A Longitudinal Examination of Harmonic Distortion in Hearing Aids This study examined the harmonic distortion levels of 1170 hearing aids submitted to the Veterans Administration for contract evaluation during the last six fiscal years. Measurements were made, with a 75 dB SPL input, at 500, 700, and 900 Hz and at the frequency at which maximum distortion was found. ... Research Article
Research Article  |   December 01, 1967
A Longitudinal Examination of Harmonic Distortion in Hearing Aids
 
Author Affiliations & Notes
  • Roger N. Kasten
    Purdue University, Lafayette, Indiana
  • Stephen H. Lotterman
    Catholic University of America, Washington, D.C.
Article Information
Research Articles
Research Article   |   December 01, 1967
A Longitudinal Examination of Harmonic Distortion in Hearing Aids
Journal of Speech, Language, and Hearing Research, December 1967, Vol. 10, 777-781. doi:10.1044/jshr.1004.777
History: Received March 1, 1967
 
Journal of Speech, Language, and Hearing Research, December 1967, Vol. 10, 777-781. doi:10.1044/jshr.1004.777
History: Received March 1, 1967

This study examined the harmonic distortion levels of 1170 hearing aids submitted to the Veterans Administration for contract evaluation during the last six fiscal years. Measurements were made, with a 75 dB SPL input, at 500, 700, and 900 Hz and at the frequency at which maximum distortion was found. The gain of each aid was set with a 62.5 dB SPL input to that point at which distortion at all amplified frequencies was less than 10%. Based upon average gain and average saturation sound pressure level, each aid was placed in one of three power categories. The results show that the levels of maximum distortion appear to be inversely proportional to the rated power of the aids. Also, at all frequencies, the levels of harmonic distortion found in aids during the last two years generally equaled or exceeded those found in 1962, the first year for this study.

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