摘要:

In order to compare the temporary threshold shift (TTS) produced by bands of thermal noise with that produced by pure tones, eight ears (four subjects) were exposed to pure tones of 500 and 3200 cps, and to noise bands 5 cps, one‐third octave, and one octave wide, centered at these same frequencies. The exposures were at a sound‐pressure level of 110 db. After exposure, the subject tracked his 4000 cps threshold for 3 min and then his 500, 1000, 2000, 4000, and 6000 cps thresholds for the next 12 min on a Békésy type audiometer. The threshold shifts at these frequencies were found to be essentially the same regardless of the exposure stimulus type. The threshold shifts from exposures in the 500 cps region were very small, but the “bounce” phenomenon was particularly prominent.

ISSN:0001-4966    

DOI:10.1121/1.1908509

出版商:Acoustical Society of America    

年代:1961

数据来源: AIP

摘要:

Using essentially the methods of Lyon and Dyer the response of a one‐dimensional, simply supported elastic system (such as a string or a bar) to random convecting force fields is calculated. The spatial as well as the time dependence of the correlation function of the force field are assumed to decay exponentially. The response is analyzed as a function of the force‐field parameters in relation to the dynamic characteristics of the system. Special attention is focused on the limiting case where the correlation function approaches the delta‐function form in space or time or both. In this way a criterion is established for the validity of the delta function approximation for such problems.

ISSN:0001-4966    

DOI:10.1121/1.1908511

出版商:Acoustical Society of America    

年代:1961

数据来源: AIP

摘要:

A re‐examination of Lyon's experimental results on turbulent excitation of strings is made in the light of new information on boundary‐layer turbulence and on extended theoretical calculation. It is shown that the extended theory together with reasonable modifications in the parameters describing the turbulent flow leads to better agreement between experiment and theory.

ISSN:0001-4966    

DOI:10.1121/1.1908513

出版商:Acoustical Society of America    

年代:1961

数据来源: AIP

摘要:

Many new improvements over earlier models of the phonetic typewriter have resulted from developments which provide means for reducing the number of different displays obtained for the same syllable without unduly increasing the complexity of the machine. In terms of the ultimate machine which should provide means for handling 1000 to 2000 syllables, model III with a maximum capacity of about 100 syllables is still a rudimentary phonetic typewriter. However, the model III provides a complete system from the sounds of speech input to the typed‐page output which is of great value in future research in speech analysis. Specifically, the subjects considered in this paper are as follows: form of the typed presentation, construction, circuits, syllable memory, typing console, spelling memory, choice of vocabulary, procedure for setting up the memory, and codes obtained.

ISSN:0001-4966    

DOI:10.1121/1.1908515

出版商:Acoustical Society of America    

年代:1961

数据来源: AIP

摘要:

A transformation has been derived relating the number of spheres of a certain radiusRper unit volume (the “volume distribution of spheres”) to the number of circles smaller than a certain radiusrper unit area (the “area distribution of circles”) appearing on a plane cutting through the volume. The transformation was applied to several hypothetical grain‐size distributions for polycrystalline metals to find the resulting hypothetical area distribution of grain images on photomicrographs. Comparison of the hypothetical area distributions to experimentally found area distributions gave the following conditions that the true volume distribution of grains must meet: (1) It must be finite atR=0, and (2) it must have a nonzero decreasing tail for large values ofR. The common assumption of a single grain diameter is insufficient to explain the experimental area distribution of grain images. The functionsNV(R) = Rn exp(−kR)andNV(R) = exp[−(lnR/R0)2/2σV2]were judged plausible for the volume distribution function of grains, and a correction was computed for the attenuation formulas for Rayleigh scattering of ultrasonic waves in polycrystalline metals by taking averages ofR6andR3over these functions.

ISSN:0001-4966    

DOI:10.1121/1.1908517

出版商:Acoustical Society of America    

年代:1961

数据来源: AIP

摘要:

In the first part of this work the double refraction observed while measuring the attenuation of ultrasonic transverse waves in heat‐treated 4150 steel was investigated. Although the data are not complete, they suggest that this double refraction phenomenon can be utilized to detect the amount of preferred orientation of the crystallites in rolled steel when this orientation is small. Calculated values of fractional velocity differences are given.In the second part the theory of ultrasonic wave propagation in polycrystalline metal is discussed, and the effect of preferential orientation of crystallites on fractional velocity changes is indicated. The use of ultrasonic double refraction data for determining the extent of preferential orientation is discussed.

ISSN:0001-4966    

DOI:10.1121/1.1908519

出版商:Acoustical Society of America    

年代:1961

数据来源: AIP

摘要:

A new table of frequencies is suggested to American Standards Association as amendment to S1. 6‐1960.

ISSN:0001-4966    

DOI:10.1121/1.1908521

出版商:Acoustical Society of America    

年代:1961

数据来源: AIP

摘要:

A resonance‐tube method has been developed for the measurement of sound absorption and velocity in gases at frequency to pressure ratios from 36 to 3800 cps atm. Measurements in oxygen at 30°C show velocity dispersion and excess absorption due to relaxation of the vibrational mode of the oxygen molecule with a relaxation time of 3.2±0.3 × 10−3sec. The results are in agreement with those obtained by Knotzel and Knotzel.

ISSN:0001-4966    

DOI:10.1121/1.1908525

出版商:Acoustical Society of America    

年代:1961

数据来源: AIP

摘要:

The frequency of the edge mode, which is closely associated with the complex branches of the dispersion equation, has been approximated by taking only the complex branches into account.The frequencies for a thin rectangular plate, a circular disk and a rod have been evaluated as functions of Poisson's ratio and compared with the observed values by various investigators.

ISSN:0001-4966    

DOI:10.1121/1.1908527

出版商:Acoustical Society of America    

年代:1961

数据来源: AIP

摘要:

The frequency spectrum of a thin rectangular plate of barium titanate ceramics has been measured as a function of length/width ratio with a particular emphasis on a special mode of contour vibration, named edge mode.

ISSN:0001-4966    

DOI:10.1121/1.1908529

出版商:Acoustical Society of America    

年代:1961

数据来源: AIP