates using an integral equation approach is considered by Srinivasan and Ramachandran [J. Acoust. Soc. Am. 57, 1113–1118 (1975)]. Some comments on the convergence aspects of their results are offered here. Also, certain features of the nodal patterns and frequency plots are discussed.

Subject Classification: [43]40.24.
Recording the electrocochleographic (ECochG) response in humans: A reply to A. C. Coats [J. Acoust. Soc. Am. 56, 708–711 (1974)]
Authors: Moore Ernest J.
Published: October 2005

Coats (1974) investigated the effects of different electrode contact-points in recording the electrocochleograhic (ECochG) response of humans. He recorded from a needle electrode positioned at various places within the ear canal, from a specially fabricated intra-auricular electrode, and from an earlobe clip. He concluded that the earlobe-clip electrode was unsatisfactory for ECochG recording. Evidence is presented contrary to his conclusion, as it is demonstrated that the earlobe-clip electrode in combination with a more distant electrode is a satisfactory method for obtaining the ECochG response.

Subject Classification: [43]65.80; [43]85.92.
On musical notations—again
Authors: Bowsher J. M.
Published: October 2005

In view of the difficulty of reaching agreement about a system of unambiguous musical notation not using the stave, a proposal based on the recognized importance of the concept of ’’middle C’’ is put forward.

Subject Classification: [43]75.23.
The effect of ultrasonic cavitation on protein antigenicity
Authors: Edwards J. H. , James C. J. , Coakley W. T. , Brown R. C.
Published: October 2005

The antigenicity and enzyme activity of dilute solutions of RNAse exposed to ultrasonic cavitation have been measured as a function of exposure time. The rate of decrease of antigenicity was one-eighth of the rate of enzyme activity loss. The implication of the results for the use of ultrasound in antigen preparation is discussed.

Subject Classification: [43]80.40.
On the rotational collison number for air at elevated temperatures
Authors: Bass H. E. , Sutherland L. C.
Published: October 2005

A detailed review of the experimental data for the rotational collision number Zrot for air, O2 and N2 has been made to finalize a temperature correction for the absorption due to rotational relaxation for incorporation in a draft standard on air absorption being prepared by the Sl−57 Committee on Propagation.

Subject Classification: [43]35.20, [43]35.35.
Transmission and reflection of Rayleigh waves by a high impedance obstacle of finite length
Authors: Yoneyama Tsukasa , Nishida Shigeo
Published: October 2005

A new method is presented for calculating the transmission and reflection coefficients of Rayleigh waves by a high impedance obstacle of finite length. The problem is formulated in terms of simultaneous integral equations which can be solved by a kind of iterative procedure. As a result, the transmission and reflection coefficients can be expressed by complex contour integrals along branch cuts associated with a function in the integrands. The transmission and reflection coefficients are computed numerically by assuming a fused-silica substrate and are compared with those obtained by using Jones’s method of approximation. It is inferred that the present approach, though it takes more computing time when compared to Jones’s method, can predict the transmission and reflection coefficients with reasonable accuracy even if the obstacle is small.

Subject Classification: [43]35.54; [43]20.15, [43]20.30.
Acute changes in animal inner ears due to simulated sonic booms
Authors: Reinis Stanislav
Published: October 2005

C57BL/6 inbred mice were subjected to simulated sonic booms of different rise time, intensity, and number of sonic booms. The most important pathological change was found to be bleeding in the basal turn of the scala tympani of the inner ear. Even a single boom having a rise time of 0.1 msec, peak overpressure of 3.3 psf, and duration of 120 msec was found to cause bleeding in at least one inner ear of each exposed mouse. Similar results occurred for a single ’’superboom’’ having a 10−psf peak overpressure but a longer rise time of 5 msec. The frequency of the appearance of blood clots in the scala tympani was found to increase with the number of booms administered. This cumulative effect was observed even when the booms were administered at the rate of one every 24 h. The traces of bleeding usually disappeared within a period of eight weeks. The extent of the bleeding in the scala tympani did not increase when mice were exposed to a rapid succession of simulated sonic booms (18 000 booms in one hour). However, three out of twenty mice suffered a rupture of the basilar membrane and destruction of the Corti organ in the basal turn of the cochlea.

