Title page for ETD etd-1112103-083723

Type of Document Master's Thesis
Author Hill, Ashley B.
Author's Email Address ahill4@lsu.edu
URN etd-1112103-083723
Title The Effects of Expansion on Objective and Subjective Benefit in Hearing-Impaired Listeners
Degree Master of Arts (M.A.)
Department Communication Sciences & Disorders
Advisory Committee
Advisor Name Title
Paul Hoffman Committee Chair
Hugh Buckingham Committee Member
Jana Oetting Committee Member
  • time constants
  • digital hearing aids
  • expansion
Date of Defense 2003-11-03
Availability unrestricted
The present research involves two studies. Twenty hearing-impaired participants were divided into two groups depending on their audiometric data and binaurally fit with the Starkey Endeavour 3211 hearing instruments. Experiment I was designed to determine if the use of expansion technology affected objective and subjective benefit in hearing-impaired listeners. Probe microphone measures were obtained at 40, 50, and 60 dB SPL and with the speaker deactivated to ensure that the expansion feature was functioning. Listener performance was measured in quite using the Connected Speech Test (CST) and in noise using the Hearing in Noise Test (HINT) at 40, 50, and 60 dB SPL with expansion activated and deactivated. Participants were also asked to participate in a subjective portion of the experiment. They filled out a rating form twice a day in two settings: quiet and in noise, with expansion activated and deactivated. Results indicated that expansion negatively affected user performance, but participants significantly preferred the feature.

Experiment II, very similar in design, examined expansion time constants and their effects on objective and subjective benefit in hearing-impaired listeners. Experiment II examined four different expansion time constants (128 ms, 512 ms, 2048 ms, 4056 ms) to determine their role on speech intelligibility in quiet and in noise with two levels of hearing-impaired subjects (one group was worse than the other). The CST and the HINT were administered at 65 dB SPL to determine listener performance. A similar subjective rating form was used in Experiment II. Participants were asked to rate the speed of the gain and/or reduction of gain in quiet and in noise while speaking and listening. Results indicated that as expansion time constants lengthened performance decreased. Results indicated that there was no preferred time constant and that as the time constant lengthened performance decreased.

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