Listeners can move from room to room while conversing, encountering changes in the acoustics of their surroundings. In order to maintain speech intelligibility when faced with changing noises and reverberation listeners may rapidly adapt by building and updating a model of their surrounding auditory space. We have previously demonstrated rapid adaptation to a change in the acoustic environment, consisting of a brief decrease and then a recovery in intelligibility. In the current study we investigated whether the amount and time-course of this adaptation changes as a function of age and/or hearing impairment, and whether the amount of reverberation or the complexity of the background noise would affect adaptation time. We asked 29 normal-hearing and 37 hearing-impaired listeners to identify an ongoing stream of random target words, presented at a rate of one every 1.5 seconds, while the acoustic environment was switched every nine seconds. On average, intelligibility dropped by 16% upon entering a new environment before recovering to ceiling performance within 2.3 seconds. These results were not affected by hearing impairment or age. Preliminary analyses suggest that listeners may require additional time to adapt noises of greater complexity. [Work supported by MRC (U135097131) and the Chief Scientist Office (Scotland).]

In natural listening environments, the background noises and the acoustic spaces they occupy can vary greatly, both in their characteristics and in their impact on speech intelligibility. It has been suggested that listeners build up a statistical representation of ongoing noises; however, listeners can move around a room or move from one room to another, constantly changing both the background noises and the reverberation around them. If listeners are to make use of such statistics to aid in speech intelligibility, they must engage in a constant adaptation. We asked normal and hearing-impaired listeners to identify in real-time a stream of random target words in a contiguous series of novel acoustic environments lasting 13 s each, thus measuring the extent and time-course of changes in speech intelligibility that listeners experience in a new environment. The results from our task demonstrate that most listeners experience a rapid increase in speech intelligibility over several seconds of exposure to certain acoustic environments, but not to others. This suggests that there are classes or types of noises and reverberations that can be adapted to over a short time course and others that cannot. [Work supported by the MRC and the CSO.]