摘要:

This investigation studies the effect of humming and of certain nonvocal activities on TTS (temporary threshold shifts) from a 5‐min 500‐Hz 118‐dB SPL exposure. The experimental technique consisted of measuring hearing thresholds at 700 Hz before and after exposure, this exposure being accompanied by the performance of a specific activity such as humming. Analysis of the results indicates that TTS from the exposure accompanied by humming was significantly less than TTS from exposure without any supplementary activity. The following conditions were tested: (1) humming at 125 Hz (males) or 250 Hz (females); (2) humming loudly at the same frequencies; (3) humming at 250 Hz (males) or 500 Hz (females). TTS in cases (2) and (3) was consistently less than TTS in case (1). Repeatedly turning the head during exposure, an activity believed to elicit middle‐ear muscle contraction, resulted in less TTS than no activity during exposure. Listening to recorded humming during exposure did not significantly alter TTS from the exposure, nor did the activity of exhaling after preparing to hum. Attenuation provided by middle‐ear muscle contraction during phonation does not appear sufficient to decrease TTS to the extent that humming does. Sound may be attenuated by inefficient stapes vibration during phonation and TTS may thus be reduced. Two other possibilities are discussed that could account for the TTS decrease: interference between humming and the exposure tone; and interference (by humming) with the central control of middle‐ear muscle activity.

ISSN:0001-4966    

DOI:10.1121/1.1913221

出版商:Acoustical Society of America    

年代:1972

数据来源: AIP

摘要:

Carder and Miller [Trans. Amer. Acad. Ophthalmol. Otolaryngol.75, 1346–1354 (1972)] exposed chinchillas for seven days to an octave band of noise centered at 500 Hz and at 95 dB SPL to produce temporary shifts of behavioral auditory thresholds (TTS) of about 48 dB which required four to seven days to recover to normal. In the present study physiological potentials were measured about 5, 24, and 48 h after exposures to the same noise for two or three days. Cochlear microphonic (CM) responses and dc endocochlear potentials were measured in each of the three cochlear turns. Input‐output functions for whole‐nerve action potential (AP) responses to clicks and visual detection levels (VDL) for early averaged evoked responses (AER) arising in the brain stem were also measured. Endocochlear potentials were unchanged. Shifts of sensitivity for CM in the second and third turns showed the closest numerical correspondence to behavioral TTS. Loss of sensitivity for AP was greater. Changes in VDL for the AER were consistent with behavioral TTS. This pattern of physiological changes was consistent with a disorder in the mechano‐electric modulation by the hair cells plus failure to synchronize primary neural responses. Just‐detectable loss of outer hair cells was also observed anatomically.

ISSN:0001-4966    

DOI:10.1121/1.1913222

出版商:Acoustical Society of America    

年代:1972

数据来源: AIP

摘要:

Estimation of aural harmonic magnitudes with the tone‐on‐tone masking paradigm requires calculation of the monaural phase amplitude effect from measurements of threshold level tones. Such amplitudes have been approximated with a sinusoid but may be more precisely determined by fitting the data with the circle,Ar2 = Ae2+A12−2AeA1 cos(ψ). An algorithm for this procedure is detailed.

ISSN:0001-4966    

DOI:10.1121/1.1913223

出版商:Acoustical Society of America    

年代:1972

数据来源: AIP

摘要:

The apparent loudness of a tone pip can be increased by 15 dB or more if it is preceded by a tone burst to the contralateral ear. The experiment is done by delaying the pip, S1, by a variable time, ΔT, after the offset of a contralateral tone; the listener assesses the loudness of S1by adjusting the intensity of a second tone pip, S2, that follows S1by 1500 msec. Some parametric explorations of the phenomenon are reported here.

