A DIGITAL FILTERBANK HEARING-AID - PREDICTING USER PREFERENCE AND PERFORMANCE FOR 2 SIGNAL-PROCESSING ALGORITHMS

Objective: In a series of experiments with a wearable binaural digital hearing aid, two hearing aid processing algorithms were compared. Bot h algorithms provided individual frequency shaping via a seven-band fi lterbank with compression limiting in the high-frequency channel, They differed in the processing of the low-frequency channel, using dynami c range compression for one (DynEar) and linear processing with compre ssion limiting for the other (LinEar), In a pilot field test we found that LinEar/DynEar preference based on use time could be predicted fro m auditory dynamic range data, For the subjects who preferred DynEar, the mean dynamic range was broader for low and mid frequencies and nar rower for high frequencies, as compared with the LinEar preference sub jects. These groupings were tested as predictors of user preference an d performance in a main field test. Design: The main study included 26 hearing aid users with symmetrical sensorineural losses. The algorith ms were compared in a one-mo-long blind field test, A data logger func tion was included for objective recording of the total time each algor ithm was used and how the volume controls were used. The pleference wa s based oil the time used for each algorithm and on subjective stateme nts, Threshold signal-to-noise ratio (S/N-threshold) for speech was te sted, and sound quality ratings were obtained through a questionnaire. We also tested the SN-thresholds for the subjects' conventional (own) aids, Results: The preference was correctly predicted by the dynamic range data on 12 out of 15 new cases, S/N-thresholds were lower for th e preferred fittings compared with the nonpreferred fittings and with the subjects' own aids. In the questionnaire the preferred fittings we re rated significantly higher in terms of overall impression and clear ness, Because of tile systematic way the DynEar-preference subjects ad justed the high-frequency DynEar gain, we speculate that upward spread of masking may have been a factor ill preference and performance. Add itionally, LinEar-preference subjects' preference and performance migh t have been influenced by excessive compression ratios with the DynEar processing in these cases. Conclusions: 1. Preference for DynEar vers us LinEar depends on the auditory dynamic range. 2. S/N-thresholds for speech were better for the preferred fittings, which also were rated higher in terms of overall impression of sound quality and clearness.