摘要:

Some exploratory studies of temporary threshold shifts (TTS) induced by acoustic pulses are described. Attempts to determine the effect of pulse rate on TTS were only partially successful because at rates of 1 click/sec or more, residual activity of the protective reflex produced by one click reduced the effective intensity of the next click. The protection induced by this reflex was next examined by using, TTS from clicks as the dependent variable; a tone of 1000 cps at 103 db SPL, presented to the contralateral ear 105 msec before the click, reduced its effective intensity by about 10 db. The TTS at 4 kc was shown to increase linearly with exposure time; that is, the TTS from pulses is proportional to the number of pulses presented. The average TTS produced by pulses has a broad maximum at 4 kc, but this maximum may vary from 2 to 10 kc for different observers. Striking individual differences were observed throughout the experiments. Certain aspects of the distinction of pitch that is often correlated with large values of TTS are described.

ISSN:0001-4966    

DOI:10.1121/1.1908799

出版商:Acoustical Society of America    

年代:1961

数据来源: AIP

摘要:

A mechanical model of the middle ear is obtained from anatomical observations. The differential equations for the model are solved, and the solutions are found in good agreement with the impedance of the ear at the tympanic membrane measured in many earn of fresh cadavers. Thus, the mechanism of the middle ear is clarified theoretically as well as experimentally. The ossicular chain loaded with the impedance of the cochlea is found to be the most important factor controlling the impedance of the tympanic membrane. The ossicular chain has two resonances: the lower one due to the malleoincudal body, and the higher due to the stapes. Thus, the ossicular chain keeps the reactance of the tympanic membrane near or at its resonances. The function of the air cavities behind the tympanic membrane is found to be similar to but less than that of the ossicular chain. The apparent pressure gain by the middle ear for the cochlea is measured. From these data the frequency characteristic of the ossicular chain the impedance of the stapes are calculated. Moreover, it is found experimentally as well as theoretically that the transmission of the middle ear is not only increased by a lower impedance of the tympanic membrane but also by a higher impedance; transmission is increased by the tympanic membrane vibrating as a rigid cone attached to the ossicular chain even though such attachment increases the impedance of the tympanic membrane.

ISSN:0001-4966    

DOI:10.1121/1.1908801

出版商:Acoustical Society of America    

年代:1961

数据来源: AIP

摘要:

The vibrations of an artificially blown clarinet were studied by a photoelectric method in which light from a source placed at the bell of the instrument passed through the aperture between the reed and the mouthpiece and into a photomultiplier tube whose output was observed on an oscilloscope. It was found that for loud tones the aperture is practically completely closed for about one‐half cycle and completely open for the other half. For softer tones the aperture does not close completely and the reed motion becomes nearly sinusoidal. A small condenser microphone inserted in the clarinet mouthpiece allowed simultaneous observations of the reed vibrations and air column vibrations to be made. It was found that during that part of its motion that the reed is not in contact with the mouthpiece it follows quitef aithfully the variations in mouthpiece air pressure. The sound pressure level in the mouthpiece reaches 166 db for loud tones; this value checks well with the pressure required for blowing the instrument. The increased loudness of the clarinet on harder blowing is due primarily to the increased production of harmonics.

ISSN:0001-4966    

DOI:10.1121/1.1908803

出版商:Acoustical Society of America    

年代:1961

数据来源: AIP

ISSN:0001-4966    

DOI:10.1121/1.1908807

出版商:Acoustical Society of America    

年代:1961

数据来源: AIP

摘要:

The reflection of sound from a grating is discussed in the case when the slit width of the grating is small compared to half a wavelength of the incident sound. Then only the specular reflection will be present. The corresponding reflection coefficient is determined as a function of the angle of incidence of the sound and the results are applied to study the influence of a floor grating on the acoustic performance of an anechoic room.

ISSN:0001-4966    

DOI:10.1121/1.1908811

出版商:Acoustical Society of America    

年代:1961

数据来源: AIP

ISSN:0001-4966    

DOI:10.1121/1.1908815

出版商:Acoustical Society of America    

年代:1961

数据来源: AIP

摘要:

The shape of curves for peak density of response of hard‐spring resonators depends significantly on the choice of variable and the choice of normalization constant (the rms value of some variable). The curves for the variables: (1) displacement (bending strain in pinned bar) normalized to linear expectation of rms, (2) displacement normalized to actual rms, and (3) total strain (bending plus membrane, in pinned bar) normalized to linear expectation of rms—are compared with the linear case. Comments are made on the problems of comparing experimental data with these curves.

ISSN:0001-4966    

DOI:10.1121/1.1908818

出版商:Acoustical Society of America    

年代:1961

数据来源: AIP

摘要:

The effect of membrane strain on thee fatigue damage rate of a bar with simply supported ends is calculated based on asymptotic expressions for the extremal moments of a hard‐spring oscillator. The calculations are appropriate for a high degree of nonlinearity. Comparisons with numerical calculations are satisfactory.

ISSN:0001-4966    

DOI:10.1121/1.1908820

出版商:Acoustical Society of America    

年代:1961

数据来源: AIP

摘要:

A quick and simple method of determining the effect of temperature change on the response of an underwater sound transducer is described. The method requires precooling or warming the transducer to the extreme temperature of interest and then monitoring its response while its temperature returns to ambient.

ISSN:0001-4966    

DOI:10.1121/1.1908822

出版商:Acoustical Society of America    

年代:1961

数据来源: AIP

ISSN:0001-4966    

DOI:10.1121/1.1908825

出版商:Acoustical Society of America    

年代:1961

数据来源: AIP