bluuebunny/crossref_metadata_2025 huggingface dataset:
Amplitude-adaptive beamformer for planar arrays
Authors: Wang H. S. C.
Published: October 2005

An amplitude-adaptive beamformer configured for a class of planar arrays with quadrantal symmetry is conceived and described. The adaptive algorithm is developed based on the principle that directional interferences and noise can be rejected or minimized by adjusting the amplitude shading of the array elements with their phase shifts fixed [H. S. C. Wang, J. Acoust. Soc. Am. 61, 1251 (1977); J. Acoust. Soc. Am. Suppl. 1 62, S51 (1977)]. The algorithm utilizes an estimate of the covariance matrix of the interference and noise field from properly sampled and delayed “quad signals” of the array, thus reducing the number of independent adaptive channels by a factor of four. It can be shown that the algorithm converges to the optimum shading solution previously reported by the author. The performance of such an adaptive beamformer was demonstrated by simulation on a digital computer with a two-tone interference incident on a side lobe of a 52-element planar array. In a typical example, interference power at the beamformer output was reduced by 40.9 dB after 20 iterations.
Session II. Noise VII: Noise Measurements on Power Plant Fans in the Field—A Special Workshop
Authors: Hoover Robert M.
Published: October 2005

The focus of this panel session and open discussion will be how to obtain meaningful data on a variety of field installations of large power plant fans. From this discussion, it is planned that the speakers will develop guidelines for taking noise measurements in the field so that data from a variety of installations can be compared. An understanding of this data can lead to better methods than are presently available for predicting both in-plant and property line fan noise levels. To initiate the discussion, panelists have been invited to briefly discuss several major considerations required for obtaining meaningful field measurements. They will address questions related to the measurement of noise radiated by fan casings and duct breeching as well as that radiated from intake or discharge duct openings, measurement locations, instrumentation, and measurement procedures. Also, they will discuss the type of information to be included in any report on fan noise, including the fan characteristics (both design and operating data), and how to coordinate with the power company to obtain the most useful data on both the fan and the related power plant operations. Interested parties are invited to participate in the discussion and should come prepared to discuss: What to measure and where, instrumentation for measurements, fan and fan system characteristics, and relevant power plant operations.
Design of porous sound-absorbing materials
Authors: Brown Steven M.
Published: October 2005

The Zwikker-Kosten model of porous sound-absorbing materials [C. Zwikker and C. W. Kosten, Sound Absorbing Materials (Elsevier, New York, 1949)] is examined as a tool for designing and predicting the behavior of such materials. Experimental data are compared with theoretical predictions. Conclusions as drawn on the applicability of the model to developing or modifying architecturally significant sound-absorbing materials.
Measurement of normal incidence airborne sound transmission loss for open-plan office panels
Authors: Webster M. P.
Published: October 2005

A new laboratory test procedure is developed that evaluates the normal incidence sound transmission loss characteristics of a partial height panel. A comprehensive comparison of test data and the resulting single number ratings are made between the proposed and the existing barrier/sound transmission loss test procedures. Experimental attenuation measurements for various open-plan office configurations were in close agreement with calculated theoretical predictions using the geometrical theory of diffraction and normal incidence sound transmission loss test data. Measurements were conducted in a semi-anechoic room using a one-third octave band real time analyzer and pink noise as the test signal. The new test procedure provides one-third octave band data for complete acoustical analysis and a single number rating, called Weighted Articulation Index Average, for partial height panel comparisons.
Active acoustic absorbers for low-frequency hum
Authors: Angevine O. L. , Gupta Prem K. , Rushden F. A.
Published: October 2005

Previous attempts to cancel the 120-Hz hum of large power transformers by active means have relied only upon Young's principle [e.g., W. B. Conover, Noise Control 2, 78–82 (1956)]. M. Jessel established that Young's principle of interference can be combined with Huygens' principle of virtual sources [Brevet Français 1, 494–967 (1966)]. This new theory suggested a technique by which the sound field may be cancelled completely outside of a Huygens' surface surrounding a primary source, by employing a number of secondary sources at the Huygens' surface, which act as active sound absorbers. The theory has been realized experimentally for sound in a duct [M. Jessel and G. Mangiante, J. Sound Vib. 23, 383–390 (1972)] and in three dimensions for a small simple source [G. Mangiante, D.E.S. Fac. Sciences, Marseilles (1968)]. This technique has been applied by the authors to a small acoustic model of a large distribution substation transformer in a free-field over a reflecting plane. Six-ten dB attenuation of the fundamental frequency has been achieved everywhere in the farfield using only a limited number of secondary sources. Cancellation of two hum components simultaneously has been achieved also. It also has been found that attenuation over a limited horizontal angle does not increase the radiation outside this angle significantly.
The Navy's Air Installation Compatible Use Zone Program: A status report
Authors: Stewart Allen
Published: October 2005

