Quality rating test of hearing aid benefit in the NIDCD/VA Clinical Trial.

Objective: As part of a large clinical trial that compared three hearing aid circuits using several evaluation methods, judgments about quality of listening experiences were sought from all subjects. Three dimensions were examined: loudness, noise interference and overall liking (quality).

Design: Eight Audiology units in VA Medical Centers participated. Three hearing aid circuits were compared: linear peak clipper, compression limiter, and wide dynamic range compressor. The experimental design was a three-period, three-treatment crossover design. Baseline measures were made using a battery of tests in unaided conditions. Subjects (N = 360) were then stratified by participating site and randomized to one of six sequences of the three hearing aid circuits. Each circuit was fit binaurally and all subjects used each of the three circuits for 3 mo. All outcome measures were administered in unaided and aided conditions after each 3-mo period. The study used a double-blind strategy, i.e., neither the audiologist giving the tests nor the subject knew which circuit was being used. A different audiologist programmed the devices.

Results: For loudness judgments, soft and loud presentations of speech in quiet and in babble competition were judged more comfortable via the wide dynamic range circuit. The noise interference tasks and overall liking of the listening experience showed few significant differences across circuits. All circuits made the listening experience more comfortably loud for soft and conversation-level speech.

Conclusions: Differences across circuits in terms of the overall quality of the listening experience and how noise interference was rated were small. Only isolated conditions, usually favoring the WDRC circuit, reached significance levels. The loudness dimension results were clearer. The WDRC circuit made sounds at either the loud or soft extreme more comfortable. When subjects were grouped by amount and configuration of hearing loss, the advantages for the WDRC and to a lesser extent the linear compression-limited circuit were clearest among subjects with mild hearing losses with a >10 dB/octave high-frequency drop, and those with moderate, relatively flat hearing losses.