A multi-center, double blind clinical trial comparing benefit from three commonly used hearing aid circuits.
OBJECTIVE
Although numerous studies have demonstrated that hearing aids provide significant benefit, carefully controlled, multi-center clinical trials have not been conducted. A multi-center clinical trial was conducted to compare the efficacy of three commonly used hearing aid circuits: peak clipping, compression limiting, and wide dynamic range compression.


METHODS
Patients (N = 360) with bilateral, sensorineural hearing loss were studied using a double blind, three-period, three-treatment crossover design. The patients were fit with each of three programmable hearing aid circuits. Outcome tests were administered in the unaided condition at baseline and then after 3 mo usage of each circuit, the tests were administered in both aided and unaided conditions. The outcome test battery included tests of speech recognition, sound quality and subjective scales of hearing aid benefit, including patients' overall rank-order rating of the three circuits.


RESULTS
Each hearing aid circuit improved speech recognition markedly, with greater improvement observed for soft and conversationally loud speech in both quiet and noisy listening conditions. In addition, a significant reduction in the problems encountered in communication was observed. Some tests suggested that the two compression hearing aids provided a better listening experience than the peak clipping hearing aid. In the rank-order ratings, patients preferred the compression limiting hearing aid more frequently than the other two hearing aids.


CONCLUSIONS
The three hearing aid circuits studied provide significant benefit both in quiet and in noisy listening situations. The two compression hearing aids appear to provide superior benefits compared to the linear circuit, although the differences between the hearing aids were smaller than the differences between unaided and aided conditions.
Howard Leight Industries, San Diego, California 92154, USA.
Vernon D
VD
Larson
David W
DW
Williams
William G
WG
Henderson
Lynn E
LE
Luethke
Lucille B
LB
Beck
Douglas
D
Noffsinger
Gene W
GW
Bratt
Robert A
RA
Dobie
Stephen A
SA
Fausti
George B
GB
Haskell
Bruce Z
BZ
Rappaport
Janet E
JE
Shanks
Richard H
RH
Wilson
D000368:Aged; D018592:Cross-Over Studies; D004311:Double-Blind Method; D005260:Female; D006310:Hearing Aids; D006312:Hearing Loss, Bilateral / Q000175:diagnosis / Q000534:rehabilitation; D006319:Hearing Loss, Sensorineural / Q000175:diagnosis / Q000534:rehabilitation*; D006801:Humans; D008297:Male; D012720:Severity of Illness Index; D013067:Speech Perception