摘要:

This paper describes a moving coil microphone, one of the principal features of which is its nondirectional characteristic, that is, its ability to pick up with equal fidelity sound coming from all directions. This nondirectional property is attained largely by the use of an acoustic screen which is located in front of the diaphragm of the microphone. In addition, this microphone possesses the advantages of small size, light weight, and a uniform response over a wide range of frequencies.

ISSN:0001-4966    

DOI:10.1121/1.1915822

出版商:Acoustical Society of America    

年代:1936

数据来源: AIP

摘要:

The electrical potentials generated in the cochleas of guinea pigs were picked up by electrodes in contact with the bone or external membranes of the cochlea and the neck muscles. These potentials were studied as a function of the position of the electrodes and the condition of the organ of Corti within the cochlea in order to determine the specificity of resonance of the basilar membrane to tones of various frequencies, and thereby discover the role of the cochlea in pitch perception.Audiograms of the electrical response were taken before and after drilling through the cochlear wall and damaging the organ of Corti at various points. The exact location and extent of each lesion were determined by subsequent microscopic study of serial sections of the cochleas and these were correlated with the losses in hearing revealed by the audiograms. Good correlations were obtained in 20 animals between the boundaries of lesions and sharp departures of the audiograms from normal.The positions of the resonant areas for tones of various frequencies indicated by these results are confirmed by the locations derived from an integration of the most recent data for differential sensitivity to pitch in human ears. High tones are localized near the basal end of the cochlea, 2000 c.p.s. is at the middle, and the lower octaves are closely bunched toward the helicotrema.

ISSN:0001-4966    

DOI:10.1121/1.1915826

出版商:Acoustical Society of America    

年代:1936

数据来源: AIP

摘要:

Functional relationships obtained from studies of the electrophysiology of the auditory mechanism in animals may be used to determine the physical basis of the psychological aspects of hearing. Thus equal magnitudes of electrical potential are generated by the hair‐cells of the inner ear when subjected to tones (of different frequency and intensity) which sound equally loud to the human observer, i.e., equal potential contours correspond to equal loudness contours. Therefore, loudness appears to be proportional to cochlear potential. Since end‐organ stimulation can reach the brain only via afferent nerves which conduct series of discrete action potentials, loudness must also depend upon the number of fibers involved in the transmission of a volley of action potentials.The relation of the size of the cochlear potential to the intensity of sound deviates from the Weber‐Fechner relationship in the same manner as do the psychological functions. However, at about 60–80 db above threshold the cochlear potential begins to decrease, and a reversible depression of the response, due to overload, is shown by a “hysteresis” effect. If the overload is prolonged, microscopic degeneration of the hair‐cells occurs, or if overload is too great the organ of Corti is shaken loose from the basilar membrane.For a given tone the potential recorded from the scala vestibuli is out of phase by 180° with that recorded from the scala tympani. Therefore the potential drop is across the membrane, or from end to end of the hair‐cells. The potential at the round window is in phase with that in the scala tympani, but the potential at the apex differs from the potential in the scala vestibuli by an angle which increases with the frequency of the stimulus. By moving the grid electrode along the outside of the cochlea, a point is found where the potentials which leak out of the two ends (round window and apex) cancel each other by interference.

ISSN:0001-4966    

DOI:10.1121/1.1915827

出版商:Acoustical Society of America    

年代:1936

数据来源: AIP

摘要:

In studying the effects produced by two or more source simultaneously emitting the same sounds, it has frequently been noticed that all of the sound appears to come from the nearest source provided the difference in distances between the observer and the sources lies between fairly definite limits. A group address system was set up to utilize this effect in making it appear to the audience that the amplified sound of the speaker's voice came directly from his mouth. Excellent results were obtained, even with relatively great amplification, when the sound reproducing units were about 20 feet behind and 45 feet above the speaker.

ISSN:0001-4966    

DOI:10.1121/1.1915831

出版商:Acoustical Society of America    

年代:1936

数据来源: AIP