摘要:

It is commonly assumed that the two‐segmented input–output functions of the whole‐nerve action potential are a result of the activity of two sets of primary fibers: a low‐ and a high‐sensitivity group. While anatomical studies show the existence of two populations of fibers, there are no clear‐cut electrophysiological signs of two distinct populations responding with different thresholds. In light of this physiological result, it is desirable to construct a scheme for the growth of the whole‐nerve action potential that involves only one group of fibers. This can be done in a qualitative fashion by considering the pattern of single‐unit tuning curves and assessing the contribution of populations of units to the compound response. Thus the slowly growing low‐level segment of the input–output function is identified with the sharp tip region of the tuning curves of the responding units, while the high‐level, rapidly growing, segment is associated with the recruitment of higher‐frequency units that respond on the tail segment of their tuning curves. Thus the low and high parts of the input–output functions are interpreted in terms of the excitation of narrow and wide segments of the cochlear receptor. Masking experiments that support the scheme are described.Subject Classification: [43]65.35, [43]65.42, [43]65.59, [43]65.40.

ISSN:0001-4966    

DOI:10.1121/1.380818

出版商:Acoustical Society of America    

年代:1976

数据来源: AIP

摘要:

Multistate information was encoded within the temporal microstructure of multivariate auditory displays. Excellent discrimination of a two‐dimensional constraint between interpulse interval and pulse amplitude is achieved with 2 to 16 states per variable, but only if other display variables are fixed and the range of the controlled variables is relatively large. Under most of the conditions examined, discrimination of informational constraints within multivariate displays suffers as the number of encoded states is increased beyond two.Subject Classification :[43]65.75, [43]65.52, [43]65.22.

ISSN:0001-4966    

DOI:10.1121/1.380833

出版商:Acoustical Society of America    

年代:1976

数据来源: AIP

摘要:

Acoustic‐reflex thresholds were determined as a function of activating‐signal bandwidth in ten subjects with normal hearing sensitivity and eight subjects with noise‐induced sensorineural hearing loss. Results from the normal‐hearing group indicated that reflex thresholds decreased in a curvilinear fashion as a function of signal bandwidth in log frequency. Sensorineural hearing loss altered the functions by elevating reflex thresholds for signals in which the spectral content of the activating signal corresponded to the frequency region of the hearing loss. A method was proposed in which reflex thresholds for various tonal and bandlimited signals were used for predicting hearing sensitivity by frequency region.Subject Classification: [43]65.24, [43]65.22, [43]65.75.

ISSN:0001-4966    

DOI:10.1121/1.380834

出版商:Acoustical Society of America    

年代:1976

数据来源: AIP

摘要:

’’Effective quiet,’’ the highest SPL of a noise that will neither produce a significant temporary threshold shift (TTS) nor retard recovery from a TTS produced by a prior exposure to a higher level, is shown to be about 76 dB for octave bands of noise centered at 250 and 500 Hz, and around 68 dB for those centered at 1000, 2000, or 4000 Hz. On the other hand, a mean TTS2(TTS 2 min after exposure) of no greater than 10 dB at all frequencies from 500 to 5600 Hz is produced by a broad‐band noise whose octave‐band spectrum falls off at −5 dB per octave (’’magenta’’ noise) and which has anA‐weighted level of 90 dBA. When the group mean TTS2is 10 dB, less than 10% of normal ears will show a TTS2of 20 dB. Therefore if a 20‐dB TTS2is tolerable day after day with no adverse effects, the present industrial noise exposure limit of 8 h at 90 dBAwould adequately protect more than 90% of exposed workers in noises with similarly falling spectra. Correction factors for unusual spectra should, however, be developed.Subject Classification: [43]65.66, [43]65.64; [43]50.70.

ISSN:0001-4966    

DOI:10.1121/1.380835

出版商:Acoustical Society of America    

年代:1976

数据来源: AIP

摘要:

In masking period patterns, the SPL of a just‐audible triggered sequence of short high‐frequency test‐tone pulses varies as a function of their temporal spacing throughout the period of a low‐frequency masker. These patterns seem to be a psychocoustic equivalent of neurophysiologically measured period histograms. The duration of the test pulses resembles the bin‐width of the histograms. Optimal conditions for the measurement of masking period patterns were ascertained. The influence of the test signal parameters (duration, repetition rate, and frequency) was determined. Masking‐period patterns elicited by 50‐, 100‐ and 200‐Hz pure‐tone maskers of different levels are described and compared with corresponding neurophysiological data. The masking‐period patterns show similar periodic maxima and minima as physiological histograms, revealing the time structure of the stimulus. At high masker levels, the patterns seem to reflect nonlinear distortions. For masker frequencies higher than 100 Hz, the difference between maximum and minimum of the patterns decreases and drops to zero at about 500 Hz. This masker frequency corresponds to the psychoacoustically measured critical duration of about 2 msec, up to which the ear is able of resolving temporal fine structure. The correlation of masking‐period patterns with physiological data is discussed.Subject Classification: [43]65.58, [43]65.35, [43]65.75.

