High- and Low-Frequency Decrement Contribution to Spectral Enhancement.

Purpose: The relative benefit of a single, flanking, high- or low-frequency decrement was assessed to better understand properties of spectral enhancement that may aid in algorithm design.

Method: Detection thresholds were measured for intensity increments applied to a narrow target band of frequencies embedded in a broadband signal while 400-Hz-wide, 9- or 12-dB-deep intensity decrements were placed above, below, or on both sides of the target band. A mono condition with no decrements was used as a control. Eight participants with normal hearing and 8 participants with hearing impairment took part in this experiment.

Results: Performance improved in the presence of decrements for both groups and was equivalent for both high- or low-frequency decrements. Comparison with individually measured auditory filters revealed that participants with normal hearing made use of energy cues available within these filters, whereas some participants with hearing impairment, despite improved increment detection, underutilized this information.

Conclusion: Inclusion of a single, adjacent, high- or low-frequency decrement improved increment detection but not to the same extent as when decrements flanked both sides.