摘要:

Measurements are made of the relative effectiveness of the round window as a route of entrance of sounds to the cochlea. When the ear is normal this route is of no importance, but when the middle ear apparatus is absent and its advantage is lost to the oval window route a sound will have nearly equal access by both windows. When the inner ear is reached by both pathways at once the cochlear potentials represent the vector sum of what would result from the two separate waves. As phase and intensity relations between the two pathways are altered the potentials pass through maximum and minimum values, which for equal intensities of the two waves vary from a 6 db gain to a complete loss.Evidence is produced to show that each pathway of stimulation excites the same sensory cells and in the same intensity pattern.Over the major portion of the frequency range a minimum of response results when the waves are in phase as they enter the oval and round windows. Departures from this relation, which are most prominent at the highest frequencies, are explained as the result of reactance differences between the two windows.These results apply to the explanation of forms of deafness caused by interruption of the ossicular chain, and also to the explanation of the treatment of otosclerosis by means of the fenestration operation.

ISSN:0001-4966    

DOI:10.1121/1.1906628

出版商:Acoustical Society of America    

年代:1950

数据来源: AIP

摘要:

The report describes measurements of the frequency limits of binaural beats and outlines a theory of binaural beats, based on synchronous discharges in the two auditory nerves. Two sinusoids of frequenciesf1(fixed) andf2(variable) were led separately to the two ears; and the differenceΔf = |f1−f2|that marked the disappearance of the fluctuating loudness or roughness that is characteristic of binaural beats was determined. Δfwas maximal (approximately 35 c.p.s.) for frequencies in the neighborhood of 400 c.p.s. Binaural beats were heard above 1000 c.p.s., but careful attention was required and Δfwas small. The shape of the curve relating Δftof1provides an explanation for the fact that determinations of the upper frequency limit of binaural beats have not been in agreement; the upper frequency limit depends markedly on Δf. The theory, given to account for the fact that Δfis smaller both at low and at high frequencies than it is near 400 c.p.s., combines elements of the Hill‐Rashevsky theory of the excitation of neurons with elements of Wever's volley theory. At low frequencies neurons can discharge in some degree of synchrony with the stimulus wave form, yet fail to coincide within the time interval necessary for synaptic summation. At high frequencies the neurons must take turns discharging, and relatively few can participate in any given volley. At intermediate frequencies, however, each neuron participates in many volleys and the neurons participating in each volley fire almost simultaneously. The result is that at intermediate frequencies synchrony is relatively precise in each afferent pathway and, when the two afferent streams join in a common neural center, beats appear.

ISSN:0001-4966    

DOI:10.1121/1.1906629

出版商:Acoustical Society of America    

年代:1950

数据来源: AIP

摘要:

A phonographically recorded test of the ability to hear pure tones was given to 3666 people at the San Diego County Fair in the summer of 1948. Absolute thresholds were determined at five frequencies and masked thresholds at two frequencies. The results were analyzed according to the age, sex, musical training, and past noise environment of the listeners, and according to their statements as to whether or not they had difficulty in hearing. As expected, auditory sensitivity was found to decline with age; women were found to be more sensitive than men for the higher frequencies; and men who worked in noise showed greater than normal losses at high frequencies. The data indicated, in addition, that musically trained men and women possess greater hearing sensitivity than do men and women without musical training, and that the 20–29 year old males tested at San Diego in 1948 appeared to have a greater loss at the high frequencies than did most males of the same age group who were tested in surveys before the war.

ISSN:0001-4966    

DOI:10.1121/1.1906630

出版商:Acoustical Society of America    

年代:1950

数据来源: AIP

摘要:

Absolute thresholds and thresholds of pure tones masked by thermal noise were obtained for 3666 persons attending the 1948 San Diego County Fair. The masked hearing losses as well as the absolute hearing losses (1) increased with an individual's age, (2) were positively correlated with his awareness of hearing difficulty, and (3) were inversely related to his musical training. Masked losses, however, were less dependent upon one's sex and upon one's past noise environment than were absolute losses.When groups of individuals were equated as to their absolute losses on 880 c.p.s. and 3520 c.p.s. (the frequencies which were masked), that part of each group that had the lower absolute thresholds on 440 c.p.s. also had the lower masked thresholds.The signal to noise ratio (noise expressed as spectrum level) at masked threshold for those with no absolute loss was 20 db at 880 c.p.s. and 21 db at 3520 c.p.s. This is equivalent to saying that the noise bands which were effective in masking these frequencies were 100 and 128 cycles wide, respectively.

