bluuebunny/crossref_metadata_2025 huggingface dataset:
Psychophysical Investigation of Auditory Sensitization
Authors: Deatherage Bruce H. , Hendersong Donald , Hafter Ervin R. , Dolan Terrence R.
Published: September 2005

The fact of “sensitization” is well known. In the auditory system, it is demonstrated by a larger amplitude for N1 in response to a click having a condensation followed by rarefaction as opposed to the reverse (Peake and Kiang). The Békésy audiogram also shows fluctuations in threshold as a gated tonal stimulus is slowly moved in phase along a very low-frequency masking tone (Shickman). We have attempted to demonstrate sensitization in a controlled psychophysical setting in which a very low frequency, usually 50 Hz, was adjusted in level to be 5–10 dB below classical absolute threshold. This served as the background; it cannot strictly be called a masker. A brief high-frequency tone was gated coherently with the low frequency and placed in various phase relations to the low-frequency tone. Percent-correct judgments in two-interval forced-choice experiments was the dependent variable. Sensitization was demonstrated. [Work supported in part by the U. S. Office of Naval Research.]
Interaural Intensity Difference Limen
Authors: Rowland Roy C. , Tobias Jerry V.
Published: September 2005

Comparisons were made between three kinds of intensity difference thresholds for the purpose of determining interaural-binaural and interaural-monaural relations. A variation of the Békésy technique was developed for use in these experiments. Five subjects were tested at 250, 2000, and 6000 Hz. At each frequency, responses to 27 intensity combinations were measured. Simple monaural and binaural conditions were included. In addition, each of 24 of the combinations was measured under 0° and 180° interaural phase conditions. Maximum and minimum intensities were 50 and 20 dB HL (ISO). Results indicate that interaural DL's decrease as a function of level, as might be predicted. These thresholds vary as a function of frequency and apparent azimuth of the fused tone, but are relatively insensitive to variations in interaural phase. Interaural intensity-difference thresholds are more properly compared with monaural than with binaural DL's.
Phase Vocoder
Authors: Flanagan J. L. , Meinhart D. I. S. , Golden Roger M. , Sondhi Man Mohan
Published: September 2005

A type of vocoder is described that promises modest bandsaving and elimination of the pitch-tracking and voiced-unvoiced switching inherent in spectrum channel vocoders. A speech signal f(t) suffers little degradation when passed through a parallel bank of contiguous bandpass filters and then recombined. If fn(t) is the output of the nth bandpass filter, the original signal f(t) is approximated by Σnfn(t). Each fn(t) can be represented by two parameters: the value of the short-time amplitude spectrum of f(t) evaluated at frequency ωn, and the time derivative of the short-time phase spectrum also evaluated at ωn. These data are transmitted to a synthesizer that produces approximations to each fn(t). The complex short-time spectrum calculated for each channel is F(ωn,t) =  ∫ −∞∞ ∫ (λ)h(t−λ)e−jωnλdλ=|F(ωn,t)|eiφ(ωn,t), where h(t) is the impulse response of a realizable low-pass filter. The amplitude |F(ωn,t)| and the phase derivative φ̇(ωn,t) are formed for each channel, low-pass-filtered and transmitted to the sythesizer. At the synthesizer, φ̇(ωn,t) frequency-modulates an oscillator of nominal center frequency ωn, and |F(ωn,t)| amplitude-modulates the same oscillator. The synthesized signals for all n channels are then summed. In effect, the |F(ωn,t)| signals carry the spectral envelope information, and the φ̇(ωn,t) signals carry the excitation information. Previous experience with channel vocoders shows that the |F(ωn,t)| signals may be band-limited to around 20 cps. Our experiments with the phase vocoder indicate that the φ̇(ωn,t) signals may be similarly band-limited. Speech transmitted by the phase vocoder is demonstrated.
SPASS—An Improved Terminal-Analog Speech Synthesizer
Authors: Tomlinson Raymond S.
Published: September 2005

A new terminal analog or resonance speech synthesizer has been developed combining analog and digital computation techniques. The signal-processing speed of analog circuits is merged with the symbolic and arithmetic manipulation flexibility of digital computers to provide performance surpassing that possible with strictly analog, or strictly digital techniques. The familiar cascaded-pole synthesizer is realized by ordinary analog-computer methods, with circuit coefficients determined by digital multipliers controlled from a small digital computer. The experimenter exercises control over the synthesizer with a series of commands typed on a typewriter console. By this method, an utterance may be synthesized, judged, modified, and tried again in rapid succession. The data specifying an utterance may be entered from prepared paper tapes, by fitting polynomials to points entered through the typewriter, or by drawing the required data with a “light pen” on a CRT display. An algebraic statement interpreter is included to process input data and facilitate generating regular utterance sequences. [Work supported in part by the U. S. Air Force Cambridge Research Laboratories.]
Effects of Multiple Vocoderization on Consonant Intelligibility
Authors: Cohen Marion F. , Voiers William D.
Published: September 2005