Subject Classification: [43]65.20, [43]65.40; [43]50.70; [43]80.40.
Comparison of the reliability of an Auraldome headset and a standard headset in obtaining pure-tone audiometric threshold measures
Authors: Vogen C. S. , Copeland A. B.
Published: October 2005

An Auraldome headset and standard headset (TDH−39/MX−41/AR) were compared via threshold measures, probe tube microphony, and coupler measures. The same TDH−39 receiver was used in each headset. Test–retest threshold and probe tube measures with the Auraldome and standard headset were elicited from the right ears of 30 normal hearing adults at 10 audiometric frequencies (250–8000 Hz). Statistical and descriptive comparisons of headset performance were carried out. For threshold measures at each frequency, intersubject variances of the two headset were compared statistically, as were their intrasubject variances. Descriptive comparisons were also made of the probe tube and coupler data. The threshold data and physical data, considered together, permit comparison of the reliability of the two headsets, as well as allowing comparisons of their real-ear-to-coupler errors. Results demonstrated the suitability of the Auraldome headset for audiometric purposes with adults; however, omitting 8000 Hz from the testing protocol will improve the headset’s reliability. Also shown was the validity of the probe tube microphone methodology used in this study for transferring threshold standards from conventional to unconventional earphones.

Subject Classification: [43]85.76; [43]65.80, [43]65.50.
Frequency spectra of extensional vibration in Pb(Zr⋅Ti)O3 disks with Poisson’s ratio larger than 1/3
Authors: Ikegami Seiji , Nagata Takashi , Nakajima Yasuo
Published: October 2005

The frequency spectra of axially symmetric extensional vibration in piezoelectric Pb(Zr⋅Ti)O3 ceramic disk plates having Poisson’s ratio (σ) of 0.37 have been investigated theoretically and experimentally. The theoretical frequency spectra were calculated with approximation of elastically isotropic disk plates for r (diameter/thickness) of 1 to 30. It was found that the terrace-type spectra which appear in a frequency band between the cutoff frequency of the symmetric thickness-shear mode and the frequency minimum Ω* do not construct a constant frequency bandwidth, in contrast to the case of σ<1/3. Experimental spectra were observed with the Pb(Zr⋅Ti)O3 disk plates for r of 4.8 to 7.2. The experimental spectral agreed well with the theoretical ones, by fitting the cutoff frequency of the fundamental thickness-extensional mode of the elastically isotropic plate to that of the piezoelectric Pb(Zr⋅Ti)O3 ceramic plate. From the results of these analyses, it has been found that the Pb(Zr⋅Ti)O3 ceramic disk plates have resonant vibration responses at or near the cutoff frequency of the symmetric thickness-shear mode, although these vibrations cannot be induced piezoelectrically.

Subject Classification: [43]40.24; [43]85.52.
Influence of consonant environment on duration of vowels produced by normal-hearing, hearing-impaired, and deaf adult speakers
Authors: Whitehead Robert L. , Jones Kenneth O.
Published: October 2005

The results of the present study have revealed that in a normal-hearing and a hearing-impaired population, vowels are significantly longer in duration in voiced-consonant environment, when compared with a voiceless environment. Vowels were also significantly longer in duration in a fricative environment when compared to a plosive environment. For a deaf population, the same trends were evident although the differences were not significant.

