The suitable acoustic gain and frequency response of a hearing aid in noise were studied in seven individuals with moderate sensorineural hearing loss. The test sounds consisted of a 57-word list mixed with three kinds of noises. Most comfortable loudness levels and speech discrimination scores were obtained corresponding to the different frequency responses of the hearing aid.
The results were summarized as follows. The acoustic gain of a hearing aid should be adjusted to the MCL, for adapting to a surrounding noise and its frequency response. Regardless of the kinds of the surrounding noises, the suitable frequency response of a hearing aid is commonly one with a low-frequency cut-off slope of 6-12dB/octave. It is to be desired that, if the frequency distribution of the surrounding noise which an individual encounters in daily life is estimated, the frequency response of a hearing aid in the individual case is appropriately adjusted in order to adapt to the surrounding noise and to improve the intelligibility of consonants.