The diagnostic rhyme test was used to investigate the effects of multiple vocoderization of speech on intelligibility of initial consonants. The results indicate a relation between the discriminability of a particular articulatory feature and its vowel context. Moreover, the nature of this dependency may vary as a function of the manner in which the speech is processed. [Research reported in this paper sponsored (in part) by the U. S. Air Force Cambridge Research Laboratories, Office of Aerospace Research.]
Further Developments in Unit-Variance Scaling Method
Authors: Mickunas J.
Published: September 2005

It was reported at a previous meeting that a unit-variance scale was developed to evaluate preference for vocoder-processed speech. More-recent studies indicated that distances between vocoders varied in different contexts but that their relative scale differences remained constant. Four representative vocoders were selected as standards and tested in different contexts. Unbiased psychological distance functions were normalized among different contexts to give a standard preference scale that was independent of the testing context. Additional vocoders were compared with the standard vocoders and their distances adjusted to the standard preference scale. [Research reported in this paper sponsored (in part) by the U. S. Air Force Cambridge Research Laboratories, Office of Aerospace Research.]
Spectra of Large Underwater Explosions
Authors: Hamilton G. R. , Patterson Brian
Published: September 2005

The line structure present in the spectra of small underwater explosive charges, due to interference between shock wave and bubble pulse, has often been observed. Signals received at Bermuda from two recent large underwater explosions exhibit similar characteristics. These two signals originated from the detonation of Liberty ships loaded with surplus explosives and scuttled in deep water off the East Coast. The first was an unscheduled detonation of the USS VILLAGE, loaded with 7000 gross tons of explosives and scuttled on 17 September 1964. The sink time was 4 min. Clear bubble pulse lines at 2.75-cps spacing and an estimated sink velocity of 1000 ft/min indicate a 300-ton, TNT equivalent, yield. The 15 July 1965, Chase III event was a planned seismic experiment to detonate 600 tons, equivalent TNT, at 1000 ft. Poor bubble-pulse lines spaced 6/10 cps apart indicate a 600-ton explosion at 1000-ft depth.
High-Intensity Air-Modulator Noise Source
Authors: Eldred Kenneth McK.
Published: September 2005

This paper develops the basic elementary theory for the modern air-modulator noise source that operates at pressure ratios equal to or greater than the critical pressure ratio required for sonic nozzle flow. The results are compared with the low-pressure siren theory of R. C. Jones [J. Acoust. Soc. Am. 18, 371 (1946)], and it is shown how sonic nozzle flow produces a surprisingly linear high-pressure noise source. The theory examines the acoustic relationships of all of the noise-source parameters, utilizing a mass-flow analogy, and the results are compared with experimental data.
Vibration of Partially Fixed Beams Carrying an Arbitrary Number of Concentrated Masses
Authors: Amba-Rao Chintakindi L.
Published: September 2005

The problem of the vibration of beams with partial fixity, carrying an arbitrary number of concentrated masses, has evinced considerable interest in recent years. The true edge-fiixity conditions for beams in airplane and space vehicle structures are far from the idealized conditions; the idealized conditions are simple supports and fully fixed. In the following note, three different methods, all closed-form (not series) solutions of analysis for the solution of a partially fixed beam, with unequal end fixities and an arbitrary location of a mass, are presented. The methods utilize (1) finite Fourier sine transforms, (2) finite Laplace transforms, (3) matrix methods. The eigenfrequencies for two special cases with partial fixities are numerically calculated on a computer, employing the first method.
Effects of Motion on Sound Generation
Authors: Lowson Martin V.
Published: September 2005

Most high intensity acoustic sources are in motion relative to the undisturbed atmosphere. This paper presents improved methods for calculating the sound generated by sources in arbitrary motion. A number of examples are presented, the principal current applications being to problems of forces on a rotating system such as on a fan or helicopter. General expressions for simple sources, forces, and acoustic stresses in motion are given. It is found that the effects of acceleration is to cause additional, higher-order terms in the radiated sound field. A derivation of the basic results was given earlier [Proc. Roy. Soc. (London) A286, 559–582 (1965)].
Low-Binary-Data-Rate Operation of the Formant Vocoder
Authors: Campanella S. J. , Coulter D. C.
Published: September 2005

One of the formant vocoder's principal promises lies in the more efficient encoding of the word information content of speech than can be achieved by the use of the more familiar channel vocoder. The consequence of this more efficient encoding manifests itself in the capability for encoding speech for binary-encoded formant data at binary-data rates potentially as low as 150 bits/sec. In this paper, various avenues of approach for achieving such low-binary-data-rate transmission are explored for system operation at various data rates ranging from 150 to 1200 bits/sec. Results of recent laboratory tests are presented.
Holographic Visualization of Sound Fields, Using Lasers
Authors: Stetson Karl , Elion Herbert A.
Published: September 2005

Holography, which is a photographic process for recording and reconstructing electromagnetic fields, is a motion-sensitive process. As such, it can be used to detect motions of diffuse three-dimensional surfaces with interferometric accuracy. The implication to acoustics is that an experimental tool has been developed that makes easily available previously unobtainable information about vibration geometries and amplitudes.
Theory of the Generation of Intense Hypersound by Lasers
Authors: Chiao R. Y.
Published: September 2005