The importance of unobstructed and controlled airspace in proximity to airports was one of the prime factors that influenced the siting of military air installation and the retention and expansion of these facilities. Over the past few years, however, rapid urbanization has adversely effected both military and civilian airports. For example, communities are becoming more critical of aircraft noise and increasing pressure is being applied by local government and of all the military services, the navy has faced the most intense pressure because the majority of its air stations are located in costal areas which have experienced growth rates far exceeding the natural metropolitan average. The Department of Defense responded to this problem by initiation of the Air Installation Compatible Use Zones (AICUZ) Program to protect the public's safety, health, and welfare while forestalling degradation of the operational capability of military air installations. The main intent of AICUZ program is to insure that development of surrounding land will be compatible with the noise levels and accident potential associated with airfield operations. The Navy endeavors to achieve this compatibility through an appropriate mix and locally adopted land use controls such as zoning, easements, and sound attenuation measures.
Shadowing by finite noise barriers
Authors: Medwin H.
Published: October 2005

A technique is described for calculating the acoustical shadowing due to finite barriers. The method is an extension of the Biot-Tolstoy rigorous closed form impulse solution for diffraction by an infinite rigid wedge [J. Acoust. Soc. Am. 29, 381–391 (1957)]. By discrete Fourier transformation, spectral predictions for infinite plates or wedges are obtained which are about 3 dB closer to experimental results than previous theoretical estimates. Furthermore, the limitations of the Kirchhoff assumption are avoided and accurate predictions can be made for complicated finite barriers as well. Comparisons of theory and experiment are shown. [Work supported by ONR.]
Acoustic properties of the external auditory canal in chinchilla, guinea pig, cat, and man
Authors: Teas D. C. , Hill R. E. , Dolan D. F. , Walton J. P. , Patterson J. H. , Burdick C. K.
Published: October 2005

The acoustic pressures produced by a band of noise were measured at the entrance to the auditory canal and near the tympanum. The stimuli was produced by a TDH-39 earphone activated by a noise band tailored to produce an approximately flat spectrum between 0.1 and about 4 kHz at the entrance to the ear canal. A computer program calculated the output power spectra, the signal/noise, the cross-power spectrum, the transfer function, the coherence function, and the phase between the input and output power spectra. The transfer function in each animal shows an upper frequency peak, the location of which varies with the apparent volume of the canal, being highest for the guinea pig and lowest for man. The magnitude of the resonance is largest for the cat and smallest for the guinea pig. [Supported in part by DAMD 17-78C-8067 and NSF-77-16907.]
Spectrum of the CM produced by high-intensity, low-frequency noise bands in the chinchilla
Authors: Teas D. C. , Hill R. E. , Dolan D. F. , Walton J. P. , Patterson J. H. , Burdick C. K.
Published: October 2005

High-intensity, low-frequency octave band noise in the free field has been reported to produce permanent threshold shift at 2 kHz in chinchillas [Burdick, Patterson, Mozo, and Camp, J. Acoust. Soc. Am. 64, 458 (1978)]. We have delivered 100- and 250-Hz low-pass noise to the chinchilla with intact pinna but open bulla and have measured the spectrum of the CM recorded with electrodes in turn I and turn II. SPL's were measured at the pinna. The output of the microphone was led to channel 1 of an A/D converter. The CM was led to channel 2. The inputs to the A/D's were adjusted to the same rms level to minimize digital noise. A computer program calculated FFT's and produced several calculations from them (see previous abstract). At SPL's below 100 dB, the output spectrum (CM) is similar to the input spectrum (microphone). Above 100 dB the output spectrum contains frequencies above the passband of the input spectrum. The coherence function indicates that the high-frequency output is not present in the input power spectrum. [Supported in part by DAMD17-78C-8067 and NSF 77-16907.]
Natural frequencies of a finite-element model of the cat eardrum
Authors: Robert W. , Funnell J.
Published: October 2005

The vibrations of the cat eardrum are being modelled using the finite-element method. The three-dimensional, linear, low-frequency model previously reported [W. R. J. Funnell, J. Acoust. Soc. Am. 63, 1461–1467 (1978)] has been further developed by the addition of inertial terms. The first several natural frequencies have been calculated as functions of various parameters of the model, including drum curvature and ossicular load. The ossicular moment of inertia strongly affects the lowest natural frequency, but has little effect on the higher ones. The three-dimensional curvature of the eardrum affects the higher modes most strongly. The importance of quantitative eardrum shape measurements [W. R. J. Funnell, J. Acoust. Soc. Am. 65, S9 (1979)] is discussed. [Work supported by the Medical Research Council of Canada.]
COCB stimulation alters cochlear mechanics as reflected in earcanal pressure measurements
Authors: Mountain D. C.
Published: October 2005

The distortion product (f2 − f1) was measured in the sound pressure near the eardrum. Stimulation of the cochlear efferents (COCB) decreased the level of the distortion product. The percent reduction was largest at lower primary intensities. A decrease of the endocochlear potential (EP) caused a similar decrease in the distortion product. A decrease in EP would presumably depolarize the apical hair cell membrane and would hyperpolarize the basal and lateral portions of the membrane. The efferent stimulation would hyperpolarize the entire membrane. A comparison of the two types of experimental results suggests that the potential across the lateral or basal portion of the hair cell membrane plays an important role in influencing the linearity of cochlear mechanics.
Cochlear potentials in deafness and jerker mice
Authors: Bock Gregory R. , Steel Karen
Published: October 2005

