Comparing Processing Strategies
Plyler et al (2013) evaluated 14 adult listeners (mean age 67 years) with mild to moderately severe sensorineural hearing loss (SNHL) with regard to determining the effects of "ChannelFree" vs. "Multichannel Wide Dynamic Range Compression (M-WDRC)" processing strategies. Subjects used each processing strategy for five weeks and were (then) evaluated using probe microphone measures and subjective and behavioral measures in aided and unaided conditions.
The authors note that M-WDRC divides the input signal into multiple frequency bands, a loudness level is determined for each frequency band and compression is applied (as directed by the programming). When using M-WDRC, "trade-offs" can occur between speech intelligibility (fast acting) and listening comfort (slow acting). Of note, ChannelFree processing is based on the overall wideband signal loudness level and can be adjusted 20,000 times per second, essentially avoiding overshoot and spectral distortion.
Plyler et al report that both strategies (M-WDRC and ChannelFree) were effective and both provided comparable speech perception improvements in quiet and noise. They report "…performance with multichannel WDRC was not significantly different than performance with ChannelFree processing on any of the subtests." Additionally, the authors report satisfaction and preference ratings were not significantly different across the two processing strategies.
For More Information, Recommendations, and References
Plyler PN, Reber MB, Kovach A, Galloway E, Humphrey E. (2013) Comparison of Multichannel Wide Dynamic Range Compression and ChannelFree Processing in Open Canal Hearing Instruments. Journal of the American Academy of Audiology 24:126-137.