Brillouin scattering, or the scattering of light by sound waves, can become a stimulated process under the sufficiently intense excitation now possible with laser sources. This effect can be viewed as a parametric interaction of light and sound. Thus, amplification and generation of intense hypersonic waves are possible. The kinematics and the dynamics of this process will be studied, starting first with some elementary energy considerations and later with coupled wave equations.
Propagation Path of a Wave in a Variable-Speed-of-Sound Medium Obtained by Employing Fermat's Principle
Authors: Solomon L. P.
Published: September 2005

By application of Fermat's principle, the ray path of a sound wave in a variable-speed-of-sound medium is derived using variational techniques. This approach leads to an integral that gives the horizontal position of the wavefront explicitly as a function of the speed-of-sound variation. It is assumed that the speed-of-sound is a function of depth only. For the ocean, it is shown that a hyperbolic cosine closely approximates the actual speed-of-sound variation with depth. With the aid of this approximation, solutions of the ray-path integral can be obtained in closed form.
Phase Spreading in Directly Transmitted Sound-Wave Packets
Authors: Lord Norman W.
Published: September 2005

A short sound pulse, transmitted horizontally between two points in deep ocean water, arrives at the receiver as a continuous superposition of time-separated wavepackets. This fact has been demonstrated by a detailed analysis of the crosscovariance between such pulses carrying a phase reversal and a truncated replica. In all, about 280 pulses were selected from over 3000 that were previously studied [N. W. Lord, J. Acoust. Soc. Am. 36, 1043(A) (1964)] for the transmission time fluctuation. For these 1200-cps pulses, the phase spreading becomes tangible at a range of 7 km, where it is approximately π/3, or about 0.2 msec. As an estimate of instantaneous phase spread, this value is reasonable as compared to the transmission-time fluctuation, for this range, of 0.7 msec between pulses spaced every 0.6 sec. The use of a truncated replica on a long pulse depresses most of the side-lobe crosscovariance peaks. The magnitude of the central peak is related to both the phase spreading and the chosen length of the truncated replica, although this latter dependence is lost by a slow phase reversal. Hence, for these measurements, if Δ is the phase spread, the magnitude of the crosscovariance peak is (sinΔ)/Δ. At ranges under 7 km, Δ is small and the peak is close to unity with small fluctuation. At ranges over 7 km, the peak declines and fluctuates more among the successive pulses. [Hudson Laboratories of Columbia University Informal Documentation No. 108. Work supported by the U. S. Office of Naval Research.]
Phase Change Associated with Total Internal Reflection at a Strong Negative Gradient
Authors: Parkes D. J.
Published: September 2005

During an investigation of convergence-zone propagation in the Mediterranean, it was remarked that the explosion-pulse arrivals, which had suffered refraction at the extremely strong negative gradient near the surface, had been subjected to a drastic change of pulse shape. The first arrival that had suffered one deep refraction but no shallow refraction showed no evidence of change of pulse shape, except the normal broadening owing to absorption. The pulses were sampled and Fourier transforms were made, revealing that a phase-change independent of frequency of the order of π/2 had occurred in the case of arrivals with one shallow turning point, and one of the order of π for those with two shallow turning points. Theory predicts a phase change of π/2 on total internal reflection at an inhomogeneous layer and this could well be the cause of the effect observed; however, no evidence of phase change at the deep turning point has been found.
Solution of the Waterborne Multipath Problem through Correlation Techniques
Authors: Duback Earl
Published: September 2005

The purpose of this paper is to illustrate a method for separating waterborne acoustic paths, using correlation techniques. The physical setup consisted of three hydrophones and an underwater speaker at a “quiet” test facility. The signals were recorded simultaneously on an FM tape recorder. The tape recordings, filtered from 200 to 2000 cps to avoid aliasing, were digitized at 7200 samples/sec, introduced into the Univac 1107 computer, and the correlation, power, and phase functions obtained. The crosscorrelation between the speaker and hydrophone separates the direct and indirect signal according to their time of arrival. The section of the correlogram containing the direct signal is considered, while all other values are set to zero; then, the power and phase associated with this section are determined. The section containing the indirect signal is given similar consideration. Mathematical descriptions of the power and phase are found to be in good agreement with these experimental results.
Sound Fields at Long Ranges in Shallow Water
Authors: Mackenzie K. V.
Published: September 2005

