Lexical effects on the perceived clarity of noise-vocoded speech in younger and older listeners

Abstract

When listening to degraded speech, such as speech delivered by a cochlear implant (CI), listeners can make use of linguistic knowledge to facilitate speech recognition. Yet, the extent to which linguistic knowledge can be effectively used to compensate for degraded input may depend of the level of degradation and the age of the listener. The current study investigated lexical effects in the compensation for degraded speech via noise-vocoder simulations of CI hearing in younger and older normal-hearing listeners. In two online experiments, listeners rated the clarity of noise-vocoded sentences, with varying filter slopes. Lexical information was provided in the form of text priming and/or the lexical content (i.e., lexical frequency and neighborhood density) of key words in the sentences. Results showed that lexical information from both text priming and the lexical content enhanced the perceived clarity of degraded speech, but the strength of the lexical effects depended on the level of degradation. Additionally, lexical information appeared to equally benefit younger and older listeners. Findings demonstrate that lexical knowledge may be used in cognitive compensation during the recognition of noise-vocoded speech in both younger and older listeners. However, these mechanisms may not be as effective when the signal is highly degraded.