摘要:

We report in this paper some results on ultrasonic absorption and velocity of selected low loss liquids and mixtures which may improve the resolving power of the scanning acoustic microscope. We have investigated the effect of electrolytes as a solvent in water which serve to lower the value of α/f2of water. We also report on our results with hydrogen peroxide and carbon disulfide for these two liquids should allow us to improve the resolution by more than a factor of 2.Subject Classification: [43]35.24.

ISSN:0001-4966    

DOI:10.1121/1.380827

出版商:Acoustical Society of America    

年代:1976

数据来源: AIP

摘要:

Westinghouse is developing two different types of sonic cameras for real time imaging in turbid water. A 2‐MHz side‐look sonic camera has been built for viewing the ocean bottom at angles from 35° to 55°. The plane of the bottom is mapped into an image plane behind the lens. Ninety‐eight line transducers are used in the image plane to form 98 simultaneous beams. Range resolution is determined by time, as in a side‐look sonar, and angular resolution is determined by the lens. A 25‐cm lens obtains resolutions of 1.5 to 6 cm at ranges from 3 to 12 m. A circular‐scan camera has been built to operate at 3 MHz. This camera maps a plane orthogonal to the direction of view into the image plane behind the sonic lens. The image is swept out by a row of 128 transducers rotating in the image plane. A 27‐cm lens makes it possible to achieve resolutions of 1 to 3 cm at ranges from 3 to 9 m. Lens data applicable to both cameras is given and initial pictures taken with both types of cameras are shown.Subject Classification: [43]35.80; [43]30.80; [43]35.65.

ISSN:0001-4966    

DOI:10.1121/1.380828

出版商:Acoustical Society of America    

年代:1976

数据来源: AIP

摘要:

A simple frequency equation is derived for the in‐plane vibration of thick rings, taking account of the effects of transverse shear and rotatory inertia. The remarkable accuracy of the expression is demonstrated by comparison with experimental data.Subject Classification: [43]40.26.

ISSN:0001-4966    

DOI:10.1121/1.380829

出版商:Acoustical Society of America    

年代:1976

数据来源: AIP

摘要:

The changes in the resonance frequencies of circular crystal plates subject to initial bending stresses are studied. The plate is flexed as a cantilever clamped near the edge and stressed by a transverse, concentrated force applied at a point diametrically opposite the support. A system of plate equations which takes into account the nonlinear effects due to the large, initial deflection and to the third‐order elastic stiffness coefficients in the stress–strain relations is employed. In obtaining the initial fields caused by bending, strain components are assumed to be small, but large gradient of plate deflection and large rotations of the plate element aboutx1andx3axes are permissble by retaining their quadratic terms in the strain‐displacement relations. The changes of resonance frequencies of fundamental thickness‐shear vibrations are calculated for rotatedYcuts of quartz. The calculated frequency changes are compared with experimental values as a function of the force position, the azimuth angle ψ, and also as a function of the magnitude of thr forceP.Subject Classification :[43]40.24.

ISSN:0001-4966    

DOI:10.1121/1.380830

出版商:Acoustical Society of America    

年代:1976

数据来源: AIP

摘要:

Range‐distributed targets are often characterized as arrays of point scatterers. This conceptualization corresponds to a target impulse response that is a sequence of impulses. A physically meaningful generalization of this description is obtained by modeling an impulse response in terms of pulse doublets, impulses, step functions, ramp functions, etc., i.e., as a superposition of delayed impulsesanddifferentiated or integrated impulses. A sonar system for generalized target characterization is derived in this paper. Signals and receivers are specified for (1) optimum estimation of reflector parameters and (2) detection of a known target in clutter. The derived signals correspond closely with some of the waveforms that are used by dolphins and bats for echolocation. The corresponding echo analyzers are similar to psychoacoustic models of the mammalian hearing system.Subject Classification: [43]60.20, [43]60.50; [43]30.82; [43]80.50.

ISSN:0001-4966    

DOI:10.1121/1.380831

出版商:Acoustical Society of America    

年代:1976

数据来源: AIP

摘要:

A software‐oriented adaptive null‐processing technique for underwater acoustic arrays has been developed and applied to experimental data obtained from a 20×20 square array. This method, which involves spatial homodyning, is holographic in nature, with important similarities to both DICANNE and a recent holographic enhancement technique. The approach is described and evaluated, compared with other methods, and results obtained from its application to experimental underwater data are presented. The technique removes the side lobes from a source image as well as the main lobe in the null direction; a striking example of this in an underwater experiment is given.Subject Classification: [43]60.30; [43]35.65; [43]30.82.

