Background: Multichannel wide dynamic range compression (WDRC) and ChannelFree processing have
similar goals yet differ significantly in terms of signal processing. Multichannel
WDRC devices divide the input signal into separate frequency bands; a separate level
is determined within each frequency band; and compression in each band is based on
the level within each band. ChannelFree processing detects the wideband level, and
gain adjustments are based on the wideband signal level and adjusted up to 20,000
times per second. Although both signal processing strategies are currently available
in hearing aids, it is unclear if differences in these signal processing strategies
affect the performance and/or preference of the end user.
Purpose: The purpose of the research was to determine the effects of multichannel wide dynamic
range compression and ChannelFree processing on performance and/or preference of listeners
using open-canal hearing instruments.
Research Design: An experimental study in which subjects were exposed to a repeated measures design
was utilized.
Study Sample: Fourteen adult listeners with mild sloping to moderately severe sensorineural hearing
loss participated (mean age 67 yr).
Data Collection and Analysis: Participants completed two 5 wk trial periods for each signal processing strategy.
Probe microphone, behavioral and subjective measures were conducted unaided and aided
at the end of each trial period.
Results: Behavioral and subjective results for both signal processing strategies were significantly
better than unaided results; however, behavioral and subjective results were not significantly
different between the signal processing strategies.
Conclusions: Multichannel WDRC and ChannelFree processing are both effective signal processing
strategies that provide significant benefit for hearing instrument users. Overall
preference between the strategies may be related to the degree of hearing loss of
the user, high-frequency in-situ levels, and/or acceptance of background noise.
Key Words
ChannelFree - compression - hearing aid - open canal