ISSN:0001-4966    

DOI:10.1121/1.1913224

出版商:Acoustical Society of America    

年代:1972

数据来源: AIP

摘要:

The envelope of the rms deflection of the basilar membrane has been studied by means of a digital computer model simulation. The deflection envelope was observed for equal‐intensity bandlimited noise stimuli centered at a frequency of 300 Hz. Two kinds of noise‐band symmetry were used: arithmetic and geometric. Bandwidth was varied in steps from pure tone to 4 oct. It was found that as the bandwidth of the noise increased, the length of the membrane that exceeded an arbitrary threshold increased quite slowly until a bandwidth of about 100 Hz was reached. The threshold used was 0.5 of the maximum deflection to pure tone. At higher bandwidths, suprathreshold membrane length increased more markedly. When a higher threshold near that of the pure‐tone maximum deflection was employed, the suprathreshold membrane length decreased then increased with bandwidth. Comparison of these results with psychoacoustic studies on loudness and the critical band reveal similarities. They suggest that loudness phenomena may originate peripherally and be associated closely with the extent of the basilar membrane simulated.

ISSN:0001-4966    

DOI:10.1121/1.1913225

出版商:Acoustical Society of America    

年代:1972

数据来源: AIP

摘要:

Combination bandsgenerated by a pure tone and a narrow band of noise are detected and produce masking patterns in the frequency region below the primaries (Greenwood, 1969a, 1969b, 1970, 1971a, 1971b). Virtually identical masking patterns are produced by noise bands of external origin, situated on the low‐frequency side of a more intense tone. Patterns in both cases take the form of elevations that merge with, or stand in isolation from, thelow‐frequency side of the masked audiogram produced by the tone, depending on the separation of the band from the tone. This study of masking by bands of external origin was undertaken (a) to measure the effect, if any, of the higher‐frequency more intense tone on masking exerted by the noise of known intensity; (b) to permit, thusly, inferences to be made as to the effects of a lower primary on the masking exerted by acombination bandbelow it; (c) to obtain signal/masker ratios for use in estimating combination band levels; and (d) to study one experimental situation bearing on the “additivity of masking” problem. Conclusions pertaining to these objectives are, respectively: (a) that the presentation of a higher‐frequency more intense tone with a band of noise does not increase the masking maximum produced by the noise; (b) that it is plausible to assume that masking by combination bands is not affected by the lower primary above it; (c) that the obtained signal/masker ratios can be used to estimate combination band levels; and (d) that, although the tone does not increase masking by the noise, weaker lower‐frequency noise can affect masking by the tone.

ISSN:0001-4966    

DOI:10.1121/1.1913226

出版商:Acoustical Society of America    

年代:1972

数据来源: AIP

摘要:

In a previous paper (Greenwood, 1972a), the measurement of masking by bands of noise of external origin led to determinations of signal/masker ratio that are applied in the present paper to the task of estimating combination band levels. Estimates of the levels of combination bands, given by the expression(n + 1)fl − nfh, were made by using the maximum masked threshold, read from a masking pattern produced by a given band, to calculate the denominator of the previously obtained signal‐to‐masker ratio. The shapes of the masking patterns and the estimates of level lead to the following conclusions: (a) Comparison of the masking effects of combination bands and bands of external origin further demonstrates that to assume that combination components, once generated, arenotequivalent to external stimuli in ultimate loci and subsequent effects in the cochlea would require complexad hocexplanations to account for the indistinguishable masking effects produced by the two kinds of bands. (b) Combination bands generated by mixtures of line and continuous spectra vary in level as functions of stimulus parameters in ways very similar to the variation in the level of combination tones produced by tonal primaries, as measured by cancellation techniques (Zwicker, 1955, 1968; Goldstein, 1967). (c) The present data extend the previously reported empirical functional relations, in that the level of the band2fl>−fhis (i) a less sensitive function of primary frequency separation at higher primary levels and (ii) a more nearly constant percentage of primary level at wider primary separations. (d) The generation of combination components in essentially the same way, whether they are produced by line, continuous, or mixed spectra, should advance the task of calculating empirically the amplitude characteristics of the combination spectra produced by complex primary spectra.

