摘要:

The pattern of hearing loss of children in schools for the deaf provides little information regarding etiology, but it is possible to evaluate the relative contribution of several etiologic factors by study of medical histories and family records. Traits such as thyroid or pigment anomalies can be used to identify particular genetic defects in a small proportion of deaf children; however, family data suggests that over half of all cases are the result of inheritance. Although most of the responsible genes are not now recognizable, pedigree data give excellent fit to simple genetic models. Thus we are able to estimate the minimum number of genes causing deafness and predict risks of deafness in offspring. Using experimental animals with patterns of hereditary deafness similar to man we can observe development and anatomy which suggest important directions for the study of deaf children.

ISSN:0001-4966    

DOI:10.1121/1.1913635

出版商:Acoustical Society of America    

年代:1973

数据来源: AIP

摘要:

Structural defects associated with deafness may be divided into two classes. The first class is associated with structures of the external and middle ear with the result that conduction of sound is impeded. Deformities of the external auditory canal and the ossicles may be hereditary and present at birth. Middle‐ear infections, otosclerosis, etc., acquired later may alter normal ossicular chain function. In the second class, the pathology is restricted to the internal ear. If the defect is congenital, it may have been inherited, or occurred “in utero” such as with rubella infections. After birth, an individual may be exposed to any number of situations which cause destruction of the hair cells and the cochlear nerve fibers. If the loss is extensive enough, a defective receptor organ results, with partial or complete deafness of the individual. It is not clear at present precisely what percentage of hair cells and nerve fibers are necessary for adequate social communication, but there is no replacement of degenerated receptor cells or sensory nerve fibers.

ISSN:0001-4966    

DOI:10.1121/1.1913636

出版商:Acoustical Society of America    

年代:1973

数据来源: AIP

摘要:

The merits and demerits of using a time‐discrimination technique to measure transmission loss through a wall are discussed. The method differs from those previously reported in that a wideband analogue approach is used throughout and the discrimination is improved by the use of a pre‐whitening filter before correlating.

ISSN:0001-4966    

DOI:10.1121/1.1913637

出版商:Acoustical Society of America    

年代:1973

数据来源: AIP

摘要:

The auditory threshold was measured for a pair of clicks in the presence of band‐rejected masking noise. This threshold depends on the interval between the two clicks. As the interval is changed, the threshold intensity alternately increases and decreases. For homopolar clicks and masking noise with a spectral gap centered atfHz, maxima are at (2n+1)/(2f) sec (n= 0,1,2,…). Experimental determinations of this fluctuation, for equal‐intensity clicks, are in quantitative agreement with predictions of a simple model. In the model, band‐stop noise produces a band pass filtering of the click stimulus, and the stimulus is detected if the long‐time average energy at the filter output exceeds some threshold value. However, if the clicks are of unequal intensity, the threshold is influenced by the click order. This order effect is inconsistent with the energy‐detection model.

ISSN:0001-4966    

DOI:10.1121/1.1913638

出版商:Acoustical Society of America    

年代:1973

数据来源: AIP

摘要:

The relationship between the parameters of pure‐tone acoustic stimuli and those of the cochlear microphonics (CM) and summating potentials (SP) was studied for measurements from scala media in each of the four turns of the guinea‐pig cochlea. For each turn similarities in the shapes of the input‐output functions over a wide range of frequencies permitted adequate quantitative description of these functions by a single third‐degree polynomial equation. Therefore, the properties of both cochlear potentials (CM and SP) can be described by a nonlinear transfer curve over the specified frequency range. These results imply the SP should not be regarded as being generated by a process different from the CM but as an expression of the nonlinear characteristics of the generator of cochlear potentials. At frequencies where the measuring electrode is near the peak of the mechanical traveling wave envelope, the transfer curve no longer described the cochlear potentials. Calculations based upon phase measurements and upon theoretical considerations indicate that this is due to interference effects from the out‐of‐phase generators in the vicinity of the electrode.

