摘要:

The mean‐square displacement of a uniform, stretched string, restrained against lateral movement at the boundaries by springs, to a convected, random‐loading field has been investigated. A modal‐analysis technique based on Powell's method has been used, all crosscoupling terms being retained. The response is strongly affected by two parameters: the ratio of convection velocity to the wave velocity of the string (u/a) and the ratio of wavenumber of the excitation to wavenumber of the eigenfunction of the string (ke/ks). Modal response to a harmonic convected wave is greatest for all modes, except the first, when the ratios are both unity. For the first mode, the response is greatest when (u/a) approaches +∞ and (ke/ks) approaches 0 so that the product remains unity. The response is strongly affected by crossproduct terms, even though orthogonal eigenfunctions are used. Inclusion of the crossproduct terms in the calculations results in a mean‐square displacement that is less peaked at the center of the string but correspondingly higher toward the outer ends than if these terms had been neglected. The effect of the boundary flexibility is to increase the mean‐square displacement at all points of the string, and also to make the distribution of this displacement more uniform over the length.

ISSN:0001-4966    

DOI:10.1121/1.1919049

出版商:Acoustical Society of America    

年代:1964

数据来源: AIP

摘要:

Most of the world's major nations, with the exception of the United States of America, have sound‐insulation requirements in their building codes. The purpose of this paper is to describe the experience of several European countries with such requirements. Typical procedures in common use are discussed: there are several variations in the basic definition of sound insulation, the method of interpreting test results, and, finally, the method of influencing or controlling building practice. An important consideration is the information to be gained from various possible types of test. Experience indicates the desirability of three stages of testing for a new type of construction: (1) laboratory tests on individual components; (2) tests on a partial assembly of wall and floor sections; and (3) tests on the completed structure. At each stage, problems are usually found that had not been anticipated earlier.

ISSN:0001-4966    

DOI:10.1121/1.1919051

出版商:Acoustical Society of America    

年代:1964

数据来源: AIP

摘要:

Most of the existing sound‐insulation requirements are based on experience with traditional construction, and this is reflected in the shape of the standard grading curve. Since nontraditional constructions frequently have quite different sound‐insulation characteristics, the desired shape of insulation curve, i.e., the relative importance of the various frequency bands, becomes an important consideration. To gain insight on this point, the problem was approached by considering directly the activities and needs of apartment dwellers. The tentative conclusion is that the most common type of grading curves, including the ASTM Sound Transmission Class curve, are of approximately the correct shape for rating sound insulation between dwellings.

ISSN:0001-4966    

DOI:10.1121/1.1919053

出版商:Acoustical Society of America    

年代:1964

数据来源: AIP

摘要:

Because of increasing complaints of disturbance from impact noise in multifamily dwellings, the Federal Housing Administration plans to include in their Minimum Property Standards some recommendations for the control of this noise. A study of the existing noise codes and several surveys of public reaction to household noise has led to (1) the recommendation of a criterion of acceptability for floor/ceiling constructions in multifamily dwellings; a listing of floor/ceiling structures commonly used in the U S A, classified as to their ability to meet the criterion, and (2) a set of recommendations and suggestions regarding important structural details. This paper gives the results of that study and tells how they were arrived at.

ISSN:0001-4966    

DOI:10.1121/1.1919055

出版商:Acoustical Society of America    

年代:1964

数据来源: AIP

摘要:

Stress is laid on the lack of adequate acoustical treatment in the design and construction of multiple dwellings in the United States of America.

ISSN:0001-4966    

DOI:10.1121/1.1919057

出版商:Acoustical Society of America    

年代:1964

数据来源: AIP

摘要:

Short‐tone thresholds were tested with an array of ten stimuli so chosen to incorporate a wide range of parameter variations. It was shown that the average data could be very well fitted with the function(I−I0)T = k, whereIis the stimulus intensity at threshold,I0andkare constants, whileTis the equivalent stimulus duration. This equivalent duration was derived for gradually rising and falling tone pips, and was shown to be computable asT = 2r/3+P, whereris the rise‐fall time andPis the peak time. It was shown that the above model predicted individual thresholds with considerably greater accuracy than other alternative descriptions. The theoretical implications of the model are the existence of a definite lower limit of stimulus intensity (I0), below which the stimulus power does not contribute toward threshold recognition, and the constancy of the effective utilizable energy at threshold (k). This latter quantity did not vary more than 0.5 dB from stimulus to stimulus.

