摘要:

Am inproved underwater earphone, insensitive to depth, has been developed following the theoretical approaches reported earlier [B. B. Bauer and E. L. Torick, “Calibration and Analysis of Underwater Earphones by Loudness Balance Method,”J. Acoust. Soc. Amer.39, 35–39 (1966)]. This new transducer offers good efficiency and yields speech reproduction comparable to most air acoustic earphones. The earphone design provides tympanic, rather than bone‐conduction sensing, thereby providing directional signal information to the listener. Pairs of these devices have been used successfully in a directional communication system for underwater swimmers. Threshold levels and some man‐earphone equal loudness contours were obtained for this device.

ISSN:0001-4966    

DOI:10.1121/1.1977570

出版商:Acoustical Society of America    

年代:1971

数据来源: AIP

摘要:

A study of the resonances of a violin was made by attaching an electric pickup to the strings of a normal violin and passing the signal so obtained through a set of electrical resonances. Frequencies, bandwidths, and amplitudes of the resonances could easily be adjusted and resulting sound evaluated aurally. About 20 resonances were used. The frequencies were set equal to the peaks of a published response curve of a Stradivarius. Amplitudes could be adjusted so the tone matched a range of instruments from an orchestral violin to a hillbilly fiddle. Bandwidths from 7 to 100 Hz were tried, about 50 Hz being best. Components of the sound due to individual resonances were heard separately. Low‐frequency resonances gave a rich but muffled tone, midfrequency resonances a thin sound, and the high‐frequency resonances a harsh penetrating sound.

ISSN:0001-4966    

DOI:10.1121/1.1977577

出版商:Acoustical Society of America    

年代:1971

数据来源: AIP

摘要:

When stop consonant‐vowel syllables, 390 msec in duration, are presented dichotically, with an onset asynchrony of 50–70 msec, subjects identify the temporally lagging stop more accurately than the leading. When the same pairs are presented monotically, the leading stop has the advantage. This difference has been interpreted in terms of central versus peripheral masking [M. Studdert‐Kennedy, D. Shankweiler, and S. Schulman, J. Acoust. Soc. Amer.48, 599–602 (1970)]. Dichotically, the signals travel separate peripheral pathways, and central masking effects are revealed. Monotically, the lagging signal is masked peripherally by the overlapping leading signal. This experiment was designed to determine the effect that the elimination of the temporal overlap would have on the dichotic and monotic masking functions. Syllables 75 msec long were presented at six asynchronies between 0 and 100 msec. The dichotic masking function was unaffected, whereas the monotic lead advantages were substantially reduced at the nonoverlapping asynchronies. Implications of these results will be discussed. [Work supported by NIH.]

ISSN:0001-4966    

DOI:10.1121/1.1977583

出版商:Acoustical Society of America    

年代:1971

数据来源: AIP

摘要:

Earlier experiments had shown that dichotically presented stops are more often identified correctly when they share place of production (e.g.,/ba, pa/) or voicing (e.g., /ba, da/) than when neither feature is shared (e.g., /ba, ta/). We interpreted this as further evidence for the perceptual reality of phonetic features. It is possible, however, that the advantage of sharing a feature has an auditory rather than a phonetic basis. We therefore compared the increments due to feature sharing, for synthetic stop‐vowel syllables in which formant transitions were the sole cues to place of production, under two experimental conditions: (1) when the vowel was the same for both syllables in a dichotic pair, as in our earlier studies, and (2) when the vowels differed. If the increment in performance due to sharing place is not diminished when vowels differ (so that formant transitions do not coincide), we can conclude that it accruesafterthe process of feature extraction and therefore has a phonetic rather than an auditory basis. [Research supported in part by grant from NICHD.]

ISSN:0001-4966    

DOI:10.1121/1.1977584

出版商:Acoustical Society of America    

年代:1971

数据来源: AIP

摘要:

It has been suggested that one of the factors that hampers effective work by divers is the lack of good communications. To test this notion, we conducted an experiment that alternated matched teams in a complex underwater construction task. Site of the research was TEKTITE‐2, U. S. Virgin Islands. Two four‐member teams matched in ability but unused to working with each other and unused to using communication systems served as subjects. The work task consisted of assembling a mini‐DICORS (132 parts) in 20 ft of low‐visibility water. On the first trial, members of Team A wore Aquasonics 420 units; Team B had no communication gear. On the second trial (a day later), the communicators were worn by Team B. Time of assembly and number and type of errors constituted the objective measures. In all cases, the performance of the teamwithoutthe communication gear was superior. It was concluded that to be aided by communication systems (1) divers must be trained in their use; (2) they must be allowed to develop appropriate communication procedures; and (3) systems with better intelligibility than those currently available must be obtainable.

