Comparison of dual-time-constant and fast-acting automatic gain control (AGC) systems in cochlear implants.

Full Abstract

Cochlear implants usually employ an automatic gain control (AGC) system as a first stage of processing. AGC1 was a fast-acting (syllabic) compressor. AGC2 was a dual-time-constant system; it usually performed as a slow-acting compressor, but incorporated an additional fast-acting system to provide protection from sudden increases in sound level. Six experienced cochlear-implant users were tested in a counterbalanced order, receiving one-month of experience with a given AGC type before switching to the other type. Performance was evaluated shortly after provision of a given AGC type and after one-month of experience with that AGC type. Questionnaires, mainly relating to listening in quiet situations, did not reveal significant differences between the two AGC types. However, fixed-level and roving-level tests of sentence identification in noise both revealed significantly better performance for AGC2. It is suggested that the poorer performance for AGC1 occurred because AGC1 introduced cross-modulation between the target speech and background noise, which made perceptual separation of the target and background more difficult.

Author information

Author/s: Boyle, Patrick J (PJ); Büchner, Andreas (A); Stone, Michael A (MA); Lenarz, Thomas (T); Moore, Brian C J (BC);

Affiliation: Department of Experimental Psychology, University of Cambridge, Downing Street, Cambridge, UK. patrickb(-atsign-)abionics.fr

Journal and publication information

Publication Type: Comparative Study; Journal Article; Research Support, Non-U.S. Gov't

Journal: International journal of audiology (Int J Audiol), published in England. (Language: eng)

Reference: 2009-Apr; vol 48 (issue 4) : pp 211-21

Dates: Created 2009/04/13; Completed 2009/06/18;

PMID: 19363722, status: MEDLINE (last retrieval date: 6/18/2009, IMS Date: 18 Jun 2009 00:00:00)

Sourced from the National Library of Medicine. Abstract text and other information may be subject to copyright.

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