Anatomical studies using light microscopy have shown that mice affected by the deafness or jerker genes develop cochlear hair cells which at first appear to be normal. The hair cells then begin to degenerate, and by about three months of age most of the organ of Corti has degenerated. The object of the present study was to determine whether the cochleas of affected animals are functionally normal during the period when they appear structurally normal. Mice from the two strains aged between 12 and 50 days were anaesthetized and audiograms were determined by measuring thresholds for detecting the compound action potential recorded at the round window. No action potentials or cochlear microphonics could be recorded from affected animals at any age but littermates unaffected by the respective genes had normal thresholds. These results indicate that the apparent structural integrity of the cochleas of young deafness and jerker mice is not accompanied by normal function. Mice affected by these genes appear to be completely deaf at all stages of cochlear development.
Signal detection by low-frequency cells of the ventral cochlear nucleus
Authors: Langford Ted L. , Gidda Jaswant S.
Published: October 2005

The responses of low-frequency, “primary-like” cells of the ventral cochlear nucleus to several signal-masker combinations were measured. Signals were 100-ms, best-frequency tones. Maskers were either wide-band (0–10 kHz) or narrow-band (0.2 × cell's best frequency) “multiplied” noises presented either continuously or gated with the signal. Masker levels were held constant while signal levels were varied in 2-dB steps over a signal-to-noise ratio (S/N) range of +5 to +23. Little correlation was found between SIN and discharge rate for any condition. A nearly linear relationship between S/N and the degree of phase locking, as measured by the synchronization coefficient, existed, however, for all conditions. For the population of units sampled, it appears that information regarding the presence of a partially masked, low-frequency signal is carried in the form of phase-locked responses. [Work supported by NIH.]
Can intensity discrimination be uniquely related to available data
Authors: Colburn H. S.
Published: October 2005

Predictions of intensity discrimination models depend critically on assumptions about the following aspects of auditory-nerve activity: The nature of the randomness; the importance of the time structure relative to the mean rate of firing (count); the saturation of the rate-intensity function; the distribution of thresholds of fibers with a common characteristic frequency (CF): the distribution of CF's over fibers; the shapes of tuning curves, especially the tails; the dependence of the rate-intensity functions both on the CF relative to the stimulus frequency and on other characteristics of the fiber (e.g., spontaneous rate); and the nonlinear interactions that occur with several stimulus components (as in partial masking experiments). In addition, predictions are sensitive to the way information from different fibers is assumed to be combined centrally. Unfortunately, there exist different sets of assumptions that both correctly predict the psychophysical data and are roughly consistent with available physiological data. In spite of this theoretical latitude, many current models make assumptions that contradict available physiological data. [Work supported by NIH.]
Tuning curves with noise and sinusoidal maskers
Authors: Weber Daniel L. , Patterson Roy D.
Published: October 2005

Tuning curves were generated using narrow-band (50 Hz wide) noise and sinusoidal maskers for three signal conditions for both simultaneous and forward masking. Tuning curves for a brief (5-ms) 1-kHz sinusoidal signal are compared to those for a longer (35-ms) signal of equal power (38.5 dB SPL) or equal energy (power equals 30 dB SPL). For all three signal conditions, the comparison of sinusoidal and noise tuning curves shows the same relation. In simultaneous masking, noise is a more effective masker near the signal frequency but in the low frequency tail the tuning curves cross and the sinusoid becomes the more effective masker. This reversal is clearly due to the interaction of masker and signal since the difference between sinusoidal and noise maskers disappears in forward masking. Tuning curves in forward masking show greater tuning than those in simultaneous masking with one exception. For the brief signal, there is no difference between the simultaneous and forward masking curves for the noise masker.
Frequency selectivity as a function of sound pressure level
Authors: Wightman Frederic , Raz Israel
Published: October 2005

Many hearing-impaired listeners appear to have poor auditory frequency selectivity. However, the data are confounded by the fact that these listeners are usually tested at high SPLs. There is evidence that even in normal listeners frequency selectivity is diminished at high SPLs, though there is some question about the size of this level effect. In two different experiments directed at this issue, we found the decrease in normal selectivity at high SPLs to be small and highly subject dependent. In the first, psychophysical tuning curves were obtained from six listeners at probe levels 40 dB apart. The probe was set at 10 dB SL; the low-level condition was run in quiet, and the high-level condition in a background of intense wide-band noise. The average tuning curve from the high-level condition was a little wider, but one listener actually produced a narrower curve in this condition. In the second experiment we measured the threshold of a tone masked by noise with a cosinusoidal power spectrum. Threshold was first measured with the tonal probe at a spectral peak, and then with the probe in a valley. The difference between the two thresholds, our measure of frequency selectivity, was about 2 dB less at high probe levels than at low probe levels, suggesting only a slight reduction in frequency selectivity at high levels. These results support our view that the deficit in selectivity exhibited by hearing-impaired listeners is not an artifact due to stimulus level. [Work supported by NIH Grant No. NS12045.]
Psychophysical tuning curves in the parskeet: A comparison between simultaneous and forward masking procedures
Authors: Kuhn Angelika , Saunders James C.
Published: October 2005

