Input Stimuli for Obtaining Frequency Responses of Automatic Gain Control Hearing Aids Developing a family of frequency response curves for AGC types of hearing instruments using swept pure tones at varying input levels often produces erroneous results. This problem is caused by exceeding the threshold for activating the AGC circuit at some frequencies but not at other frequencies during the pure-tone sweep, ... Research Note
Research Note  |   March 01, 1989
Input Stimuli for Obtaining Frequency Responses of Automatic Gain Control Hearing Aids
 
Author Affiliations & Notes
  • David A. Preves
    Argosy Electronics
  • Lucille B. Beck
    Veterans Administration
  • Edwin D. Burnett
    National Bureau of Standards
  • Harry Teder
    Telex Communications
Article Information
Research Notes
Research Note   |   March 01, 1989
Input Stimuli for Obtaining Frequency Responses of Automatic Gain Control Hearing Aids
Journal of Speech, Language, and Hearing Research, March 1989, Vol. 32, 189-194. doi:10.1044/jshr.3201.189
History: Received May 10, 1988 , Accepted October 7, 1988
 
Journal of Speech, Language, and Hearing Research, March 1989, Vol. 32, 189-194. doi:10.1044/jshr.3201.189
History: Received May 10, 1988; Accepted October 7, 1988

Developing a family of frequency response curves for AGC types of hearing instruments using swept pure tones at varying input levels often produces erroneous results. This problem is caused by exceeding the threshold for activating the AGC circuit at some frequencies but not at other frequencies during the pure-tone sweep, thereby producing a different frequency response from that which would be obtained with a complex input signal such as speech-shaped noise. This measurement artifact may be minimized by ensuring that the threshold for activating the AGC circuit is either always exceeded or never exceeded during the development of a frequency response curve. Three input signals are compared for developing a family of frequency responses for an AGC hearing aid: (1) swept pure tone, (2) swept pure tone with bias tone added, and (3) shaped broad-band noise. The shaped broad-band noise appears to be the input signal of choice.

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