ISSN:0001-4966    

DOI:10.1121/1.1913227

出版商:Acoustical Society of America    

年代:1972

数据来源: AIP

摘要:

The levels of the difference bands,fh − fland2(fh − fl), generated by a pure tone and a narrow band of noise, have been estimated in a manner reported in previous papers (Greenwood, 1971a, 1972a, 1972b). Results and conclusions follow: (a) Combination bands of the formfh − fland2(fh − fl)vary in level as functions of stimulus parameters in ways very similar to the variation in level of the differencetone,fh − fl, produced bytonalprimaries, as measured by cancellation techniques. Difference band levels are rather insensitive to increases of primary frequency ratio in the ranges explored (about 1.35–1.85). Difference band level obeys different functions of primaryintensitydepending on whether one or two, and whether the upper or the lower, primaries are varied. When the lower primary level is varied alone, square‐law behavior is observed, in agreement with Goldstein (1967) and with Zwicker (1955); when the upper primary or both primaries vary, curves depart from square‐law behavior in near agreement with Goldstein. Békésy's 1934 observations (1960) and Wenner's (1968) results suggest a conceivable explanation that might resolve some apparent discrepancies among results of Goldstein, Zwicker, and this paper whenbothprimaries vary. (b) At primary levels exceeding about 60 dB SPL, combination tones of the formn(fh − fl)and combination tones of the form(n + 1)fl − fhwill exist simultaneously, and since they lie in the same frequency region they will interchange places, with varying interactions, as primary ratios are varied—producing perceptual effects relevant to higher‐level phenomena of consonance generally and to the beats of mistuned consonance specifically.

ISSN:0001-4966    

DOI:10.1121/1.1913228

出版商:Acoustical Society of America    

年代:1972

数据来源: AIP

摘要:

The contralateral acoustic reflex, elicited by wide‐band noise and pure tones whose frequencies ranged from 200–2000 Hz, was measured and studied by using dynamic recordings of the change of the input acoustic impedance of the eardrum. Step and sinusoidal (envelope) stimuli with the above carriers at different sound pressure levels (SPLs) were used, and four human subjects with normal hearing were tested. It was shown that the dynamic properties of the acoustic reflex are both frequency‐ and magnitude‐dependent. In general, within the dynamic range of the reflex, the speed of on‐response (with step input) seemed to be proportional to the SPL of the stimulus. This proportionality was more clearly observed in the on‐response of the reflex elicited by stimuli having pure tone carriers than wide‐band noise carriers. The sinusoidal responses of the reflex tended to indicate that the apparent bandwidth of the reflex mechanism increases with SPL. The most distinct frequency‐dependent characteristic of the reflex was observed in the on‐responses of the reflex with different carriers, namely an underdamped oscillatory response was seen when the carrier frequency fell between 400–800‐Hz range and an overdamped on‐response outside this range. It was suggested that the magnitude dependence of the reflex could be attributed to a magnitude‐dependent nonlinearity of the muscle mechanism, while the frequency‐dependent characteristic was due to frequency‐dependent attenuation of the sound transmission due to the activity of the acoustic reflex.

ISSN:0001-4966    

DOI:10.1121/1.1913229

出版商:Acoustical Society of America    

年代:1972

数据来源: AIP

摘要:

Twelve squirrel monkeys were exposed to pure‐tone stimuli at intensities and durations sufficient to produce, in six, repeated temporary threshold shifts (TTSs) from 15 to 25 dB and, in the remaining six, permanent threshold shifts (PTSs) from 10 to 20 dB. Thresholds were determined by means of an avoidance conditioning procedure similar to that of Clack and Herman (1963), in which observation intervals were signaled by the houselight and the animals required to press a bar if an auditory signal was presented, and to withold response if not. Following final behavioral testing, animals were sacrificed and the effect of the exposures upon hair cells was determined. This was accomplished with surface preparation techniques and phase microscopy. The organ of Corti was examined along its length and the number of missing and visibly damaged hair cells was determined for each of the inner and outer rows from a point 1 mm from the apex to a point 17 mm from the apex. There was no clear evidence of hair cell damage due to the exposure. It is concluded that pure‐tone stimulation sufficient to produce PTSs of 10–20 dB may not produce anatomical injuries to the organ of Corti that are detectable by phase microscopy.

ISSN:0001-4966    

DOI:10.1121/1.1913230

出版商:Acoustical Society of America    

年代:1972

数据来源: AIP