Auditory temporal capabilities and sentence intelligibility in the elderly

The purpose of this investigation was to study age-related changes in certain auditory temporal processing abilities of listeners. The relationship between temporal processing and auditory object formation in speech perception also was investigated. Two experiments were conducted to investigate these issues. Evaluation of temporal capabilities in a speech perception task was measured by studying the effect of amplitude modulation on sentence intelligibility. Time-varying sinusoidal (TVS) replicas of natural speech served as baseline stimuli for Experiments 1 and 2. The TVS sentences remained either unmodulated or were amplitude modulated at 100 Hz in Experiment 1, or were modulated at 10 and 100 Hz in Experiment 2. Improvement in intelligibility due to amplitude modulation is called Modulation Intelligibility Improvement (MII). In Experiment 1, MII was compared with gap detection abilities in two groups of participants: elderly listeners wearing hearing aids and young adults with normal hearing. In Experiment 2, MII was compared with comodulation masking release (CMR) in three groups of participants: elderly with normal hearing, elderly listeners with hearing impairment not wearing hearing aids, and young adults with normal hearing. Experiment 1 showed no difference on the gap detection abilities between the elderly and young listeners. Sentence intelligibility results indicated amplitude modulation interfered with elderly listeners\u27 ability to understand TVS sentences while it improved intelligibility for younger listeners. In Experiment 2, CMR was demonstrated at the 10 Hz modulation rate. Amplitude modulation improved sentence intelligibility with the largest MII effect at 100 Hz. CMR and MII were only correlated in young listeners at modulation rates of 10 Hz. All listeners, except for those wearing hearing aids during the study, were able to use amplitude modulation to improve sentence intelligibility