In experiments with human listeners the shape of psychophysical tuning curves (PTC) has been shown to vary with the masking procedure. The present experiment was designed to see if PTC shape was also dependent on masking procedure in the parakeet. Four animals were trained to respond in the presence of tone stimuli and PTCs were measured for probe frequencies of 1.6, 2.5, or 3.5 kHz using either a simultaneous or forward masking paradigm. The sharpness of the tuning curves varied drastically with procedure and the forward masking curves had Q10dB values that were nearly double those obtained from the simultaneous masking procedure. Although there were differences in the sharpness of tuning, the PTCs from both methods remained generally symmetrical on the high- and low-frequency side of the probe signal. The results are considered with regard to two-tone suppression and pitch discrimination cues. [Work supported by Heinrich-Hertz Foundation, West Germany.]
Backward masking of human brainstem responses
Authors: Stanny R. R. , Peeples V. E. , Elfner L. F.
Published: October 2005

Backward masking of wave V responses was investigated as a function of probe-to-masker intensity ratio (Ip/Im) and interstimulus silent interval (Δt). Stimuli were 0.5-ms segments of broadband noise with N0 from 20 to 55 dB SPL. Maskers were always 55 dB SPL (about 45 dB SL). Values of Δt ranged from 0.5 to 8.0 ms. Combinations of (Ip/Im) and Δt which produced probe and masker responses of identical latency profoundly reduced probe responses. Here, the response to probe-plus-masker was negligibly larger than that to masker alone and reliably (i.e., with p > 0.995) smaller than that to a stimulus 3 dB above Im. When probe and masker responses partially overlapped, the probe response peaked first, and Ip/Im was less than about -20 dB, the probe response was masked in the region of overlap. When Ip/Im exceeded about -20 dB, partial or near overlap produced strong forward masking of the nominal masker's response. Backward masking was not observed when probe and masker responses did not overlap, nor when probe and masker were presented to opposite ears.
Computer-averaged input-output curves and visual detection levels in methylmercury-poisoned guinea pigs
Authors: Wilpizeski C.
Published: October 2005

The present electrophysiological study was done to confirm an expected low-tone dysfunction in guinea pigs poisoned with cumulated doses of methylmercury. Forty young-adult Hartley strain guinea pigs were fitted stereotaxically with permanent recording electrodes having tips in the auditory tubercle and on the dural surface of the cerebrum. Twenty animals were injected subcutaneously with cumulated doses (2 mg/kg/day) of methylmercury chloride solution five times per week for periods ranging from 10 to 38 days. Twenty control subjects were injected with comparable volumes of sterile water. Click- and pure-tone-evoked responses were recorded during the waking state using a summing computer. Neither input-output functions nor visual detection levels for tones from 0.125 through 16 kHz provided any evidence for low-tone dysfunction in methylmercury-treated subjects. Supranormal evoked response amplitudes were seen at 8 and 16 kHz. Contrary to earlier conclusions based only on morphological data, the guinea pig as a species appears to be an inappropriate model for methylmercury-induced deafness reported in human victims.
Assessment of hearing sensitivity in normal newborns and adults using the slow negative scalp response at 10 ms (SN10)
Authors: Hawes M. D. , Greenberg H. J.
Published: October 2005

The recently discovered slow negative brain stem response at 10 ms (SN10) was investigated as a tool for assessment of hearing sensitivity in 20 normal newborns and adults. Tone pips of 500, 1000, and 2000 Hz and a click were presented at 60, 40, and 20 dB re normal hearing level. The SN10 response varied systematically as a function of frequency and intensity. The SN10 response was not observable for all stimuli; however, percentages of detection improved as frequency and intensity increased. Newborns demonstrated significantly longer latencies than adults for all stimuli. Overall results suggested that SN10 is a reliable indicator of hearing sensitivity for frequencies of 1000 Hz and higher.
Hearing evaluation in families with familial hypercholesterolemia
Authors: Zavoral James H. , Johnson David W. , Shrewsbury Donald W.
Published: October 2005

Hyperlipidemia has been implicated as a cause of sensorineural hearing loss. Forty-five subjects (25 male, 20 female), age 6 to 57, from families with familial hypercholestcrolemia were prospectively evaluated with pure-tone audiometrics (from 0.25 to 8 kHz) and serum lipoprotein quantification. Twenty had no lipid abnormality (N); 25 had familial hypercholesterolemia (FHC). All had clinically normal hearing and tympanometry. In 13 FHC and 11 N under 18, hearing at 6 and 8 kHz was reduced compared to age/sex adjusted values (NL) (p < 0.001). FHC compared to N were not significantly different. In 12 FHC and nine N over 18, there was reduced hearing compared to NL at selected frequencies. FHC vs N revealed reduced hearing in higher frequencies for males (3–8 kHz) (p < 0.01) and in lower frequencies for females (0.25–1 kHz) (p < 0.01). FHC and N from FHC families compared to NL had decreased hearing at selected frequencies at all ages. The difference between FHC and N was more pronounced in subjects over 18.
Growth functions of the acoustic reflex recorded with a 660-Hz probe
Authors: Thompson D. J. , Gary H. E. , Howington L.
Published: October 2005

