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Acoustic distortion in the ear canal. I. Cubic difference tones: Effects of acute noise injury

 

作者: Richard A. Schmiedt,  

 

期刊: The Journal of the Acoustical Society of America  (AIP Available online 1986)
卷期: Volume 79, issue 5  

页码: 1481-1490

 

ISSN:0001-4966

 

年代: 1986

 

DOI:10.1121/1.393675

 

出版商: Acoustical Society of America

 

数据来源: AIP

 

摘要:

Acoustic emissions in the form of cubic difference tones (CDT’s), 2f1−f2, were measured in the ear canals of gerbils and cats. The state of the cochlea was manipulated by means of acute exposure to noise and was monitored with the aid of the whole‐nerve response to tone pips. The resulting shifts in the levels of emissions generated by pairs of primary tones of equal intensity were then compared to the corresponding threshold shifts of the whole‐nerve response across frequency. Data obtained from normal ears before injury indicate that the absolute thresholds of the whole‐nerve responses across frequency are not necessarily good predictors of theabsolutelevels of CDT emissions generated by 70‐ and 80‐dB SPL primaries. While high emission levels were often linked to low whole‐nerve thresholds in pre‐exposed ears, instances of animals with sensitive whole‐nerve thresholds coupled with very weak emissions were also found. Conversely, animals with poor whole‐nerve thresholds (shifted by up to 30 dB) could occasionally have high levels of emissions. After acute noise injury, however, theshiftsof emission levels as a function of the center frequency of the primary‐tone pair largely corresponded to the threshold shifts seen in the whole‐nerve response. In other words, the temporary level shift of an acoustic emission largely reflected the acute change to a specific cochlear region associated with the primary frequencies.

 

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