ISSN:0001-4966    

DOI:10.1121/1.1913639

出版商:Acoustical Society of America    

年代:1973

数据来源: AIP

摘要:

Models which attempt to account for our ability to discriminate the pitch of pure tones are discussed. It is concluded that models based on a place (spectral) analysis should be subject to a limitation of the type Δf⋅d⩾ constant, where Δfis the frequency difference limen (DL) for a tone pulse of durationd. The value of this constant will depend on the ability of the system to resolve small intensity differences. If a resolution of 1 dB is assumed, the value of the constant is about 0.24. In principle, a mechanism based on the measurement of time intervals could do considerably better than this. Frequency DLs were measured over a wide range of frequencies and durations. It was found that at short durations the product of Δfanddwas about one order of magnitude smaller than the minimum predicted from the place model, except for frequencies above 5 kHz. A “kink” in the obtained functions was also observed at about 5 kHz. It is concluded that the evidence is consistent with the operation of a time‐measuring mechanism for frequencies below 5 kHz, and with a spectral or place mechanism for frequencies above this.

ISSN:0001-4966    

DOI:10.1121/1.1913640

出版商:Acoustical Society of America    

年代:1973

数据来源: AIP

摘要:

A model for the generation and distribution of electrical potentials within the guinea pig cochlea was simulated by computer. Electrical impedances of the cochlear tissues and biological batteries in the stria vascularis and organ of Corti were modelled by a three‐dimensional network of resistors and batteries. It was assumed that cochlear‐partition movements caused electrical‐impedance changes in hair cells and resulted in modulation of steady‐state electrical currents normally flowing throughout the cochlea. The model response to a 1000‐Hz tone demonstrated that the amplitude envelope for the electrical current through the hair cells had the same shape as the mechanical traveling‐wave envelope, whereas the envelopes for the potential changes within cochlear scalae were broader and had their peaks nearer the basal end of the cochlea. Potentials generated by the model accurately reflected the amplitude and phase of the cochlear‐partition displacement only from the base to within about 3 mm of the peak of the traveling‐wave envelope. An important finding was that, when the impedance of a hair cell was decreased, current from adjacent hair cells was shunted through it, thus providing a possible excitation‐inhibition mechanism for neural sharpening.

ISSN:0001-4966    

DOI:10.1121/1.1913642

出版商:Acoustical Society of America    

年代:1973

数据来源: AIP

摘要:

A model based on Lighthill's theory for predicting aerodynamic noise from a turbulent shear flow is developed. This model is a generalization of the one developed by Ribner. It does not require that the turbulent correlations factor into space and time‐dependent parts. It replaces his assumption of isotropic turbulence by the more realistic one of axisymmetric turbulence. In the course of the analysis, a hierarchy of equations is developed wherein each succeeding equation involves more assumptions than the preceding equation but requires less experimental information for its use. The implications of the model for jet noise are discussed. It is shown that for the particular turbulence data considered anisotropy causes the high‐frequency self‐noise to be beamed downstream.

ISSN:0001-4966    

DOI:10.1121/1.1913643

出版商:Acoustical Society of America    

年代:1973

数据来源: AIP

摘要:

The current approach to noise survey work emphasizes the importance of spatial and temporal noise‐level variations, with less stress on frequency content. It is shown that a simple clock‐switched sound monitoring package,A‐weighted at the input stage, and with dynamic range of 45 dB, yields adequate information on which to base a concise, statistical model of the acoustic landscape. Because of the low‐cost nature of individual terminal units, a large number of units may be operated simultaneously over an extended area. This ensures that important spatial information is not lost. Such a detailed picture is not possible with the more conventional sequential (point to point) techniques which are normally employed.

ISSN:0001-4966    

DOI:10.1121/1.1913644

出版商:Acoustical Society of America    

年代:1973

数据来源: AIP

摘要:

This study investigated how well the file card system of “Voiceprint Identification” reported by Kersta fulfills its purpose of minimizing the effects of contextually caused spectral variation, and how well it serves as either an identification or population reduction tool. Subjects received training believed to be equivalent to that received by the experimenter in the Voiceprint Identification Training Course, and achieved error rates approximating those reported by Kersta for similar training tasks. Experimental tasks required subjects to identify unknown speakers from a population of 50 known speakers by first excluding all known speakers they were certain were not the unknown speaker, and then attempting absolute identification or elimination. Attempts were made under five experimental conditions created by combining two variables, phonetic context and inclusion of the unknown speaker in the known speaker population. The data show that the system tested does not effectively reduce the effects of contextual variation, and cannot be used for either absolute identification or elimination, or population reduction.The data suggest that the value of spectrograms for speaker identification purposes is limited to use as an investigative aid, and then only if speech samples of similar context and adequate duration are compared.

ISSN:0001-4966    

DOI:10.1121/1.1913645

出版商:Acoustical Society of America    

年代:1973

数据来源: AIP