Effects of Age on the Discrimination of Amplitude and Frequency Modulation for 2- and 10-Hz Rates

Frequency modulation (FM) at a rate of 10 Hz may be detected via conversion of FM to amplitude modulation (AM) in the cochlea, while 2-Hz FM may be detected partly using temporal fine structure (TFS) information. Greater age may impair the processing of TFS information while sparing the processing of AM information. To test these ideas while controlling for the effects of detection efficiency, a two-stage experiment was conducted. In stage 1, psychometric functions were measured for the detection of AM alone and FM alone imposed on a 1-kHz carrier, using 2- and 10-Hz rates. In stage 2, the task was to discriminate AM from FM at the same modulation rate when the detectability of the AM alone and FM alone was equated. For young normal-hearing subjects, discrimination was consistently better for the 2- than for the 10-Hz rate. Some older subjects with normal hearing at 1 kHz showed a similar pattern but others showed no clear difference in AM-FM discrimination for the 2- and 10-Hz rates. The results are consistent with the idea that greater age reduces the ability to use TFS cues for some but not all people.

© 2018 The Author(s). Published by S. Hirzel Verlag · EAA. This is an open access article under the terms of the Creative Commons Attribution (CC BY 4.0) license (https://creativecommons.org/licenses/by/4.0/).