Preferred real-ear insertion gain on a commercial hearing aid at different speech and noise levels

In the present study, we measured preferred real-ear insertion gain (REIG) under different levels of speech and noise to assess whether current automatic gain control (AGC) and automatic signal processing (ASP) hearing aids are operating optimally. Preferred REIG for optimal speech clarity was determined under seven speech and noise conditions. In four conditions, speech (discourse passages) was varied from 55 dB SPL to 85 dB SPL in 10-dB steps at a fixed signal-to-noise ratio (S/N) of +5. In the remaining conditions, speech was fixed at 65 dB SPL while the noise level was varied in 5-dB steps to yield S/Ns from +10 to -5. The results showed that subjects selected less gain as speech or noise levels were increased. In general, less overall gain was selected as speech level was increased, and less overall gain, especially in the low-frequency region, was selected as the S/N ratio became progressively poorer. These results are discussed in relation to how hearing aids with adaptive frequency/gain responses should respond to varying input levels to achieve optimal clarity of speech.