The roles of temporal envelope and fine structure information in auditory perception

Within the cochlea, broadband sounds like speech and music are filtered into a series of narrowband signals, each with a relatively slowly varying envelope (ENV) imposed on a rapidly oscillating carrier (the temporal fine structure, TFS). Information about ENV and TFS is conveyed in the timing and short-term rate of action potentials in the auditory nerve. This paper describes the role of ENV and TFS information in pitch perception, binaural processing, and the perception of speech in the presence of background sounds. The paper also describes the effects of hearing loss and age on the processing of TFS and ENV information. The monaural and binaural processing of TFS information is adversely affected by both hearing loss and increasing age. The monaural processing of ENV information is little affected by hearing loss or by increasing age. The binaural processing of ENV information deteriorates somewhat with increasing age but is not markedly affected by hearing loss. The reduced TFS processing abilities found for older/hearing-impaired subjects may partially account for the difficulties that such subjects experience in complex listening situations.