The relationship between chronological age and acoustic reflex growth was examined in 30 female adults in the 20 to 79 years age range. Acoustic reflex activity was recorded contralaterally in acoustic conductance and acoustic susceptance (mmhos). Growth functions were generated with ascending series of stimuli presented in 1-dB steps which began below the reflex threshold and were increased to 120 dB SPL. Four activating stimuli were used, three tones—500, 1000, and 2000 Hz—and a (high-pass) filtered noise. Static acoustic emittance was computed and reflex thresholds were obtained. Growth expressed in conductance was commonly a decreasing monotonic function. Patterns of susceptance growth, which were more complex than conductance and contained diphasic reflex responses, were grouped into categories. Older subjects tended to produce a reduced rate of growth or a smaller magnitude of reflex response, in agreement with data reported for lower probe tones [D. J. Thompson, J. A. Sills, K. M. Recke, and D. M. Bui, “Acoustic reflex growth in the aging adult,” J. Speech Hear, Res. (in press)]. Growth data were also converted to acoustic resistance and acoustic reactante.
Use of an alternating magnetic field device to track midsagittal plane movements of multiple points inside the vocal tract
Authors: Perkell J. S. , Oka D.
Published: October 2005

A three-channel magnetic field ranging device has been constructed incorporating previously-used principles [Hixon, J. Acoust. Soc. Am. 49, 603–606, (1971); van der Giet, J. Acoust. Soc. Am. 61, 1072–1076, (1977)]. Two large transmitting coils, each excited by a sinusoidal signal at a different frequency, are mounted on a helmet, above the forehead and below the occiput. Extremely small transducer-receivers consist of inductors mounted on a base with lead wires attached. The transducers are attached to the structures of interest and leads are brought out of the corner of the mouth. The magnetically induced signal in each transducer is demodulated to produce voltages which are related to distances between transmitters and transducer, allowing for spatial localization by triangulation. In spite of technical problems which remain to be resolved, the potential usefulness of such a device is indicated by preliminary results of a repetition experiment: The positioning of points on the tongue surface appears more variable in the direction parallel to the vocal tract midline at the place of constriction for point vowels than in the acoustically more critical direction, perpendicular to the midline. [Research supported by NIH Grant No. NS 04332.]
Glottal impedance of a two-mass model of the vocal cords
Authors: Carré R. , Guérin B.
Published: October 2005

Simulation, in the time domain, of a complete source-vocal tract model including the frequency-dependent losses is quite impossible. But, in order to study the volume flow at the level of the glottis in the best conditions, we can use a two-mass model loaded by a circuit representing the impedance of the vocal tract. The spectrum of the volume flow has been calculated when the model is loaded by the representative impedance of the vocal tract and when court circuiting. The mean value of the glottal impedance has been determined from comparisons between both spectrums. This value has been measured for different frequencies corresponding to several vowel formants. Formant frequency variations due to the glottal impedance and synchronization effects (pointed out by amplitude variations around formant frequency} can be observed on the source spectrums. Some of these results are in agreement with the real data. Some others have to be verified. In conclusion, and with other results elsewhere reported, it seems that a two-mass model of the vocal cords is, until now, a good approximation of the real behavior of the glottal source.
Very low-frequency (VLF) wind-generated noise produced by turbulent pressure fluctuations in the atmosphere near the ocean surface
Authors: Wilson James H.
Published: October 2005

Measurements of ambient noise for very low frequencies (VLF) from 5 to 50 Hz indicate that wind-generated noise is a significant source of the total ambient noise field during high-wind/sea-state conditions. Determining dominant physical mechanism(s) for transfer of energy from the wind field into the underwater acoustic field is very important in modeling the wind-generated noise field at very low frequencies. Frequency dependence, wind speed dependence, directivity characteristics, and dependence on oceanographic parameters of the wind-generated noise source can be established only after the physical mechanism is understood. The objective of this paper is to extend the development of the theory of turbulent pressure fluctuations initiated by lsakovich and Kur'yanov. The wave height spectra of Mitsuyasu and Honda is incorporated into the theory, since this is the accepted wave height spectra in the VLF acoustic region. (These wave height data were not available to lsakovich and Kur'yanov at the time of publication of their original theory.) The wind speed and frequency dependence of the resulting source spectrum level agrees well with data measured in the north-eastern Pacific Ocean under low distant and local shipping noise conditions. [Work supported by NORDA Code 600.]
Computer model predictions of ocean basin reverberation for large explosions in the Atlantic and Pacific Oceans
Authors: Goertner Jean A.
Published: October 2005

