摘要:

Much can be learned about the molecular properties of liquids and solutions from investigations concerning acoustic velocity and attenuation. However, systematic studies are needed. Sound velocities in aqueous solutions ofLi2SO4, Na2SO4, KHSO4, K2SO4, (NH4)2SO4, andMgSO4were measured over wide ranges of concentration and over the temperature range 0 to 80°C. It was found that the sound velocityversustemperature curves rise and are displaced toward lower temperatures with increase in concentration. Except at concentrations above about one molar the curves are, within the limits of experimental error, the same as the displaced curve for water. The specific acoustic impedance of these sulfate solutions varies linearly with concentration at 20°C. Adiabatic compressibilities are well represented by an empirical expression. Relative association was found to rise with increase in concentration. This is because of solvation of the ions in solution. From the available data apparent molal compressibilities were computed for the temperature range 15 to 35°C.

ISSN:0001-4966    

DOI:10.1121/1.1907819

出版商:Acoustical Society of America    

年代:1959

数据来源: AIP

摘要:

Expressions for the mutual radiation impedance coefficient are derived in the cases of uniformly vibrating circular and rectangular acoustic sources on a rigid spherical baffle. Numerical results for circular sources on a sphere are given as a function of the source separation for several values ofka(ais the radius of the sphere andkis the wave number). The interaction between circular sources on a large sphere and on a plane is compared numerically.

ISSN:0001-4966    

DOI:10.1121/1.1907820

出版商:Acoustical Society of America    

年代:1959

数据来源: AIP

摘要:

For a number of years it has been known that flexural vibrations in a plate can be damped by the application of a layer of damping (viscoelastic) material that is in turn constrained by a backing layer or foil. A common example is the damping tape currently used in aircraft.This paper presents a quantitative analysis of the damping effectiveness of such a constrained layer. As in the work of H. Oberst the damping is characterized by the loss factor η, which is the normalized imaginary part of the complex bending stiffness of the damped plate.The calculated damping factor depends on the wavelength of bending waves in the damped plate, and on the thicknesses and elastic moduli of the plate, the damping layer, and the constraining layer. A complex shear modulus is assigned to the damping layer, where all of the energy dissipation is assumed to take place.Damping factors have been determined experimentally on laboratory test bars for a number of constrained‐damping‐layer applications for frequencies from about 100 to 4000 cps over a range of temperatures. Gratifying agreement with calculated damping has been found for variations in frequency, temperature, and damped‐bar geometry.

ISSN:0001-4966    

DOI:10.1121/1.1907821

出版商:Acoustical Society of America    

年代:1959

数据来源: AIP

摘要:

The fundamental frequencies of flexural vibration are determined for uniform isotropic square plates that have pinpoint supports at the four corners and flexible beams along the edges. The flexible beams are pinned to the plate so that the beams resist only deflection of the plate boundaries. Finite difference solutions, which simplify the treatment of the boundary conditions for definite values of Poisson's ratio, are used to obtain the approximate solutions.

ISSN:0001-4966    

DOI:10.1121/1.1907822

出版商:Acoustical Society of America    

年代:1959

数据来源: AIP

摘要:

The damaging potential of mechanical shock experienced by resiliently mounted equipment is discussed in general terms. It is pointed out that the displacement, relative displacement, and acceleration of the mounted item, expressed as nondimensional quantities, describe the likelihood of damage in particular circumstances.The performance of mounting systems has been judged by their response to a step‐like shock displacement. The nondimensional quantities above have been determined as functions of the steepness of the leading edge of the step displacement for one‐ and two‐stage, linear, viscously damped spring mountings. Heavy damping is beneficial in a mount in several respects, and its adverse effects on transmitted acceleration can be mitigated by the use of the two‐stage mountings.

ISSN:0001-4966    

DOI:10.1121/1.1907823

出版商:Acoustical Society of America    

年代:1959

数据来源: AIP

摘要:

The results of some practical measurements on the effects of interchannel intensity and time differences in two channel (stereophonic) sound systems are presented. The effects of alterations in the listener position are also covered. The test signals used ranged from single component tones to wide and narrow band noise and included running speech. A theory based on the assumption that the brain is sensitive to interaural time difference and its variation with head movement is developed and is shown to be in reasonable agreement with the practical findings.