ISSN:0001-4966    

DOI:10.1121/1.1906631

出版商:Acoustical Society of America    

年代:1950

数据来源: AIP

摘要:

The results of experiments on masking of tones by narrow bands of noise at 200, 800, and 3200 c.p.s. are presented. These are interpreted in terms of the critical band hypothesis. Assuming a simple resonant characteristic for the aural frequency selectivity the shape of the maskingvs.frequency function is computed and gives a reasonably good fit in the narrow regions studied. The critical band widths are determined at frequencies 200, 800, and 3200 c.p.s., and the corresponding values ofQof the equivalent tuned circuit are given. Data are presented for masking of tones slightly removed from the masking noise band, and are shown in fair agreement with the computed values. The selectivity curves are shown to be consistent with available data on differential sensitivity to frequency.

ISSN:0001-4966    

DOI:10.1121/1.1906632

出版商:Acoustical Society of America    

年代:1950

数据来源: AIP

摘要:

When a pure tone and a masking noise are fed into the same ear simultaneously, the pitch of the pure tone is raised. The effect is more pronounced at low loudness levels and is progressively greater as the frequency of the tone rises. Apparently the phenomenon is not present if the pure tone is 20 db or more above its masked threshold. Nineteen graduate music students served as subjects in the experiment. Control measurements were made to estimate the effects of diplacusis and of the difference in intensity between the masked and the unmasked pure tone when they were matched in loudness.

ISSN:0001-4966    

DOI:10.1121/1.1906633

出版商:Acoustical Society of America    

年代:1950

数据来源: AIP

摘要:

The magnetostrictive properties of Hiperco, a magnetic alloy of iron, cobalt, and chromium, were investigated to determine its suitability as a material for electromechanical transducers. The relations between the magnetic and magnetostrictive characteristics of a material and its performance as a transducer element are reviewed and criteria for its evaluation established. The properties of Hiperco, measured after a suitable heat treatment had been determined, are discussed in relation to these criteria and a comparison made with nickel and Permendur. For operation at magnetic remanence Hiperco is shown to be as good as Permendur for hydrophone applications, but inferior to nickel and Permendur when used as an underwater projector at high power levels. When polarized above remanence maximum value of 0.17 for the electromechanical coupling coefficient is realized and operation as a projector is improved. Performance data are given for a small underwater transducer constructed of Hiperco operating at remanence.

ISSN:0001-4966    

DOI:10.1121/1.1906634

出版商:Acoustical Society of America    

年代:1950

数据来源: AIP

摘要:

Studies of the response of an auditorium to a short tone burst have indicated that the character of the first 20 or 30 db of sound decay, the “short‐term” response, is closely related to the subjective “hearing quality” of the room. Recently Haas has investigated the effect of a single echo on the subjective hearing of speech. On the basis of some of Haas' results and other information on the hearing of speech in rooms, a tentative criterion for the short‐term response has been formulated as curves of amplitudevs.time delay of each reflection relative to the direct sound. The criterion correctly rank‐orders subjective quality observations reported by others, and agrees quantitatively with some subjective judgments reported here.

ISSN:0001-4966    

DOI:10.1121/1.1906635

出版商:Acoustical Society of America    

年代:1950

数据来源: AIP

ISSN:0001-4966    

DOI:10.1121/1.1906636

出版商:Acoustical Society of America    

年代:1950

数据来源: AIP

ISSN:0001-4966    

DOI:10.1121/1.1906637

出版商:Acoustical Society of America    

年代:1950

数据来源: AIP