The Effects of Hearing Aid Compression Parameters on the Short-Term Dynamic Range of Continuous Speech

Abstract

The purpose of this study was to evaluate and quantitatively model the independent and interactive effects of compression ratio, number of compression channels, and release time on the dynamic range of continuous speech. A CD of the Rainbow Passage (J. E. Bernthal & N. W. Bankson, 1993) was used. The hearing aid was a programmable, digital, wide dynamic range compression instrument. A fully crossed design and multiple regression analyses were used to evaluate and model the effects of release time (32, 128, and 1024 ms), compression ratio (1:1, 2:1, and 4:1), and number of compression channels (1, 2, and 4 channels) on the short-term octave-band dynamic range of speech. Dynamic range of speech was defined as the range between the 1% and 70% exceedance levels within each octave band. As the compression ratio and number of channels increased, and as the release time decreased, the dynamic range of speech decreased. The effects of channels and release time increased as the compression ratio increased. In all conditions, the amount of effective compression for speech was less than the nominal compression ratio. A multiple regression model is provided that predicts the effects of various combinations of compression parameters on the dynamic range of speech.