ISSN:0001-4966    

DOI:10.1121/1.1907824

出版商:Acoustical Society of America    

年代:1959

数据来源: AIP

摘要:

Noise bands simulating passive sonar sounds were varied in terms ofspectrum(band passed from 150–600 cps, or 600–2400 cps, or 2400–9600 cps); in terms of amplitude modulation (simulated screw beats) atbeat ratesof 0, 3, 5, or 11 per second; and in terms of presence or absence ofaccentwithin a group of 4 beats. Every combination of these parameters (21 in all, not 24, since at zero beat rate there can be no accent) was rated by 20 subjects in terms of their aurally perceived characteristics on 15 scales representing seven different dimensions.Analysis was made of the manner in which the 21 sounds clustered within the space defined by the seven psychological dimensions. Two major clusters of sounds were observed, differentiated primarily on the basis of band pass condition (high frequencyvslow frequency). Exceptions to this general rule were analyzed to reveal the interactions between band pass condition, beat rate, and accent.

ISSN:0001-4966    

DOI:10.1121/1.1907825

出版商:Acoustical Society of America    

年代:1959

数据来源: AIP

摘要:

An extension of a method originally employed by Békésy in 1933 was used to estimate the velocity of the traveling wave along the cochlear partition. The method consists of masking a different length of the basilar membrane at each of the two ears so that the wave produced by a simultaneous click at the ears emerges from the shorter masked portion of one ear sooner than from the other. As a result the click lateralizes toward the side where the wave emerges sooner. The time interval by which the click to the “earlier” side must be delayed to center the subjective click is an estimate of the original difference in time of emerging from the masking and hence of the time taken to travel the portion of the membrane represented by the difference in cutoff frequency of the two masking noises. Measurements were taken for 14 overlapping half‐octave segments of the basilar membrane on 7 subjects. Measurement was not possible below 1000 cycles with the instrumentation used. The velocity estimates range from 55 m/sec near the stapes to approximately 30 m/sec at a point some 20 mm away.

ISSN:0001-4966    

DOI:10.1121/1.1907826

出版商:Acoustical Society of America    

年代:1959

数据来源: AIP

摘要:

Although encouraging progress has been made in the measurement of loudness, certain objections to the sone scale have been raised from time to time. This paper tries to answer some of these objections, and especially to show how the form of the sone scale can be verified by cross‐modality matchings. Instead of working with numerical estimations of magnitudes or ratios, these new procedures allow observers to equate the apparent intensity of stimuli in two different sense modalities. It turns out that the results of these cross‐modality matches can be predicted from the relation between the sone scale and the subjective scales in the other modalities. These experiments strengthen the evidence for the validity of the sone scale. They also suggest that the form of the subjective intensity function depends on the “input‐output” operating characteristic of the sensory system and not on some prior experience which the observer may have had with a “physical correlate” of the stimulus.

ISSN:0001-4966    

DOI:10.1121/1.1907827

出版商:Acoustical Society of America    

年代:1959

数据来源: AIP

摘要:

The initial rate, extent, and recovery from auditory adaptation were measured in both the presence and absence of noise in ten normal ears by the method of fixed intensity at 250, 1000, and 4000 cps. It was found that the initial rate and extent of adaptation to a tone in noise were greater than to the tone alone at 4000 cps, but not at either 250 or 1000 cps. Recovery from adaptation to tones in both noise and quiet was found to be equivalent, but never complete, at each frequency. When the noise was sustained in one ear and a tone introduced over the noise at 1‐min intervals, there was a systematic decline in response at 250 and 1000 cps, but not at 4000 cps. When the noise was not sustained, but followed the same periodic intervals as the tone, there was a decline in response at 4000 cps, but not at either 250 or 1000 cps.

ISSN:0001-4966    

DOI:10.1121/1.1907796

出版商:Acoustical Society of America    

年代:1959

数据来源: AIP