Modulation masking in cochlear implant listeners: envelope versus tonotopic components.

Full Abstract

It is hypothesized that channel-interaction in cochlear implant listeners as measured in a modulation-masking experiment would be influenced by both the tonotopic overlap between masker and signal as well as an interaction between their envelopes. Two experiments were conducted to measure the effects of maskers with noisy and steady-state envelopes on modulation detection by four adult Nucleus-22 cochlear implant listeners, as a function of tonotopic distance between the masker and the signal. In the first experiment, we measured detection thresholds for a 50-Hz modulation in the envelope of a 500-Hz carrier pulse train, in the presence of a masker stimulating regions basal and apical to, as well as overlapping with, the signal. The maskers had two kinds of envelopes:
(i) amplitude-modulated by flat-spectrum noise (NAM) and (ii) steady-state (SS(peak)) at a level corresponding to the maximum of the noise fluctuation range. In general, modulation thresholds obtained in the presence of the NAM maskers significantly exceeded thresholds obtained with the corresponding SS(peak) maskers. The ratio p of the threshold modulation depth m obtained with the NAM masker to that obtained with the SS(peak) masker was defined as a conservative index of "envelope masking." In the second experiment, p was determined for two different tasks:
the detection of modulation at 20 Hz and steady-state intensity increment detection. Compared to the 50-Hz modulation detection results, the ratio p was reduced for the 20-Hz modulation detection task and even more so for the steady-state increment detection task. It is concluded that channel-interaction can be significantly increased in cochlear implant listeners when dynamic stimuli are used in place of steady-state stimuli.

Learn Faster Today Improve your study skills

Author information

Author/s: Chatterjee, Monita (M);

Affiliation: Department of Auditory Implants and Perception, House Ear Institute, 2100 West Third Street, Los Angeles, California 90057, USA. monita@hei.org

Grants: N01DC92100-03 (Agency:United States NIDCD) ; R01DC004786-01 (Agency:United States NIDCD) ; R01DC01526-S1 (Agency:United States NIDCD) ; R03DC03519-03 (Agency:United States NIDCD)

Journal and publication information

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

Journal: The Journal of the Acoustical Society of America (J Acoust Soc Am), published in United States. (Language: eng)

Reference: 2003-Apr; vol 113 (issue 4 Pt 1) : pp 2042-53

Dates: Created 2003/04/21; Completed 2003/07/07; Revised 2007/11/14;

PMID: 12703715, status: MEDLINE (last retrieval date: 11/6/2008)

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

External Links for this article (including full text providers, if available):

Click Electronic Full-text Provider Links to see options for finding the electronic full text links to this article. Note there may be a subscription or fee required for access to the full text. See our FAQ for information on finding FREE full text articles.

This article may also be located in paper journal collections available in many libraries. Use the Journal and Publication Information above to find the full article.

MeSH headings (categories)

This article was linked to the MESH Headings shown below.

This article has not been indexed for related articles as yet, however you can still use the live related article search links below.

See 100+ related articles.