摘要:

At audible frequencies, the vibrational relaxation of nitrogen contributes significantly to the absorption of sound in still air. The accurate measurement of the humidity dependence of the relaxation frequency of nitrogen, as yet, has eluded careful measurement due to the difficulty in measuring small absorption at low frequencies. Recently, equipment has been constructed for measuring sound absorption in air as a function of humidity over the frequency range from 4 to 100 kHz. In the experiment described here, the temperature and humidity range of this equipment has been extended so that it can be used to study the relaxation absorption in nitrogen at temperatures from 311° K to 418° K. The results indicate that, over this temperature range, the frequency of maximum absorption in moist nitrogen,fr,n, can be given byfr,n/P=260×h, Hz/atm, wherehis the percent mole fraction of water, andPis the pressure in atm. To the accuracy of the measurements reported here,fr,nis independent of temperature over the range of temperatures at which the measurements were made.

ISSN:0001-4966    

DOI:10.1121/1.381557

出版商:Acoustical Society of America    

年代:1977

数据来源: AIP

摘要:

The temperature and frequency dependence of the ultrasonic absorption coefficient in molten selenium have been studied in the range from 200° to 400° C and from 30 to 70 MHz. The data are consistent with the values in the literature for the high‐temperature range but supersede the previous results below 300° C. A theoretical model is prepared in which the monomer (rings) of the selenium represent a nonrelaxing component with the polymer chains forming a relaxing component.

ISSN:0001-4966    

DOI:10.1121/1.381558

出版商:Acoustical Society of America    

年代:1977

数据来源: AIP

摘要:

The three‐mode theory due to Mindlin and McNiven, [J. Appl. Mech. 27, 145–151 (1960)] governing axisymmetric motions in a circular rod, is appraised by comparing responses predicted by it with experimental data obtained by Miklowitz and Nisewanger [J. Appl. Mech. 24, 240–244 (1957)]. The problem studied involves a semi‐infinite rod, made of 24S‐T aluminum alloy, subjected to pressure applied to the end of the rod. The two sets of responses are compared at various stations along the rod. To make the comparisons meaningful, it was necessary to recognize that the pressure applied experimentally had a finite rise time, however short; to make an estimate from the responses of what that rise time might be; and then apply this time distribution of pressure in evaluating the theoretical responses. Comparison shows that the Mindlin–McNiven theory predicts the responses at stations farther than one diameter from the end of the rod. The matching is accurate not only at the head of the impulse but at points representing large times following the first disturbance.

ISSN:0001-4966    

DOI:10.1121/1.381559

出版商:Acoustical Society of America    

年代:1977

数据来源: AIP

摘要:

General, nonlinear equations are derived for the vibration of rectilinear tubes conveying incompressible fluid. From these equations are obtained the equations for small vibrations. If values of tube frequencies and critical flow parameters are to be predicted accurately, the initial state of stress must be taken into account. A numerical example is considered.

ISSN:0001-4966    

DOI:10.1121/1.381560

出版商:Acoustical Society of America    

年代:1977

数据来源: AIP

摘要:

Acoustical scale model experiments carried out with building‐size barriers are described. The results of experiments conducted with the barrier in a free field and on a reflecting surface are presented. The free‐field measurements are compared to several theoretical models and discrepancies between the theoretical and experimental results are discussed. Also presented is a simple expression which relates the excess attentuation obtained with the barrier situated on the ground to that of the same barrier in the free field. This expression predicts excess attenuations which agree quite closely with those actually measured in the scale model experiments.

ISSN:0001-4966    

DOI:10.1121/1.381561

出版商:Acoustical Society of America    

年代:1977

数据来源: AIP

摘要:

The perception of dichotic chords is characterized by two unique properties—invariance of the relative salience of the two pitch components with respect to large interaural intensity differences (’’intensity independence’’) and a tendency for the tone delivered to one ear to be relatively more salient (’’ear dominance’’) [Efron and Yund, J. Acoust. Soc. Am. 59, 889–898 (1976)]. A simple model is described which can account for these effects and the changes in the magnitude of these effects as a function of stimulus parameters. The model assumes (1) the existence of tuned frequency specific monaural filters, (2) a compressive intensity‐response function, and (3) a central combination of corresponding monaural channel responses. The model’s performance is not only consistent with all previously published experimental data but also anticipates experimental results described in the two companion papers.