Measurements were made in 25-f (fathom) water with 15-min CW tones of 350-, 700-, and 1300-cps sound transmitted from an anchored ship. Sound was received on an anchored vertical string of 14 hydrophones spaced 10 ft apart. Measurements were made at ranges of 5, 10, 20, and 40 kyd. The thickness of the subbottom over the transmission paths had been previously surveyed acoustically. During the earlier survey, a number of bottom samples were obtained to determine the sound speed, attenuation, and density of the sediment. Explosive transmission data were obtained just after the CW measurements were made and these have been reported [J. Acoust. Soc. Am. 36, 251–258 (1964)]. The mean signal level at each hydrophone can be determined with an estimated accuracy of 1 dB. These mean levels define the CW sound field. The sound fields exhibit a definite dependence on hydrophone depth and vary as much as 20–30 dB from surface to bottom. In general, the sound level decreases significantly near the bottom of all conditions. The signal-level fluctuations and frequency spreading agreed with earlier measurements [J. Acoust. Soc. Am. 34, 67–75 (1962)].
Characteristics of Ambient Noise off Bermuda
Authors: Weigle F. G.
Published: September 2005

The data resulting from a 23-month ambient-noise measurement program are reviewed. 2-min-long broad-band magnetic tape recordings were made every 2 h, from omnidirectional hydrophones at fixed locations. Ten noise-level readings were made in each of ten logit frequency bands between 100 and 1000 cps from each recording. The mean value obtained from each set of ten readings was taken as the representative level of that 2-min sample in subsequent data processing. The data clearly show the dependence of ambient-noise level upon wind-speed and a lesser dependence upon wave height. The spectrum is seen to change markedly with wind speed and to suggest the presence of both wind-dependent and non wind-dependent mechanisms. Level-distribution histograms show dependence upon both frequency and season. The standard deviation is shown to be a function of both frequency and wind speed. Power-spectrum analyses indicate the occurrence of cyclical noise variations with periods up to 55 h.
Turbulent Boundary-Layer Pressure Fluctuations on the Surface of a Body of Revolution at High Reynolds Numbers
Authors: Franz Gerald J.
Published: September 2005

The power-spectral densities of the boundary-layer pressure fluctuations on the surface of a large body of revolution are presented in dimensionless form. The pressure fluctuations were measured with small flush-mounted hydrophones and the boundary-layer displacement thicknesses were measured with adjustable pitot tubes. A transition region between laminar and turbulent flow was observed on the nose of the body. The spectra of the pressure fluctuations in this region differ in several respects from similar spectra for flat-plate turbulent boundary layers in air; the levels are higher at low frequencies and lower at high frequencies and the signals are intermittent in character. The spectra of the pressure fluctuations behind the transition region are more or less the same as those for flat plates.
Feedback Effects of Audition and Vocal Effort on Intensity of Voice
Authors: Alpert Murray
Published: September 2005

Variations in sidetone gain and in ambient-noise level were found to produce changes in the intensity of voice that were in the direction of constant S/N ratios at the talkers' ears. However, the magnitude of the changes was small and the data fit a model of constant voice level as well as a feedback model. An indirect analysis of the effects of vocal effort on vocal intensity was done, based on the assumption that vocal effort would be proportional to vocal intensity. No evidence was found for feedback control of voice level based on vocal effort. The narrowness of the range of voice levels produced by each subject, in contrast with the wide range of auditory stimulation, suggests that talkers have important nonauditory mechanisms for the control of voice level. Voice-level control, then, appears to depend on both auditory feedback and nonauditory nonfeedback mechanisms.
Relationship between Linguistic Units and Motor Commands
Authors: Fromkin Victoria A.
Published: September 2005

The semicontinuous acoustic signal that we call speech is the result of a number of discrete neuromuscular events. We cannot store in our brain motor commands for every utterance that we may wish to say, owing to the brain's finite storage capacity. Speech then is produced by the rearrangement of a limited number of stored items. What is the size of nature of these stored units? How do speakers encode a sequence of discrete linguistic units into a continuously changing speech signal? An electromyographic study revealed that no simple correspondence exists between a phoneme and its motor commands. Initial and final allophones of consonants differed; both were unaffected by the adjacent vowels. Vowels were influenced by the preceding consonant. The results of this study relevant to the relationship between motor commands and phonetic segments are discussed. Alternative hypotheses relating to the nature of the stored unit are suggested.
Speaker Variation and Vocal-Tract Size
Authors: Mattingly Ignatius G.
Published: September 2005

The hypothesis that differences in the formant-frequency value sets among speakers of the same dialect are owing chiefly to variation in individual vocal-tract size was tested on the Peterson-Barney formant-frequency data. For three speaker classes—men, women, children—the distribution of values for each of three formants of each of ten vowels was correlated with every other such distribution. The hypothesis implies that the correlation scores should be high. Actually, most scores were low, though interesting subsets (F2 with F3 for each front vowel, F1 with F2 for each back vowel, F3's with one another for children) were high. Furthermore, the separation between male and female distributions for some vowel formants is much sharper than variation in individual vocal-tract size can reasonably explain. The variation within class must be stylistic, not physical; and the difference between male and female formant values, though doubtless related to typical male and female vocal-tract size, is probably a linguistic convention.
Power Relations in the Violin Family
Authors: Schelleng John C.
Published: September 2005

The relative power capabilities within the family of bowed-string instruments are examined, attention being given to the conventional instruments as well as to the new series demonstrated in the Saunders memorial concert. As a whole, these instruments form a series of nearly constant stiffness.
Violin Design
Authors: Engstrom G. E.
Published: September 2005