Ocean basin reverberation results from interaction of the pressure wave from a large underwater explosion with the boundaries of the basin and of the seamounts and islands within it. Its net effect is to raise the ambient noise level at low frequencies for periods of from 30 min to 3 or 4 h. A computer model for predicting the reverberant field [J. A. Goertner and I. M. Blatstein, J. Acoust. Soc. Am. Suppl. 1 64, S45 (1978)] has proven itself repeatedly for varying conditions in the North Atlantic. As an important test of its validity, we have applied the model for three high-explosive shots, 0.6 to 1 kiloton in yield, one in the Atlantic and two in the Pacific, a basin with much greater area and myriad seamounts and islands. The remarkably good agreement between model results and data indicates that we can make reliable predictions not only for the Atlantic but for the much more complex Pacific as well. [Work supported by DNA.]
Dichotic and monotic interactions between VC's and CV's: Masking or articulatory constraints
Authors: May J. G. , Porter R. J. , Miller C. J.
Published: October 2005

Several reports by Haskins Laboratories' scientists [reviewed by Dorman, M. F., Raphael, L. J., and Liberman, H. M. (1979). Haskins Laboratories SRSR, SR-58, 105] suggest articulatory possibilities constrain the perception of VC1C2V sequences in which the (silent) closure interval varies in duration: for example, a VC1C2V sequence is perceived as a VC2V at short closure durations. It is argued that this phenomenon occurs because articulation-based perceptual decoding is constrained as is articulation: i.e., C1 cannot occur so soon before C2. However, the presentation procedure is like that which would be employed to investigate backward masking of VC1's by C2V's, and the question arises as to whether general auditory masking might explain the perceptual effect. The aforementioned studies reported results of some stimulus manipulations which argue against the involvement of such masking. The present study explores additional manipulations. Preliminary results suggest the situation to be somewhat more complex than might be supposed from either a masking or articulation-constraint point of view. [Work supported by USPHS Grant No. NS-11647.]
Frequency discrimination with single and multiple observations
Authors: Espinoza-Varas Blas
Published: October 2005

In a “same-different” psychophysical task three experienced listeners discriminated changes in frequency (Δf) that occurred in either of the following stimulus conditions: (1) a single 80- or 160-ms, 1.0-kHz tone burst; (2) in the first or in the second of two successive 80-ms, 1.0-kHz tones separated by intertone intervals of 5, 10, 20, 60, 100, or 150 ms; and (3) in both of the two successive tones described under (2). All stimulus conditions occurred randomly within each block of trials and training proceeded until performance reached asymptote. In the first condition, the value of Δf (d′ = 2.0) was ≈4.0 Hz regardless of tonal duration. For the second condition, the Δf in the first tone required for d′ = 2.0 ranged from 8 to 12 Hz, and that in the second tone ranged from 5 to 7 Hz, depending on the intertone interval. In the third condition the values of Δf (d′ = 2.0) were generally smaller than any of those of the second condition, but still larger than the √ d′ prediction for two independent observations. It appears that within the temporal intervals and experimental conditions of this study, the improvement in performance that is predicted with multiple observations is partly cancelled by temporal interferences that occur between the observations. [Supported by NRC Postdoctoral Fellowship to the author.]
Design of rubber mandrel fiber optic hydrophones
Authors: Jameson Paul , Burton Tom , Ordubadi Afarin , Africk Steven
Published: October 2005

The response of a fiber optic pressure sensor consisting of a long fiber waveguide wrapped azimuthally on a rubber cylinder has been analyzed. The response of the rubber cylinder includes forced waves and free bar waves. The sensitivity of the hydrophone depends on the trace wavenumber of the incident pressure field and therefore is strongly affected by the frequency and the angle of incidence of the sound wave. In addition the temperature of the environment and the frequency of the pressure field affect dynamic properties of the rubber cylinder. Axial stiffeners stabilize the properties of the hydrophone and also reduce the influence of the trace wavenumber of the incident acoustic wave. Two types of design work well, either one with stiffening sufficient to produce a slightly subsonic bar wave, or one with stiffening sufficient to produce a bar wave speed of about four times the speed of sound.
A standard pressure gradient hydrophone
Authors: Henriquez T. A.
Published: October 2005

The Naval Research Laboratory, Underwater Sound Reference Detachment, has developed a standard pressure gradient hydrophone that has a very stable response with hydrostatic pressure to 70 MPa and temperature from 3° to 30°C. The useful frequency range extends from 10 Hz to 8 kHz. The small size of the hydrophone (0.064 m in diameter) allows its use as a reference standard in our low-frequency pressure vessels.
Effect of internal humidity on a sonar transducer
Authors: Cassidy Patrick E. , Rolls Gary C. , Arnett Shawn
Published: October 2005

For several years techniques have been available for the calculation of the rate at which water enters rubber-sealed electronic devices. However, the effect of this internal moisture on the electronic behavior of a transducer was unknown. Further, the disposition of the internal moisture was in question. This study showed that humidity and humid aging change transmitting current response and free-field voltage sensitivity for one sonar transducer. Also, thorough drying of the device can nearly restore the original characteristics. The water in the transducer is ca. 98% adsorbed on surfaces.
Nearfield of a large acoustic transducer, Part I: Linear radiation
Authors: Garett G. S. , Tjøtta J. Naze , Tjøtta S.
Published: October 2005