Subject Classification: [43]70.40, [43]70.75, [43]70.70; [43]65.64.
Comment on ’’Diffraction by iterative ray-theory techniques’’ [J. Acoust. Soc. Am. 56, 1342–1346 (1974)]
Authors: Hudimac A. A.
Published: October 2005

The errors of a ray-theory propagation from a simple harmonic point source in an inhomogeneous medium were shown to be corrected by a volume distribution of point sources of density whose amplitude and phase were simply related to the ray field. The radiation from the distributed sources was obtained by iterative ray techniques involving a perturbation approach, an integral equation, and use of an artifical wave number. Errors in the integral equation approach are corrected using two different methods. Physical interpretation of the two methods are compared.

Subject Classification: [43]20.20; [43]20.30.
Development of a high-power transducer DUMILOAD
Authors: Auyer S. E. , Miller W. A.
Published: October 2005

DUMILOAD (Dummy Mechanical Impedance LOAD) devices have been used to test transducers for many years. In concept the DUMILOAD consists of another specialized piezoelectric transducer mechanically coupled to the transducer to be tested. By varying the electrical impedance placed across the DUMILOAD’s electrical terminals, varying mechanical loads can be presented to the transducer being tested. Drawbacks to this approach have included the need for a cumbersome mechanical coupling device and the limited operating frequency band of the DUMILOAD. This paper describes some of the consideration involved in designing and constructing a DUMILOAD capable of operating at a power level of 1000 W in the frequency band from 3000 to 4000 Hz. Details of a ’’quick connect/disconnect’’ mechanical coupling device are also described.

Subject Classification: [43]85.40;[43]30.85
Scattering of acoustic signals by inhomogeneities in a waveguide—a single-scatter treatment
Authors: Sutton G. R. , McCoy J. J.
Published: October 2005

The title problem is studied using a single-scatter theory. General expressions are obtained for the distribution of scattered acoustic intensity among the waveguide modes and for a measure of azimuthal beam pattern of the intensity in a specified waveguide mode. Detailed calculations are carried out for a specified waveguide and for specified statistics of a fluctuating sound speed, which, while not being representative of actual ocean conditions allow our drawing conclusions that are applicable to ocean acoustic experiments. The importance, previously noted by Beran and McCoy, of the highly anisotropic nature of the fluctuations caused by internal waves on the scattering process is demonstrated. Several conclusions are drawn of the effects that this anisotropy can be expected to play in the multiple-scatter region.

Subject Classification: [43]30.40, [43]30.50; [43]60.20.
General treatment of source motion on the total acoustic field with application to an isospeed channel
Authors: Jacyna G. M. , Jacobson M. J. , Clark J. G.
Published: October 2005

A treatment of the effects of arbitrary motion of a cw source and depth-dependent sound speed on the total acoustic field at a fixed receiving point is considered for an ocean with horizontal boundaries. Application of our general method is made to a constant sound-speed channel in which the range-to-depth ratio is large, when the source follows a short straight-line path with constant velocity. Total-field phase is investigated as a function of receiver time for various source trajectories and phase rate is examined in terms of an arbitrary, but fixed, acoustic frequency. It is shown that source motion may be accounted for by assuming the sound source to be stationary, and by replacing its frequency by approximate Doppler frequency. For long source trajectories, cumulative phase can be approximated as a hyperbolic function of time. The outputs of two uniform colinear arrays, together with power spectra there, are employed to illustrate one method for determing source speed, location, bearing, and frequency.

Subject Classification: [43]30.20; [43]20.20..
Observations of acoustic sidebands in cw tones received at long ranges
Authors: Shooter Jack A. , Mitchell Stephen K.
Published: October 2005

Theoretical predictions, as well as observations at relatively short ranges and steep grazing angles, show that a sound wave which is forward scattered from the ocean surface has its frequency components smeared by surface-wave motion [M. V. Brown and G. V. Frisk, J. Acoust. Soc. Am. 55, 744–749 (1974)]. The subject of this paper is the presence of observable sidebands in cw signals which are generated by a moving source received at ranges of up to 200 NM in the deep ocean. The sidebands are approximately 0.1 Hz from the source center frequency and are as strong as 20 dB below the level of the signal received at the source frequency.