ISSN:0001-4966    

DOI:10.1121/1.380840

出版商:Acoustical Society of America    

年代:1976

数据来源: AIP

摘要:

Average discharge rate of single auditory‐nerve fibers in cats was measured in response to one‐ and two‐tone stimuli. One component (the ’’suppressor tone’’) of each two‐tone stimulus was at a frequency (f2) which produced two‐tone suppression at some stimulus levels. The other component (excitor tone) produced an increase in rate above the spontaneous rate when presented alone. Fractional response was defined as the driven rate to the two‐tone stimulus divided by the driven rate to the excitor alone. Fractional response is thus a quantitative measure of the amount of suppression produced by a suppressor tone. A number of qualitative differences were found in the dependence of fractional response forf2≳CF andf2

ISSN:0001-4966    

DOI:10.1121/1.380841

出版商:Acoustical Society of America    

年代:1976

数据来源: AIP

摘要:

A model of hair cell excitation that involves mechanical impact between the hair cells and the tectorial membrane has been proposed by Crane [J. Acoust. Soc. Am. 40, 1147–1154 (1966); J. Acoust. Soc. Am. 51, 508–514 (1972)]. The model predicts that if the impact is unilateral, biasing of the basilar membrane toward or away from the tectorial membrane will significantly affect the generation of nonlinear combination tones. Anf2−f1envelope tone synchronized with thef1andf2primaries was used to achieve such biasing. The experiment reported here investigates the effect of the phase of thef2−f1tone on the prominence of the beating of a 2f1−f2combination tone (generated by input primariesf1andf2) and a probe tone that differs in frequency by a few hertz from the frequency of the combination tone. The input thus consists of four explicit tones:f1,f2,f2−f1, and (2f1−f2)+δ. It was found that thef2−f1tone can have a large effect on the level of the 2f1−f2combination tone. The phases of thef2−f1tone that lead to a maximum and minimum level of combination tone are approximately 180° apart, and there can be almost total discrimination between those two phase conditions.Subject Classification: [43]65.56, [43]65.28, [43]65.60.

ISSN:0001-4966    

DOI:10.1121/1.380842

出版商:Acoustical Society of America    

年代:1976

数据来源: AIP

摘要:

In previous work (e.g., Durlach and Braida, 1969; Braida and Durlach, 1972), we have implicitly assumed that sensitivity in absolute identification of sound intensity is independent of the payoff matrix. There are a number of reasons, however, to question the validity of this assumption. For example, if the payoff matrix causes the subject to focus his attention on a particular subrange of stimuli at the expense of the remaining stimuli, the sensitivity between pairs of stimuli in this subrange might be increased relative to the sensitivity between pairs of stimuli outside this range. This paper reports the results of a series of experiments designed to test the above‐mentioned assumption. On the whole, the results are consistent with this assumption. The only significant exception is that, for one of the five subjects tested, the total sensitivity varies with the payoff matrix (in a manner that appears unrelated to the specific properties of the payoff matrix). Also, the observed changes in response bias associated with the changes in payoff matrix are generally in the same direction as, but somewhat smaller than, the changes in bias that would occur in an optimal Bayes receiver.Subject Classification; [43]65.75, [43]65.50.

ISSN:0001-4966    

DOI:10.1121/1.380843

出版商:Acoustical Society of America    

年代:1976

数据来源: AIP

摘要:

The effects of direct variation in static middle ear pressure were studied in the acute guinea pig. Pressure differences of from −500 to +500 mm of H2O were examined. Pure tones were delivered to the test ear in a closed system and the sound pressure levels monitored with a condenser microphone and probe tube situated 2 mm from the tympanic membrane. The cochlear microphonic was recorded from a round window electrode. Both the relative impedance change and cochlear microphonic were noted at various middle ear pressure levels. The animals were perfused with Prussian blue and cochleas stained with osmic acid and prepared for histopathological study. It was found that negative pressure causes greater changes on impedance and transmission than positive pressure. Increase in positive pressure was found to cause a monotonic increase in input impedance and decrease in transmission. For negative pressures, the effect was nonmonotonic. Observed changes in transmission with both positive and negative pressures could be accounted for only in part by changes in input impedance of the middle ear. Morphological findings showed some discrete dilation of the vessels on the malleus and the tympanic membrane.Subject Classification: [43]65.24, [43]65.40.

ISSN:0001-4966    

DOI:10.1121/1.380845

出版商:Acoustical Society of America    

年代:1976

数据来源: AIP