Results are reported of an investigation of the nearfield of a large circular transducer (diameter 182 cm, and composed of 364 smaller elements operating in water at 11–16 kHz, and with parametric generated difference frequencies in the range 0.5–5 kHz). Linear radiation is considered in this paper, whereas parametric radiation is discussed in an accompanying paper by J. Naze Tjøtta, S. Tjøtta, and G. S. Garrett. Amplitude and phase are measured at various distances and compared with calculations based on a simplified solution obtained by Naze Tjøtta and Tjøtta [J. Acoust. Soc. Am. 68, 334–339 (1980)]. Comparison is also made with an exact on-axis calculation. The main results are (1) the transducer radiates as a piston with a uniform velocity distribution and (2) the parabolic approximation represents an adequate description of the observed soundfield. Formulas are also presented, from which the field of an amplitude or phase shaded source can be calculated in a simple way for the case of axial symmetry. It is further shown how the farfield (amplitude and phase) can be calculated readily from the nearfield measurements. [This work was supported by the Office of Naval Research.]
Benefits of acoustical field diversity sonar
Authors: Lubman David
Published: October 2005

Diversity reception is widely used to protect communication systems from fading due to multipath interference. Four classes of diversity—time, frequency, space, and angle—are now recognized as beneficial for acoustical channels (such as shallow water and long-range sonar). A fifth class—acousticul field diversity—is proposed here. An elementary acoustical field diversity receiver consists of up to four colocated hydrophones. One of these responds to sound pressure and three respond to sound particle motion along orthogonal axes. Performance benefits of an acoustical field diversity sonar are calculated for Rayleigh channels with independent fading. Degradation due to correlated fading is calculated. Theoretical improvements are shown for average SNR, instantaneous SNR, holding time on fading signals, and reliability of data transmission. Experimental confirmation from sea tests is shown.
The diffraction of dipole sound by the edge of a rigid baffle
Authors: Meecham W. C. , Bui T. D. , Miller W. R.
Published: October 2005

The theory of the diffraction of dipole radiation by a half-plane [M. Yildiz and O.K. Marwardi, J. Acoust. Soc. Am. 32, 1685 (1960)] has been much used in aeroacoustics work. There has been little experimental work done on the problem however. We place a small speaker near a half-plane and find an angular distribution which confirms the theory. The half-plane in effect splits the dipole so that the radiation in its direction is enhanced. [Partially supported by NASA-Ames.]
Directivity patterns measured in air for a source in water
Authors: Mikeska E. E. , Shooter J. A.
Published: October 2005

Experimental measurements of the directivity patterns of an underwater sound projector operating at a frequency of 38 kHz were made with a hydrophone in the water and with a microphone in air above the water surface. Three different grazing angles of the projector beam with the water surface were used. The measured patterns in air and in water agree very closly down to the level of the second sidelobes. Making the measurements in air eliminates the problem of a surface reflection for a hydrophone near the air-water interface, allowing source level measurement without interference effects. The price for this freedom is more than 65-dB transmission loss through the interface. The measurement method is thus restricted to cases in which the source level is high enough to allow a sufficient signal-to-noise ratio at the microphone after the transmission loss. [This work was sponsored by the Office of Naval Research.]
A-weighted sound levels of transients of different frequencies
Authors: Young Robert W.
Published: October 2005

A pure sine wave that starts and ends on zero, after passing through the mild bandpass filter known as the A-frequency weighting, is still a pure sine wave shifted in phase, but preceded and terminated by transients which become markedly “impure” as frequency is lowered below 100 Hz. At a given frequency the initial and terminal transients are the same, regardless of the duration of the sineburst. Hence if one wants to measure, say, the rms amplitude of the sinusoidal part of an A-weighted wave, the duration of the original sineburst should be long, so that the inevitable initial and terminal transients do not significantly contaminate the measurement. On the other hand, if one wants to test the capability of an instrument to measure, for example, the fast (125-ms exponential time-average) sound level of an A-weighted transient, the sineburst should be as short as possible (one cycle), so that the sinusoidal part does not significantly contaminate the measurement. As a numerical example of the “impurity” of a terminal transient, for an A-weighted 20-Hz sineburst the observed peak amplitude is nearly 11 times the rms amplitude of the sinusoidal part, regardless of the duration of the sineburst. That is, the crest factor is 11, and equivalent to the theoretical peak-to-rms level of 21.2 dB.
Preliminary results on the performance of a fiber-optic microphone
Authors: Maurer Gregory S. , Cole J. H. , Bucaro J. A. , Blackstock David T.
Published: October 2005

Considerable research has been performed on the use of optical fibers as acoustic sensors. Pressure-induced variations in the fiber's optical properties can be detected by measuring changes in either amplitude or phase of light guided in the fiber. These changes in the guided light can be related to the insonifying field. Most experimental studies to date have involved the use of fibers as hydrophones. Reported here are preliminary results of air-acoustical studies using a loop of optical fiber as a microphone. The loop, having a diameter of 4 cm, contained 10 m of plastic-jacketed, single-mode fiber, and constituted one arm of a Mach-Zehnder interferometer. The loop was insonified at frequencies between 40 and 1100 Hz, where hydrostatic boundary conditions are assumed to be valid. Initial results indicate a response, measured as relative phase change per unit pressure, of 1 × 10−11 Pa−1. Although this response is similar to the underwater result, there are physical reasons for believing that the transduction mechanisms in air are different from those in water. These differences in transduction, and their expected effect on the response of fiber microphones, will be discussed. [This research was supported in part by ARRADCOM and in part by the Defense Nuclear Agency (Task Code B99QAXRB, Work Unit 00011) through the Fiber Optic Sensor System (FOSS) Program.]
Generation of sound by an alternating current in a thin, straight resistive wire
Authors: Wright Wayne M.
Published: October 2005

