摘要:

The acoustical damping system described in this paper uses a diaphragm, coupling chamber, and a resistive element in the form of a plug of porous sintered metal. A major feature of the development is the use of pressurization to match the acoustic impedance of the coupling chamber to that of the plug. Critical requirements which must be satisfied by the diaphragm, the chamber, the plug, and its acoustical termination are presented. The theoretical frequency response is presented in dimensionless form, and expressions for the dimensionless parameters are given in terms of physical constants of the instrument. Experience with instruments designed according to these principles and manufactured in quantity by Statham Instruments, Inc., has confirmed the theory.

ISSN:0001-4966    

DOI:10.1121/1.1907721

出版商:Acoustical Society of America    

年代:1959

数据来源: AIP

摘要:

The role of the volleys in the sensation of “pitch” on the skin was investigated. It was shown that the existence of rotating skin sensations does not insure perfect synchrony between sinusoidal vibrations and the discharges in the neural pathway. Experiments seem rather to indicate that, just as vibration loudness is a complex result of summation and inhibition, so is pitch sensation on the skin also influenced by summation and inhibition of a large group of end organs. One experiment showed that the pulse rate experienced on the skin is much lower than the pulse rate of the stimulus. This suggests a sort of “demultiplication” in the rate of the neural discharges along the neural pathway. This is one possible way in which synchronism may be maintained between the stimulus and the neural discharges, even though the frequencies transmitted are lowered.

ISSN:0001-4966    

DOI:10.1121/1.1907722

出版商:Acoustical Society of America    

年代:1959

数据来源: AIP

摘要:

Wires have been permanently implanted on the round window of the cochlea in cats. The voltage output of ears responding to sound stimulation has thus been made continuously available in unanesthetized animals for periods up to 4 months. By cutting the middle ear muscles of one ear and comparing its responses with those derived from the normal ear on the opposite side, it has been shown that the muscles: (1) do not appreciably influence absolute sensitivity, (2) contract to intense stimuli within 15 msec of their delivery to either ear, (3) attenuate transmission of tones between at least 500 and 3000 cps, and (4) significantly protect the ear against damage from intense sounds. Spontaneous contractions sporadically and intermittently introduce a transmission attenuation of several decibels in the resting normal cat. The stapedius muscle is much more important than the tensor tympani in producing these effects.

ISSN:0001-4966    

DOI:10.1121/1.1907723

出版商:Acoustical Society of America    

年代:1959

数据来源: AIP

摘要:

Electrical responses to low‐intensity repetitive clicks and bursts of noise were recorded from the cat auditory cortex. Responses decrease in size as the repetition rate is increased, and for rates higher than 50/sec are smaller than the “ongoing” activity of the cortex and become difficult to detect visually. An electronic average response computer was used to detect responses to high rates of stimulation. Stimulus‐locked responses to clicks and bursts of noise were found for rates up to 200/sec in unanesthetized cats, but only up to 100/sec after anesthetization.

ISSN:0001-4966    

DOI:10.1121/1.1907724

出版商:Acoustical Society of America    

年代:1959

数据来源: AIP

摘要:

The loudness of multitone complexes and bands of white noise was measured as a function of band width at levels between 5 and 35 db above threshold. When account is taken of the changes in the loudness that are due to the nonuniformity of the ear's sensitivity at low levels, the spreading of energy appears to have the same general effect on the loudness of both line spectra and continuous spectra centered at frequencies as low as 400 cps and as high as 5000 cps. At 5 db SL the spreading of energy does not increase the loudness, and may even decrease it. Above about 10 db SL, the spreading of energy in a complex sound over more than a critical band increases the loudness. As the sensation level is raised up to 35 db, the spreading of energy becomes more and more advantageous to loudness. The critical band defines the limits within which the spreading of energy leaves the loudness of a complex sound unchanged. The widths of the critical bands that were measured in these experiments on loudness summation below 35 db are approximately the same as those measured in experiments on loudness summation at higher levels and also in experiments on phase, threshold, and two‐tone masking.

ISSN:0001-4966    

DOI:10.1121/1.1907725

出版商:Acoustical Society of America    

年代:1959

数据来源: AIP