ISSN:0001-4966    

DOI:10.1121/1.1977613

出版商:Acoustical Society of America    

年代:1971

数据来源: AIP

摘要:

Nonlinear effects cause demodulation of a pulsed carrier such that a signal proportional to the second time derivative of the square of the pulse envelope develops in the insonified medium. Several different types of pulse envelopes, i.e., rectangular, triangular, and trapezoidal, were utilized to modulate a 455‐kHz carrier. The projector was a 3‐in.‐diam circular piston located at a depth of 10 ft in a fresh‐water lake. A low‐pass filter was used to eliminate any of the carrier frequency signals not absorbed by the water. The amplitudes and beam patterns of the self‐demodulated waveforms were measured. [This work was sponsored by the U. S. Navy Office of Naval Research and the National Science Foundation.]

ISSN:0001-4966    

DOI:10.1121/1.1977629

出版商:Acoustical Society of America    

年代:1971

数据来源: AIP

摘要:

An investigation is made of the effect of the beam pattern of a source exciting an acoustic surface scatter channel using the Fresnel‐corrected geometric‐optics approximation. Results are presented for monochromatic and impulsive excitation using both deterministic and random boundaries. In the random case non‐Gaussian statistics are permitted for the surface deformations. This study concentrates on the limits of very narrow‐ and very broad‐beam patterns and specular geometry at moderate grazing angles. The results for the broad‐beam pattern are found to be simpler than the corresponding ones for narrow‐ and intermediate‐beam patterns. The theory is applied towards the calculation of impulse response convolutions and bifrequency spreading functions. An attempt is made to relate current and past physical results in a nomenclature suitable for application in signal processing and communication theory.

ISSN:0001-4966    

DOI:10.1121/1.1977632

出版商:Acoustical Society of America    

年代:1971

数据来源: AIP

摘要:

The dynamic response of a piezoelectric ceramic microphone, supported on soft rubber washers, was mathematically modeled at three levels of refinement in order to understand the damping mechanisms that control the voltage output. First, a direct variational procedure was used to identify the parameters that govern the lowest system resonances and the low‐frequency sensitivity of the microphone. Then, an exact solution with a lumped‐parameter model of the support structure was formulated and compared to the experimentally obtained voltage output, as a function of acoustic driving frequency. Finally, a finite element solution was obtained, with the support configuration modeled precisely, and compared to experimental results. The analyses were hampered, to some extent, by an inadequate thermomechanical characterization of the rubber material. By making reasonable assumptions about the thermorheological behavior of the rubber, however, adequate agreement with experiment was shown. The ramifications of the analyses for using soft rubber supports to control the response of microphones over a wide temperature range are discussed.

ISSN:0001-4966    

DOI:10.1121/1.1977638

出版商:Acoustical Society of America    

年代:1971

数据来源: AIP

摘要:

A classic problem of acoustics is: How can one build a violin having a tone quality that matches the tone of a Stradivarius? This problem has been under enthusiastic attack for many years by a group of researchers led originally by the late Professor Frederick A. Saunders of Harvard, and more recently by Carleen M. Hutchins. The group calls itself “The Catgut Acoustical Society” and has four hundred members in fourteen nations. Many of the members have achieved professional distinction as mathematicians, physicists, and musicians.Forty years of work in a multidisciplinary situation involving technical researchers, violin makers, performing musicians, conductors, and composers as well as listeners have yielded a vast store of information on the conventional violin, viola, cello, and string bass. Many of these findings have been incorporated into experimental instruments built and tested by Carleen Hutchins in her basement laboratory and workshop resulting not only in improvements in conventional violins, violas, cellos, and basses but also in design and construction of a whole new family of eight violin‐type instruments which give a uniform tone quality across the entire range of musical frequencies.These eight new instruments are to be played by musicians of the National Gallery Orchestra and Mrs. Hutchins will lecture briefly.

ISSN:0001-4966    

DOI:10.1121/1.1977642

出版商:Acoustical Society of America    

年代:1971

数据来源: AIP

摘要:

It is shown that the pressure at any pointPin space generated by an impulse applied over a line or surface can be thought of as the summation of pressure responses due to each element of line or surface, where the “directivity pattern” of each element on this source surface is secθ, θ being the angle between the line from the source element to pointPand the line or plane tangent to the curve or surface at this element. Examples of sources include an infinite plane, a line, and a disk. Further, it is shown that, for the disk, the on‐axis response can be written without calculation, and in addition the Fourier transform can be performed, again without calculation.

ISSN:0001-4966    

DOI:10.1121/1.1977644

出版商:Acoustical Society of America    

年代:1971

数据来源: AIP