The generation of acoustic waves through intermittent release of thermal energy in a fluid forms the basis for optoacoustic spectroscopy of gases. A narrow, chopped laser beam, passing through a gas with an optically absorbing constituent, produces an acoustic signal that gives a measure of the constituent concentration. Acoustically resonant gas cells often are used in order to enhance the generally weak signals. In the present work, Joule heating by electrical current in a length of ♯40 manganin wire simulates the absorption of optical energy and serves as a convenient line acoustic source for optimizing the operation of an optoacoustic cell in its first-order azimuthal resonance mode. An average electrical power of 10 mW/cm results in approximately I mPa sound pressure at the 3.8 kHz resonance of a 5-cm i.d. cell (Q ∼ 100) with the electrical current at one-half this resonance frequency. The same ac current at the resonance frequency, with a suitable dc bias current, results in about four times this sound pressure. [Work supported by ONR.]
Ultrasonic power measurements utilizing a microsphere scatterer and the integrated optical effect: Theory
Authors: Love L. Alan , Riley Ward A.
Published: October 2005

Microsphere scatterers have been used with reasonably good success to study the acoustical pressure fields produced by ultrasound transducers [P. L. Edwards, B. D. Cook, and H. D. Dardy, J. Acoust. Soc. Am. 68, 1528–1530 (1980); and P. L. Edwards and J. Jarzyuski, J. Acoust. Soc. Am. 68, 356–359 (1980)]. The theoretical integrated optical effect has been calculated for simple transducers vibrating as pistons. [F. Ingenito and B. D. Cook, J. Acoust. Soc. Am. 45, 572–577 (1969)]. In this investigation, the theoretical integrated optical effect was calculated for spherical waves produced by a small sphere placed in the field of a monochromatic source. The line integral of the acoustic pressure was numerically evaluated for values of the ratio of the light-to-sphere distance (z0) to ultrasonic wavelength (Λ) from unity to 40. The temporal peak value of the pressure integral was found to occur with a phase shift of approximately (+45°) relative to the spherically scattered pressure wave. The value of the pressure integral varied from approximately 0.5 to 0.08 over this range. From these results, it should be possible to experimentally determine the power scattered by the sphere and thus the intensity incident upon the sphere using a recently described optical technique [W. A. Riley, L. A. Love, and D. W. Griffith, J. Acoust. Soc. Am. Suppl. 1 69, S91 (1981)]. This method should be applicable to broadband systems and offers the potential of calibration of high intensity ultrasonic fields. [Work supported by NIGMS 27755].
Threshold shifts induced by exposure to impulse noise with different peak pressures and the same energy density spectrum
Authors: Paterson James H. , Mozo Ben , Hargett C. E. , Lomba Ilia M. , Curd Dennis
Published: October 2005

Current hearing conservation criteria utilize peak pressures as one of the primary measures of magnitude. Peak pressure in conjunction with a measure of duration is translated into an indication of the hazard associated with a given impulse. Historically, it is not difficult to understand why peak pressure was chosen as a basic parameter. It is relatively easily determined. However, the empirical basis for using it as an indicator of auditory hazard goes little beyond the crude correlation between peak pressure and intensity. The experiment reported here directly compared the effects on hearing threshold of impulses with peak pressures differing by 8 dB whose energy density spectra were identical. Twenty-four chinchillas were used as subjects, four groups of six animals each. Group one was exposed to 100 high-peaked impulses at 147-dB peak pressure. Group two was exposed to 100 low-peaked impulses (139-dB peak) which had the same energy density spectrum as the 147-dB high-peaked impulses. Group three received 100 high-peaked impulses at 139-dB peak pressure. Group four was exposed to 100 low-peaked impulses (131-rib peak) with the same energy density spectrum as the 139-dB high-peaked impulses. No statistically significant differences were found between the threshold shifts induced by impulses with the same energy density spectra. However, different levels did produce different degrees of threshold shift.
Acoustic reflex studies on power tool noises
Authors: Smith Marshall M. , Chari Nallan C. A. , Price Lloyd L.
Published: October 2005

The acoustic reflex threshold (ART), latency-, rate-, and magnitude-of acoustic reflex (AR) contraction were measured on 30 subjects using ten power tool noises. The measured values ranged from 78.8 through 81.8 dB SPL for ARTs, 152.0 through 552.5 ms for latency, 0.0009 through 0.0011 cc/ms for rate, and 0.669 through 0.816 cc for magnitude. A discussion on comparison of the above measures to those obtained with a broadband noise will be presented.