Title

Effect of dynamic compression characteristics on aided perception of reverberant speech

Date of Award

12-2006

Degree Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Communication Sciences and Disorders

Advisor(s)

Karen A. Doherty

Keywords

Dynamic compression, Reverberant, Speech, Hearing aid

Subject Categories

Speech Pathology and Audiology

Abstract

The dynamic characteristics of compression, attack time (AT) and release time (RT), have been shown to temporally alter speech signals. The current study examined the effect of AT/RT on the intelligibility and clarity of reverberant speech in a laboratory and field study.

Thirty listeners with sensorineural hearing loss were monaurally fitted with a Siemens Triano3 behind-the-ear hearing aid, programmed in linear (AT = 0 ms, RT = 0 ms), fast compression (AT = 9 ms, RT = 90 ms), and slow compression (AT = 900 ms, RT = 1500 ms) settings. Low-predictability Speech-Perception-in-Noise sentences were presented at four reverberation times (RT60s) to simulate an anechoic room (RT 60 = 0 s), living-room (RT 60 = 0.6 s), classroom (RT 60 = 1.2 s), and hard hall (RT 60 = 3.6 s) (Sandridge, Newman, Spitzer, & Katz, 2005). Twelve listening conditions (3 AT/RT settings × 4 RT 60 s) were tested. Intelligibility scores were based on correct identification of the last word in each sentence. Listeners also rated the clarity of the sentences using a subscale of the Judgment-of-Sound-Quality measure (Gabrielsson Schenkman, & Hagerman, 1988).

In the field trial, twenty of the 30 listeners were binaurally fitted with the Triano3 hearing aids. Listeners wore the Triano3 for one week set in syllabic compression and one week set in dual compression in a random order. Also, listeners kept a journal of their listening experiences and completed the Abbreviated Profile of Hearing Aid Benefit (APHAB) (Cox & Alexander, 1995) after each week. At the end of the field trial, listeners identified the setting they preferred.

The primary results from this study were: (1) intelligibility scores and clarity ratings of reverberant speech were similar regardless of AT/RT; (2) reverberation significantly reduced speech intelligibility and clarity across all hearing-aid settings; (3) slow AT/RT yielded greater real-ear aided response than fast AT/RT despite the same prescribed gain; (4) APHAB and journal entries showed greater benefit for syllabic compression than dual compression; (5) 85% of the listeners preferred syllabic compression over dual compression; and (6) listeners who obtained low intelligibility scores of reverberant sentences demonstrated high benefit in everyday listening wearing syllabic compression.

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