ISSN:0001-4966    

DOI:10.1121/1.381562

出版商:Acoustical Society of America    

年代:1977

数据来源: AIP

摘要:

The relative salience of the two pitch components (the pitch mixture) of a two‐tone dichotic chord (one tone to each ear via earphones) has been shown to be invariant with respect to the interaural intensity difference (ΔI) over a wide range of ΔI[Efron and Yund, J. Acoust. Soc. Am. 59, 889–898 (1976)]. This range of invariance of the pitch mixture was systematically studied as a function of absolute signal level and signal‐to‐noise ratio. Results indicate that a decrease in the signal‐to‐noise ratio and a decrease in the sound‐pressure level both served to decrease the range of interaural intensity differences over which the invariance occurs. However, while a decrease in both parameters decreased the range of intensity independence, there was a strong interaction between these parameters: The addition of noise eliminated the effect of sound‐pressure levels. These findings are discussed in the context of the model described in the companion paper [Yund and Efron, J. Acoust. Soc. Am. 62, XXX–XXX(1977)].

ISSN:0001-4966    

DOI:10.1121/1.381563

出版商:Acoustical Society of America    

年代:1977

数据来源: AIP

摘要:

Frequency‐discrimination thresholds were determined for pure tones presented either to the right or to the left ear of experienced listeners. In some conditions the stimulus was monaural, whereas in others a tone of fixed, different frequency was simultaneoulsy present in the contralateral ear. Center frequencies of 1.2, 1.7, and 3.2 kHz were investigated. Results reveal a small but reliable discrepancy between just noticeable frequency differences obtained for the right and for the left ear, both in the monaural and in the dichotic conditions. Furthermore, the direction and the degree of asymmetry with respect to the frequency resolving power of the two ears showed a correlation with the direction and the degree of ear dominance for the pitch of dichotic two‐tone complexes. [See Efron and Yund, J. Acoust. Soc. Am. 59, 889–898 (1976).] Implications of the relationship between the two types of functional asymmetry of the auditory system are discussed.

ISSN:0001-4966    

DOI:10.1121/1.381564

出版商:Acoustical Society of America    

年代:1977

数据来源: AIP

摘要:

In an earlier paper [J. Acoust. Soc. Am. 50, 1116–1122 (1971)] I presented a lateralization model of binaural masking‐level differences (MLD’s), according to which detection under conditions which produce an MLD is based on the average value of an interaural parameter, Δ. This factor is made up of interaural time (Δt) plus interaural intensity (ΔI) weighted by a binaural trading ratio (TR). Two figures in that paper depicted application of the model to MLD’s found as a function of frequency [(Hirch and Burgeat, J. Acoust. Soc. Am. 30, 827–832 (1958)]; those figures are partially incorrect. They show the lateralization equation with a time‐intensity trading ratio of 20 μsec/dB to be the best fit, when in fact, the fit to TR=0 μsec/dB is excellent. The lateralization model with a trading ratio of 0 is very much like the vector model of Webster [J. Acoust. Soc. Am. 23, 452– 462 (1951)]and Jeffressetal. [J. Acoust. Soc. Am. 28, 416–426 (1956)]. It is suggested here that variability in the noise process may be significant factor, allowing binaural neurons tuned to high frequencies to recover and then respond again to interaural differences of time.

ISSN:0001-4966    

DOI:10.1121/1.381565

出版商:Acoustical Society of America    

年代:1977

数据来源: AIP

摘要:

The absolute threshold for two‐component tone bursts of 500‐msec and 1‐sec duration was measured as a function of the frequency spacing between the components. The average frequency of the two components was 700 Hz. When interpreted in terms of an energy‐detector model (peripheral filter followed by squarer, integrator, and threshold detector), the measurements give an estimate of the time constant and window shape of the integrator. Our measurements on two subjects give a time constant on the order of 200 msec. A window which initially decreases more rapidly than exponentially fits the data better than an exponential window.

ISSN:0001-4966    

DOI:10.1121/1.381566

出版商:Acoustical Society of America    

年代:1977

数据来源: AIP