The elements for the design of a violin are developed. Parabolic surfaces are used for the inside and outside of the plates. Plate thicknessces are determined from the characteristics of the wood actually being used. The assumptions made in determining the frequencies of the enclosed air, top, and back are discussed. A bass-bar design is presented having uniform stress along its length. An example of a violin design is given.
Equivalent Circuit of the Guitar
Authors: Bartolini William
Published: September 2005

Experiments performed on a guitarlike enclosure indicate that the equivalent circuit of this instrument is that of a bass-reflex enclosure augmented by a series-resonant element (the back) in parallel with the air volume and the port. The soundboard and back plates of the enclosure are removable and replaceable with rigid panels. Either plate can be driven by a moving-coil transducer with low mechanical mass. The assembled enclosure also can be played. Up to one octave above the box resonance frequency, the frequency response curve of the enclosure shows the characteristic three peaks found in instruments of the violin family. As in the simple bass-reflex enclosure, the ratio of the frequencies of the two lower peaks is determined by the ratio of the acoustic mass of the soundboard to that of the port. Wide spacing of these peaks corresponds to low acoustic mass of the soundboard and louder, more-responsive instruments.
Clarinet-Reed Parameters
Authors: Backus John
Published: September 2005

The detailed harmonic structures of loud tones sounded on the clarinet depend in part on certain physical parameters associated with the clarinet reed. Six such parameters have so far been found that influence the tone to some degree. (1) The stiffness of the reed determines the ease of blowing the instrument. This fact is, of course, well known to reed-instrument players, who customarily scrape reeds to produce a suitable stiffness. (2) The mass of the vibrating tip of the reed, together with the stiffness, determines the resonance frequency of the tip, which influences the higher harmonics of the tone. (3) The damping of the material of the reed also has an effect on the higher harmonics. (4) The gap between the tip of the reed and the tip of the mouthpiece has some effect on the ease of blowing. (5) The amount of leakage past the reed in its closed position during the cycle affects the higher harmonics. (6) The impact of the vibrating reed against the mouthpiece produces impulses that are transmitted to the teeth and thence by bone conduction to the ears of the performer. This produces a buzz that is heard by the player as part of the tone. In addition to the six items enumerated above, there may be other factors not yet isolated.
Approach to Electronic-Organ Design
Authors: Marler Donald D. , Dwyer Samuel J.
Published: September 2005

Electronic-organ sounds have lacked the “warmth” and beauty of pipes, as reported by Dr. Harvey Fletcher and others. Also, the electronic instruments do not imitate pipe organs sufficiently in sound and operation so that performing artists may be comfortable with and artistically challenged by them. Therefore, electronic-organ design should begin with analysis of pipe organs. Harmonic analysis was performed on the sound produced by a total of 36 organ pipes from 5 stops. Charts show the average harmonic patterns for each stop and the observed standard deviations. The range of harmonic patterns within each stop was not great enough to destroy its stop identity, although many deviations were aurally detectable. This indicates that each note in a synthetic rank need not, and perhaps should not, have an identical tonal structure. Electronic synthesis of the flute and principal harmonic patterns was approximated through waveshaping and a linear combination of simple waveshapes from octave sources.
Articulatory Information from Acoustic Data
Authors: Schroeder M. R.
Published: September 2005

The extraction of articulatory information from acoustic data is an attractive alternative to cineradiographic methods for studying articulation during connected speech. However, two major difficulties complicate the transformation from acoustic to articulatory descriptions: uncertainty of the vocal excitation function and nonuniqueness of the vocal-tract area function (for a given transfer function). Methods for overcoming these difficulties are described. A particularly promising approach is based on a recently discovered unique relation between the area function of a smooth tract and the impedance function at the lips. Area functions obtained from speech spectra and impedance functions are illustrated and compared with the x-ray data. The potential of new acoustic-analysis techniques as a supplement to and substitute for x-ray analysis is evaluated.
Studies of Articulatory Activity during Speech Production
Authors: Stevens Kenneth N.
Published: September 2005

Investigations of the configurations and motions of the speech-generating mechanism during an utterance provide data that can be related in a reasonably direct fashion both to the acoustic signal that results from these motions and to the linguistic description that underlies the utterance. Results of several studies of cineradiographic films of speech and of airflow and pressure events in speech show that simple articulatory correlates of the features associated with a given phoneme maintain an identity when the phoneme is embedded in various environments, whereas the acoustic correlates of these features are apparently more complx and are more dependent upon the phonetic environment. Studies of the relations between articulatory activity and the resulting speech sounds can be used to provide insight into the invariant set of acoustic attributes or cues that characterize a given phoneme.
Computer Simulation of Spherical Nearfield Measuring Array for Farfield-Pattern Predictions
Authors: Murphy Donald A.
Published: September 2005