ISSN:0001-4966    

DOI:10.1121/1.380836

出版商:Acoustical Society of America    

年代:1976

数据来源: AIP

摘要:

The formant structure of three diphthongs, four tense vowels, and three retroflex sounds was examined in detail for possible speaker‐identifying features. These sounds were spoken five times each in sentence context by ten speakers of General American on one day and by six of the speakers on a second day at least three weeks later. Formant tracks were computed for each sound under investigation using covariance‐type pitch‐asynchronous linear prediction together with a root‐finding algorithm. The interspeaker variability of about 200 measurements made on these formant tracks was compared initially with intraspeaker variability through the calculation ofFratios. Those with averageFratios greater than 60 were evaluated further with a probability‐of‐error criterion. Features that are potentially most effective in identifying speakers are the minimum second‐formant value in [‐r], the maximum first‐formant value in [‐r], the maximum second‐formant values of [o] and [‐I], and the minimum third‐formant value of [‐]. The individual differences apparent in these sounds presumably depend more on speaker habits than on vocal‐tract anatomy. The error bound predicted for a speaker identification procedure based on these five features is 0.24%. An identification experiment using only the best two features gave 12 errors out of 80 identifications.Subject Classification: [43]70.65, [43]70.40.

ISSN:0001-4966    

DOI:10.1121/1.380837

出版商:Acoustical Society of America    

年代:1976

数据来源: AIP

摘要:

When CV targets are presented to one ear and isolated vowel masks to the other ear, the perception of the voicing feature of the target is biased by the temporal relationship between target and mask which acts like a ’’pseudo‐voice onset time’’ and competes with the actual voice onset time of the target as a voicing cue. The effect is especially strong when there is highaprioriuncertainty about the voicing category of the target, and it is more pronounced when the masking vowel lags behind than when it leads in time. The bias is strongest when the masking vowel is the same as the vowel of the target, but is present with a phonetically different vowel mask as well. There tends to be a right‐ear advantage which is strongest when the masking vowel leads in time. The fundamental frequency at masking vowel onset has an additional influence: The lower it is, the stronger is the tendency to identify the target as voiced. Two simple additive models of the vowel ’’masking’’ effect are rejected. The relative complexity of the effect suggests dichotic interaction at the phonetic (precategorical) level. The present experiments demonstrate that a temporal relationship, voice onset time, may be ’’masked’’ by another temporal relationship, the voice onset time across ears.Subject Classification: [43]70.30; [43]65.48, [43]65.58, [43]65.62.

ISSN:0001-4966    

DOI:10.1121/1.380838

出版商:Acoustical Society of America    

年代:1976

数据来源: AIP

摘要:

A linear approximation procedure has been applied to the derivation of shading coefficients for minor lobe control from symmetrical, but possibly irregularly shaped, transducer arrays, for which the relationship between the coefficients and output pressure is linear. Examples are included for the traditional problems of finding optimum coefficients for uniform and low minor lobe response from planar arrays, including one of a ’’honeycomb’’ array on a hexagonal grid, which could not be handled by analytical methods employed hitherto.Subject Classification: [43]85.40; [43]30.85; [43]20.55; [43]85.84.

ISSN:0001-4966    

DOI:10.1121/1.380839

出版商:Acoustical Society of America    

年代:1976

数据来源: AIP

摘要:

Recent investigations have utilized the measurement of the critical angle for reflection from a liquid‐solid interface for determination of the elastic constants of the solid. For anisotropic media, this technique is appropriate only for certain special cases of the incident plane and reflecting surface. We discuss here the general condition for the critical angel in anisotropic media and show that for some planes in quartz, major errors may arise if one employs the usual statement of Snell’s law for definition of the critical angle.Subject Classification: [43]20.30; [43]35.26.

ISSN:0001-4966    

DOI:10.1121/1.380847

出版商:Acoustical Society of America    

年代:1976

数据来源: AIP

摘要:

An additional calculation is made of diffraction of Rayleigh waves on homogeneous, isotropic elastic wedges following a formulation by Kane and Spence [Geophys. 28, 715–723 (Oct. 1963)]. For the wedges of which interior angles are close to 180°, power transmission, reflection and radiation coefficients can be derived in simple quadratic forms. Numerical data for rapid estimation of these coefficients are presented as functions of Poisson ratio.Subject Classification: [43]20.30; [43]35.54.

ISSN:0001-4966    

DOI:10.1121/1.380848

出版商:Acoustical Society of America    

年代:1976

数据来源: AIP