Subject Classification: [43]30.20, [43]30.30, [43]30.40.
Instrument for microscopical observation of the biophysical effects of ultrasound
Authors: Miller Douglas L.
Published: October 2005

In this instrument, a quartz driver, thickness resonant at 1 MHz, and a thin cover were concentrically mounted on the stage of a microscope. Electroding was omitted over a central area to allow transmitted-light observation of the test space between them. We approximate the acoustic field generated in the cylindrical test volume by a standing-wave solution to the linearized wave equation. The boundary values were (i) zero pressure at the radial boundary and (ii) interferometrically determined values of the acoustic displacement at the driver and cover. The truncated-series solution was successfully used to explain the radiation-force-induced migration of small polystyrene spheres suspended in the water-filled test space. In addition, the determined pressure distribution substantially agreed with independent measurements obtained by interferometrically detecting (via the acousto-optical interaction) the pressure oscillations, averaged over height.

Subject Classification: [43]80.30; [43]35.75.
Elastodynamics: Author’s comments on the reviews of E
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I (Academic, New York, 1974 and 1976) [J. Acoust. Soc. Am. 58, 539–540 (1975); 60, 1236–1237 (1976)]
Authors: Eringen A. Cemal , Suhubi Erdoğan Ş.
Published: October 2005

The authors of the books in question comment on the reviews appearing in the Journal and indicate their disagreement with many of the points raised.

Subject Classification: [43]40.10.
Environmental effects on microphones of various constructions
Authors: Hruska Gale R. , Magrab Edward B. , Penzes William B.
Published: October 2005

The pressure sensitivities of two 1/2-in. electret, two 1-in. ceramic, and two back-vented 1-in. condenser microphones were measured for numerous combinations of temperature, percentage relative humidity, and frequency. The two condenser microphones were calibrated by the reciprocity technique at each combination of temperature, relative humidity, and frequency. The condenser microphones were then used as calibrated sources to determine the pressure sensitivities of the other microphones. Insert voltage techniques were used to eliminate the environmental effects on the electronics. It was found that the back-vented condenser microphones are insensitive to changes in relative humidity. At frequencies considerably below their resonance frequencies they exhibited only a very small change in sensitivity with temperature. At frequencies closer to the resonance frequency the temperature coefficient increases approximately fourfold. The temperature and humidity coefficient for the electret and ceramic microphones could not be determined due to the instability in their sensitivities which produced changes that were larger than those induced by the temperature and humidities.
Directional accuracy of small ring arrays
Authors: Maksym J. N.
Published: October 2005

Estimation of the bearing of a farfield signal source with a small-diameter circular array of hydrophones is studied in this paper. It is shown that for isotropic farfield noise the Cramér–Rao bound can be simply evaluated via a spatial harmonic representation of the array response. Use of the derived expression for practical bearing estimators employing superdirectivity is justified by showing the equivalence between the maximum-likelihood estimate and one obtained by the formation of superdirective beams. An expression for the average bias resulting from anisotropy of the ambient-noise field is also derived using a spatial harmonic representation.
Forcid vibrations of simply supported orthorpic sandwich plates
Authors: Bhat B. R. , Sinha P. K.
Published: October 2005

Force transmissibility, driving-point impedance, and transfer impedance of a simply supported rectangular orthotropic sandwich plate are investigated. The plate is driven by a sinusoidally varying point force either at the plate center or at any arbitrary location. The variation of force transmissibility and impedance with frequency, and the manner in which this is influenced by the various sandwich-plate parameters are studied and presented graphically.
Geometric factors affecting hydrophone performance
Authors: Winnicki R. T. , Auyer S. E.
Published: October 2005