A network of linear systems whose inputs are nearfield pressures measured on the surface of a sphere and whose summed output is the desired farfield pressure has been simulated on the digital computer. The transfer functions for these linear systems were calculated from the normal derivative of the Green's function of the scalar wave equation as suggested by Ferris [J. Acoust. Soc. Am. 38, 933(A) (1965)]. These “Green's transfer” functions have a particularly satisfying physical realization. They consist of time delays plus amplitude shading. They have a linear frequency dependence and no theoretical bandwidth limitation. Patterns of an infinitesimal dipole source have been calculated, using the Green's transfer functions to determine the accuracy of their farfield predictions. Errors in this pattern were determined as functions of frequency, probe spacing, and the angle between radius vectors to the nearfield and farfield points. The reciprocal nature of the measuring system was investigated by using it as a source and calculating its ability to produce a plane wave inside the measuring surface. [Work supported by U. S. Navy Bureau of Ships.]
Near Field of a Dipole for Measurements in Shallow Lakes or Tanks
Authors: Bobber Robert J.
Published: September 2005

When acoustic measurements are made in a shallow lake or tank, reflections from the boundaries produce serious interference in the sound field at frequencies below about 2 kHz. If a dipole (two out-of-phase simple sources) is used as a projector, substantial sound-pressure level is available in the near field, regardless of the well-known inefficiency of such projectors. At the same time, interference caused by lateral reflection is virtually eliminated by the farfield cosine pattern and that caused by longitudinal reflection is reduced by the inefficiency or low farfield response. Curves show the nearfield sound pressure as a function of dipole size, test distance, boundary geometry, and frequency. Experimental data illustrate elimination of interference in a shallow lake.
Some Computed Effects of a Concentric Elastic Shell on the Farfield Characteristics of a Cylindrical Transducer
Authors: Moyer W. C. , Tucker E. A.
Published: September 2005

Analytical expressions for the sound pressure produced by a cylindrical transducer radiating within a concentric, elastic shell are derived. The cylindrical transducer is divided into a series of strips, each of which radiates with a prescribed velocity amplitude and phase. The analytical expressions can be used to determine the influence of the shell on the nearfield and farfield sound-pressure distributions of the transducer. This paper includes some computed results for farfield directivity patterns of transducers with and without shells and the dependence of familiar measures of transducer performance such as directivity index, side-lobe level, and major beamwidth on the parameters of the transducer-shell model. The parameters include transducer-shell spacing, shell thickness and density, and shell-material properties. The latter results are presented as functions of dimensionless variables formed as products of the parameters of the transducer-shell model.
Improvement of Transducer Characteristics through Multiplicative Processing
Authors: Bennett M. S. , Allen D. E. , Barnard G. R.
Published: September 2005

A multiplicative receiving array that combines electronic signal processing with multiplication, using a Hall-effect multiplier, was tested for directionality and minor-lobe suppression. Both farfield and nearfield characteristics were studied. The farfield data obtained indicated that the multiplicative processing narrows the half-power beamwidth of the 85 kHz, 20-in. line array from 1.8° to 0.7° and reduces the level of the minor lobes from −13 to −29 dB. Theoretical beam patterns calculated for the array are compared to the beam patterns obtained experimentally. As expected, the multiplicative processing resulted in some degradation of the signal-to-noise ratio of the hydrophone; however, this degradation of signal-to-noise does not seem prohibitive in view of the improvements gained with this technique. [Work sponsored by the U. S. Office of Naval Research.]
Hydrophone-Preamplifier Optimization
Authors: Lukman Frank J.
Published: September 2005

In any system, a number of hydrophone-preamplifier combinations are capable of meeting the design parameters; however, the choice of an optimum design is not always obvious. This paper presents an approach by which an optimum design may be obtained. Since the output signal-to-noise ratio of the preamplifier is a function of hydrophone sensitivity and capacity, which in turn are functions of hydrophone dimensions, it is apparent that an optimum hydrophone-preamplifier combination might be arrived at by combining preamplifier characteristics with hydrophone characteristics. This paper outlines a computer approach to this problem and shows the results. A typical case is presented that considers a multielement array where both size and weight are important. A set of equations and curves is generated whereby different sized hydrophones are placed under a common denominator and evaluated on a relative basis. Finally, these results are combined with a preamplifier producing a set of signal-to-noise output contours from which an optimum hydrophone-preamplifier may be selected. This concept has been proved on a recently completed project. One interesting result was the combination of a pair of hydrophones in series at the input of each preamplifier. This is contrary to normal practice of two units used in parallel addition.
Useful Formulas for Piezoelectric Ceramic Resonators and Their Application to Measurement of Parameters
Authors: Onoe Morio , Jumonji Hiromichi
Published: September 2005

Electrical characteristics of a lossless ceramic resonator with fully covered electrode can be expressed by three basic parameters: clamped capacitance, electromechanical coupling factor, and the gravest resonant frequency or antiresonant frequency. Unified formulas are derived for various modes of vibration with longitudinal and transverse electric field. The formulas are valid for a very wide range of frequency, but the calculation is not simple because of transcendental functions involved. Hence, approximate formulas are derived that are simple and easy to calculate. The accuracy of the approximation is far better than the accuracy of conventional lumped-constant equivalent circuit representation. A novel method for determining three basic parameters of a ceramic resonator with transverse electric field is developed based on the present approximate formulas. The method requires only the measurement of resonant frequencies, before and after the insertion of a series capacitance, and eliminates the need for both the measurement of antiresonant frequency and the measurement of low-frequency capacitance, which are required in a conventional practice.
Multiple-Mode Piezoelectric Resonators
Authors: Onoe Morio
Published: September 2005

