Level considerations for chimeric processing: Temporal envelope and fine structure contributions to speech intelligibility

Chimeric processing is used to assess the respective role of the acoustic temporal envelope (ENV) and the temporal fine structure (TFS) by adding noise to either component. An acoustic analysis demonstrates that adding noise to the ENV results in noise degradation of the ENV and overall signal attenuation, whereas adding noise to the TFS results in only noise degradation of the TFS. Young normal hearing adults were then tested using a modified chimeric strategy to maintain speech levels. Results partially confirm the primary role of the ENV in determining speech intelligibility but demonstrate significant TFS contributions during selective ENV masking.