The application of the finite-element method of analysis to investigate the geometric and material factors which affect the open-circuit voltage sensitivity of a class of underwater acoustic hydrophones is discussed. This class of hydrophones consists of an air-filled, right-circular, piezoelectric ceramic cylinder with flat nonpiezoelectric circular disk end caps. The study examines the factors which constrain the motion of the cylinder in a real hydrophone and cause the open-circuit voltage sensitivity to be less than the value of an ideal hydrophone predicted by the equations developed by R. A. Langevin [J. Acoust. Soc. Am. 26, 421–427 (1953)]. Curves are presented to allow an estimate to be predicted of the reduction in the open-circuit voltage sensitivity which a particular design will produce, and a comparison is made between these predictions and empirical data measured on various hydrophone configurations.
Noise generated by axisymmetric turbulent boundary-layer flow
Authors: Lauchle Gerald C.
Published: October 2005

The noise generated by hydrodynamic flow over an axisymmetric body with a blunt noise is described quantitatively. Flush-mounted piezoceramic hydrophones were used to measure that part of the turbulent boundary-layer pressure fluctuations that propagates as true sound. Power spectra of the sound pressure were measured in a 3–50-kHz frequency range over a wide range of Reynolds numbers (U∞D/ν?3.03×106, where D is the diameter of the body) for the model operating in the Garfield Thomas water tunnel. The use of flush-mounted hot-film probes to locate turbulence transition is also described. The power spectra of the noise measured in the laminar flow regions correspond closely to those measured in the transition and fully developed turbulent regions of the flow. The exceptions were those spectra measured on the flat part of the nose, but correction for diffraction-loss effects suggests that the noise measured there is due to the noise generated by the turbulent part of the flow. Nondimensionalization of the noise spectra measured at various arc lengths with theoretical expressions for the noise expected, that include a critical boundary-layer thickness at the beginning of turbulence, show a general collapse of data to within 6 dB. When applicable, comparisons of the radiated noise measured on buoyant bodies are made and agreement was found to be excellent.
Comparison of FFT and Prony algorithms for bearing estimation of narrow-band signals in a realistic ocean environment
Authors: Bucker Homer P.
Published: October 2005

Samples of the quadrature field {Fj} collected on a uniform linear array can be quickly analyzed to determine the bearings of targets by use of the FFT or Prony algorithm. These methods are compared for many realizations of a realistic ocean acoustic signal plus background plus noise field. The familiar Monte Carlo method is used to quantify the algorithm performance. It is shown that bearing accuracy can be improved by forming the cross-sensor field {Gl} where Gl=〈FjFj*+l〉. Theoretical and computational analysis indicate that time averaging of 〈FjFj*+l〉 not only reduces the effects of noise, but also reduces interactions of waves in the signal and background fields resulting in better array performance.
Adjointness properties for differential systems with eigenvalue-dependent boundary conditions, with application to flow-duct acoustics
Authors: Kraft Robert E. , Wells William R.
Published: October 2005

When the boundary conditions at the two endpoints of a second-order differential system depend explicitly upon the eigenvalues such that the system becomes non-self-adjoint, a generalized condition of orthogonality which includes endpoint terms can be developed. The generalized orthogonality condition is used to determine modal coefficients for the expansion of arbitrary functions in series of eigenfunctions. The method is applied to the particular case of acoustic wave propagation in a rectangular duct with a uniform mean-flow profile and walls with finite acoustic impedance. The ability of the eigenfunction expansion to converge to a plane-wave acoustic pressure profile is demonstrated under a variety of flow, frequency, and wall-impedance conditions.
Interference rejection by amplitude shading of sonar transducer arrays
Authors: Wang H. S. C.
Published: October 2005