As a vibrator of continuum medium, a piezoelectric resonator has an infinite number of eigenmodes. Most resonators, however, have utilized one and only one mode of vibration. Novel quartz and ceramic resonators utilizing more than one mode have been developed. Such a resonator is useful as a filter element, because characteristics of a full lattice network with resonators in each arm can be realized by a single resonator. The frequency separation between modes to be utilized should be within the design limit of filters owing to the capacitance ratio of the resonator. Their motional inductances should be approximately equal in order to realize symmetrical bandpass characteristics. Their temperature coefficients should be approximately equal in order to realize a good stability. These criteria can be met by the following modes, which practically cover all the frequency range of interest. For the use at a high frequency, symmetric and antisymmetric trapped energy modes of thickness vibration in a thin plate are suitable. Quasidegenerative modes of longitudinal and flexural vibrations in a plate are useful at a medium frequency, while quasidegenerative modes of two mutually perpendicular flexural vibrations in a rod are useful at a low frequency.
Instrumental Effects on the Brillouin Spectra
Authors: LaMacchia J. , Leidecker H.
Published: September 2005

A monochromatic, collimated light beam is body-scattered by a transparent liquid or solid into a spectrum consisting of a Rayleigh line having the incident frequency and symmetrically displaced Brillouin lines whose displacement measures the sound velocity in the medium and whose width measures the sound absorption. The nonzero width of the incident light spectrum, the nonzero bandpass of the spectrum analyzer, and the overlapping of the Rayleigh and Brillouin lines appreciably distort the observed spectrum, introducing serious errors into velocity and absorption values These effects are discussed, and practical means of correction established.
Accuracy and Precision of Hypersonic-Velocity Measurements, Using the Stimulated Brillouin-Scattering Technique
Authors: Carome E. F.
Published: September 2005

The stimulated Brillouin light-scattered technique is being used for measurements of the velocity of hypersound in liquids. Details of the experimental procedure and the precision of the results are presented in terms of extensive data obtained over relatively large temperature ranges in dichloromethane and benzene. [Work supported in part by the U. S. Office of Naval Research and the Advanced Research Projects Agency.]
Temporary Theshold Shifts in the Auditory Sensitivity of the Chinchilla after Exposure to Low-Frequency Noise
Authors: Miller James D. , Rothenberg Stephan J.
Published: September 2005

Three monaural chinchillas were exposed to noise (300–600 Hz, 100-dB SPL) for an effective duration of 193 min. The experiment was replicated six times each at two-week intervals. Tests of quiet thresholds at 715 Hz were interspersed within each exposure. Threshold levels increased from 0- to 38-dB SPL with the logarithm of exposure duration. Postexposure audibility curves were uniform across low frequencies but increased to maximum at 2.0 kHz for two of the animals. All thresholds returned to normal in about 48 h. Two chinchillas were then exposed to this noise for seven days. Thresholds measured during brief quiet periods increased during the first day of exposure and remained about constant thereafter. After completion of the exposure, threshold shifts were found throughout the audible range and they recovered nearly to normal in about one week. However, small permanent threshold shifts are probably present below 1 kHz. [Work supported by the National Institutes of Health, Public Health Service, U. S. Department of Health, Education, and Welfare.]
Analyses of Auditory-Nerve Action Potentials in the Chinchilla
Authors: Eldredge Donald H.
Published: September 2005

Teas, Eldredge, and Davis [J. Acoust. Soc. Am. 34, 1438–1459 (1962)] proposed a model for the physiological and electrical properties of whole-nerve action potentials recorded with cochlear electrodes in the guinea pig. Action potentials for clicks were differentially disrupted by bands of noise with constant spectrum level as the high-pass frequency of the noise was lowered. The incremental changes in waveform resembled action-potential waveforms occurring at successively later times and corresponding to known traveling-wave delays. The model was supported by the changes observed following localized chemical injuries in the cochlea and by the ability of the model to predict the waveform elicited by bursts of high-frequency tones. The method has been applied to the chinchilla in an improved form with a LINC computer. Similar relations are observed and further support for the model is found in the altered relations associated with anatomically verified lesions of the cochlea. [Work supported by National Institutes of Health, Public Health Service, U. S. Department of Health, Education, and Welfare.]
Negative dc Potential in Scala Media during Early Stage of Anoxia
Authors: Konishi Teruzo , Kelsey Elizabeth , Singleton George T.
Published: September 2005

