Speech is an inherently dynamic signal and spectral dynamics are integral to perception of both consonants and vowels. The rate, direction, and extent of formant movements provide cues to consonant and vowel identity. The loss of peripheral auditory sensitivity, precise temporal processing, and frequency selectivity associated with hearing loss will disrupt the perception of formant movements. As a result, the reduction or elimination of dynamic spectral cues may impair speech understanding, especially in adverse listening conditions such as background noise or reverberation. The purpose of this program of research is to understand the perception of the dynamic spectral properties of speech by hearing-impaired listeners, with the long-term goal of improving speech understanding by these individuals in adverse listening conditions. The proposed research compares the performance of normally-hearing and hearing-impaired listeners on measures of speech understanding in the presence of different types of signal distortion, and speech understanding of signals with enhanced spectral dynamics. A computational model based on the amount of potential information available in speech will be used to quantify differences in speech intelligibility due to hearing status and stimulus characteristics. Experimental procedures will consist of tests identification accuracy and intelligibility for speech. Signals will be presented in quiet and in the presence of various type of background noise. In addition, normally-hearing listeners will be presented with signals that have been processed to simulate some of the effects of hearing impairment. Listeners will also complete experimental conditions with signals that have been processed to enhance spectral dynamics. The information obtained by this program of research will have possible implications for the development of new hearing aid processing strategies and rehabilitative auditory training programs that may enhance speech intelligibility and reduce listening effort in hearing-impaired Veterans.