Efficacy of 3 commonly used hearing aid circuits - A crossover trial

Context Numerous studies have demonstrated that hearing aids provide significant benefit for a wide range of sensorineural hearing loss, but no carefully controlled, multicenter clinical trials comparing hearing aid efficacy have been conducted. Objective To compare the benefits provided to patients with sensorineural hearing loss by 3 commonly used hearing aid circuits. Design Double-blind, 3-period, 3-treatment crossover trial conducted from May 1996 to February 1998. Setting Eight audiology laboratories at Department of Veterans Affairs medical centers across the United States. Patients A sample of 360 patients with bilateral sensorineural hearing loss (mean age, 67.2 years; 57% male, 78.6% white). Intervention Patients were randomly assigned to 1 of 6 sequences of linear peak clipper (PC), compression limiter (CL), and wide dynamic range compressor (WDRC) hearing aid circuits. All patients wore each of the 3 bearing aids, which were installed in identical casements, for 3 months, Main Outcome Measures Results of tests of speech recognition, sound quality, and subjective hearing aid benefit, administered at baseline and after each 3-month intervention with and without a hearing aid. At the end of the experiment, patients ranked the 3 hearing aid circuits. Results Each circuit markedly improved speech recognition, with greater improvement observed for soft and conversationally loud speech (all 52-dB and 62-dB conditions, P less than or equal to .001). All 3 circuits significantly reduced the frequency of problems encountered in verbal communication. Some test results suggested that CL and WDRC circuits provided a significantly better listening experience than PC circuits in word recognition (P = .002), loudness (P = .003), overall liking (P = .001), aversiveness of environmental sounds (P = .02), and distortion (P = .02). In the rank-order ratings, patients preferred the CL hearing aid circuits more frequently (41.6%) than the WDRC (29.8%) and the PC (28.6%) (P = .001 for CL vs both WDRC and PC). Conclusions Each circuit provided significant benefit in quiet and noisy listening situations. The CL and WDRC circuits appeared to provide superior benefits compared with the PC, although the differences between them were much less than the differences between the aided vs unaided conditions.