Negative potential in scala media during nearly anoxia was recorded in both normal and kanamycin-treated guinea pigs. In kanamycin-treated animals, in which the pseudothreshold of the cochlear microphonic was remarkably elevated, decline of the dc potential was slower and its negative value smaller than in nontreated animals. After prolonged anoxia, polarity of the negative potential could be changed by application of positive pressure to scala vestibuli, whereby the postmortem cochlear microphonic was enhanced. When the potential drop at the hair-bearing ends of hair cells was increased by an external source of current, amplitude of postmortem cochlear microphonic was increased. However, neither application of pressure nor current produced any enhancement of cochlear microphonic after the negative potential in scala media reached zero. These data indicate that the negative dc potential in the scala media during early stages of anoxia is produced by depolarization of the hair-bearing ends of the hair cells and that the stria vascularis is sensitive, while the hair-bearing ends of the hair cells are insensitive to oxygen deprivation.
Cochlear Potentials in the Kangaroo Rat
Authors: Vernon Jack , Herman Paul
Published: September 2005

The cochlear potentials for the kangaroo rat display an unusual sensitivity to the low frequencies. This animal also possesses extremely large bullae to which some investigators have attributed enhancement of low-frequency tones. Attempts to reveal the function of these bullae by electrophysiological measures are discussed.
Single-Unit Activity in Primary Auditory Cortex of Unanesthesized Cat
Authors: Goldstein M. H. , Hall J. L.
Published: September 2005

Activity of single cells in cats immobilized with gallamine triethiodide was recorded with metal microelectrodes and displayed by an on-line dot display. Tone-burst, noise-burst, click, and swept-tone stimuli were presented through condenser microphones at both ears. Spontaneous activity ranged from less than one spike per second to greater than 40 spikes per second. Almost all cells were affected by acoustic stimuli, either by enhancement of activity, reduction of activity, or a combination. Cells were affected at the onset and/or termination of a stimulus, throughout a stimulus, or a combination. Best frequency of cells ranged from less than 1 kHz to greater than 50 kHz. The pattern of response to tone bursts of some cells changed as the frequency of the stimulus was changed. The activity of some cells was closely related to the slow-wave potential at the electrode tip, but for others there was little relationship. Subsurgical doses of sodium pentobarbital greatly reduced both spontaneous and evoked unit activity. [Work supported in part by the Public Health Service, U. S. Department of Health, Education, and Welfare, and by the U. S. Air Force Office of Scientific Research.]
Inhibition of Evoked Auditory Responses during Avoidance Learning
Authors: Saunders James C.
Published: September 2005

Inhibition of “nonrelevant” auditory evoked potentials (AEP) by “relevant” stimuli in another sense modality was investigated in a controlled behavioral situation. Behavioral performance during the acquisition of an instrumental response to a “relevant” stimulus cue was compared to the degree of inhibition observed in the neural response to an “irrelevant” stimulus. Neural responses to continuous click stimuli were measured at the cochlear nucleus and the auditory cortex of a cat subject as it learned an avoidance response to a visual cue. Inhibition was defined as a decrement in the AEP's during the presentation of the visual cue. The results indicate inhibition of the cortical AEP during acquisition of the conditioned response and disappearance of inhibition with overlearning. The AEP at the nucleus showed inhibition only in the middle of acquisition performance. Unexpectedly, there was a gradual attenuation of the noninhibited nucleus response during the course of learning. This long-term “habituation effect” could be selectively removed or introduced by the presence or absence of the behavioral task. The results were interpreted in terms of “attentive” qualities of the visual cue and its effect on inhibition.
Sound Pressure Generated in an External-Ear Replica by a Nearby Point Source
Authors: Teranishi R. , Shaw E. A. G.
Published: September 2005

A physical replica of the external ear has been mounted in a large rigid plane. A point source of sound is placed a few centimeters from the earcanal entrance and at any desired angular position. The sound pressure at selected positions in the external ear is measured with a probe-tube microphone over the frequency range 1–15 kcps. The ratio of earcanal pressure to reference pressure measured at a reflecting plane surface is substantially independent of source distance for d⩾8 cm. Response curves at the eardrum are markedly dependent on angle of incidence above 4 kcps. A well-defined resonance at 2.8 kcps is measured at all positions in canal and concha. The concha alone has a very broad quasilongitudinal (depth) resonance at 4–6 kcps and transverse resonances above 9 kcps.
Earcanal Pressure at Hearing Threshold with Varying Acoustic Field
Authors: Shaw E. A. G.
Published: September 2005

A well-damped circumaural encolsure may be fed by any one of five acoustic driver units located at cardinal positions. The acoustic field at the ear may thus be varied in a manner corresponding to variation in angle of incidence. Acoustic pressure at a well-defined position in the earcanal is measured with a probe tube passing under the circumaural cushion. For each subject and frequency, earcanal pressure at hearing threshold is determined using the five driver units in turn. Preliminary measurements with three subjects show average threshold pressure variations with driver position of ±0.7, ±1.7, and ±1.0 dB at 5, 8, and 12.5 kcps, respectively. At each frequency and for each subject, excellent correlation between earcanal pressure and airborne stimulus, independent of acoustic field, is indicated.