It is demonstrated that strong coherent interference incident from arbitrary directions can be effectively rejected by amplitude shading or real weighting of channel signals. For a given spatial distribution of interference field, the total interference power received by a transducer array is formulated and superimposed on the power received from an isotropic noise field. The total noise plus interference power is then minimized with respect to the shading coefficients and subject to the constraint that the mainbeam peak be maintained at a fixed level. As an illustrative example, we have calculated the optimum amplitude shading coefficients for a linear array with logarithmically spaced transducer elements to reject an interference field uniformly distributed over a 15°×36° solid angle with an intensity up to 70 dB above the noise field. In each case, the directivity pattern of the array adjusts itself by bunching several null points in the direction of interference incidence to achieve a nearly complete rejection. The merit of a narrow-band processor based on the principle of optimum amplitude shading is then examined by comparing its performance with those of a conventional processor and an optimum processor with both amplitude and phase adaptation. The optimum amplitude shading processor is clearly superior to the ocnventional processor under strong interference, but much simpler to implement than the optimum processor with amplitude and phase adjustment. Furthermore, the very little additional SNR0 due to complex weighting probably cannot be achieved in practice because of the extreme super-gain condition which often results.
Power flow between strongly coupled oscillators
Authors: Gulizia Charles , Price A. John
Published: October 2005

The theory describing power flow between two sets of linearly coupled oscillators is re-examined for the case of arbitrary coupling strength. For simplicity, gyroscopic coupling is assumed and the equations of motion for two linearly coupled oscillators are solved using a Fourier-transform technique which is found to be useful to increase the ease and elegance of the derivation, as well as to retain an explicit frequency dependence in the solution. Some general assumptions are made on the shape of the Fourier transforms of the mechanical impedances, input forces, and the form of statistical independence. It is found that, as expected, the modal coupling coefficients are functionally dependent upon the strength of the coupling elements. As a limiting case, the result of [Lyon and Maidanik, J. Acoust. Soc. Am. 35, 623–639 (1962)] can be obtained by frequency averaging the coupling coefficient derived in the present analysis. However, it is found tha the radiation resistance can be obtained from the same equation as give by Lyon and Maidanik for weak coupling. Th results of an experiment designed to show the effects of strong coupling are described. The results are in fair agreement with the theoretical predictions from the first part of this paper.
Impedance models for grass-covered ground
Authors: Donato R. J.
Published: October 2005

Three different models are described in an attempt to account for the frequency dependence of measured impedances of grass-covered ground. These are (a) a homogeneous ground of constant porosity, (b) a finite layer, also of constant porosity, overlying an infinite impedance, and (c) porosity decreasing with depth. The latter structure provides the best fit to the experimental data.
Alternating electrical-resistance changes in the guinea-pig cochlea caused by acoustic stimuli
Authors: Geisler C. D. , Mountain D. C. , Hubbard A. E. , Adrian H. O. , Ravindran A.
Published: October 2005

A new method for measuring electrical-impedance changes that are elicited by tonal stimuli in the cochlea of the anesthetized guinea pig has been developed. Constant-amplitude currents of low-frequency sinusoidal waveform are delivered to scala media simultaneously with tonal stimuli. In the signal recorded from scala media, energy is detected at frequencies equal to the sum and difference of the applied frequencies. This energy is interpreted as due to changes ΔR in the resistance of the scala media that are synchronized with the acoustic waveform. The maximum magnitude of the change varies from about 0.2% in turn I to about 1% in turn III. During normal conditions, striking parallels exist between the behavior of ΔR and CM as both frequency and intensity are varied. However, under asphyxic conditions, the observed change in ΔR is usually much less than that in CM. The results are shown to be qualitatively, though not quantitatively, consistent with a two-dimensional, variable-resistance model of the cochlea.
Three-dimensional computer simulaton of reverberation in an enclosure
Authors: Wayman James L. , Vanyo James P.
Published: October 2005

A computer simulation method, based on the ray theory of acoustics, has been developed for predicting reverberation decay rates in an architectural enclosure. Comparison of results to solutions of the Eyring equation and to a limited amount of experimental data are very favorable. The method can be extended to complex structures and provides useful results with limited effort.