ISSN:0001-4966    

DOI:10.1121/1.1919059

出版商:Acoustical Society of America    

年代:1964

数据来源: AIP

摘要:

Using binaural pitch‐matching data, the effect of moderate poststimulatory fatigue upon the ear's “tuning” was determined at several frequencies. In addition, the effect of the fatigue upon pitch discrimination was measured. Upward shifts in pitch were observed at TTS's of 20 dB at both 2800 and 5600 cps; however, the shift at 5600 cps is questionable since it was not statistically significant. From these data, Ruedi's observation that the direction of postfatigue pitch shifts reverses (decreases rather than increases) for frequencies above 4000 cps is questioned. There was limited evidence that fatigue results in poorer pitch discrimination; however, such effects were not marked. Possibly, monaural data would have resulted in more‐clearcut effects.

ISSN:0001-4966    

DOI:10.1121/1.1919061

出版商:Acoustical Society of America    

年代:1964

数据来源: AIP

摘要:

This experiment determined the pitch of mixed‐polarity pulse trains, high‐pass‐filtered at 2 and 4 kcps. It was found that pitch may be associated with pulse rate at rates higher than the limit of 150 pps found with unfiltered pulses. At frequencies higher than those supporting pulse‐rate pitch, some tendency to hear a pitch equal to the spectral difference frequency appears. Evidence for the difference‐frequency interpretation is the contrast in pitch of patterns equated for pulse number but possessing all‐harmonic and odd‐harmonic spectra. Comparison of the pitch results with a computer simulation of basiliar‐membrane displacements revealed some correlation of difference‐frequency pitch with displacement envelope. It is hypothesized that the high‐pass input‐filter slope combines with the natural‐membrane low‐pass characteristic to form a narrow passband. The envelope of membrane displacement at the passband site tends to contain a pitch‐significant frequency component equal to the difference frequency. It is furthermore suggested that a major source of the pitch of low‐frequency broad‐band periodic sounds is roughly the 400‐cps region of the basilar membrane.

ISSN:0001-4966    

DOI:10.1121/1.1919063

出版商:Acoustical Society of America    

年代:1964

数据来源: AIP

摘要:

Distribution curves for amplitude (envelope), drawn for noise and for noise plus signal, provide the basis for determining the proportion of area (probabilities) lying above various “criterion” levels. Probability pairsP(y|n) andP(y|sn) for various criterion levels furnish the coordinates of points generating ROC curves, which, because of the skewness of the distributions, show a slight curvature when plotted on normal‐normal paper. This curvature (concave downward) provides a better fit to detection data obtained from rating‐scale experiments than do the straight lines obtained from normal curves. The ROC curves belong to a family derived through the theory of signal detectability for the ideal observer in the case where signal phase is unspecified. The fact that the distribution for noise‐plus‐signal amplitudes has, in general, a larger variance than that for noise alone explains why many experiments find the ratio of σsnto σnto be greater than unity. A detection measured, derived from the two distribution curves, when plotted against signal amplitude, is a straight line over most of its course but bends in to the origin for weak signals. Its failure to touch the positive abscissa supports the TSD argument against the threshold hypothesis. A second curve, derived from this one, provides a convenient way of determining the signal required to yield a particular value ofds, when the signal that yields some other value ofdsis known. Finally, the concept of “effective bandwidth” is developed, and provides a single parameter for use in fitting detection data. Data give some support for the notion that the auditory system adjusts its bandwidth in accordance with the duration of the signal.

ISSN:0001-4966    

DOI:10.1121/1.1919064

出版商:Acoustical Society of America    

年代:1964

数据来源: AIP

摘要:

This paper considers the various techniques and equipment used in audiometer calibration. Sources of faulty performance in audiometers are pointed out and the methods of detection suggested. A complete laboratory calibration facility is described in some detail.

ISSN:0001-4966    

DOI:10.1121/1.1919066

出版商:Acoustical Society of America    

年代:1964

数据来源: AIP