Increased perception of loudness in autism.

Clinical reports on autism describe abnormal responses to auditory stimuli such as intolerance to sounds. The present study assessed subjective perception of loudness in subjects with autism compared to healthy controls, using two psychoacoustic tests. First, the auditory dynamic range was evaluated at six different tone frequencies. Secondly, loudness growth as a function of the intensity level of a 1 kHz tone was estimated. Verbal responses from a group of 11 children and adolescents with autism were compared to responses of 11 age- and gender- matched healthy controls. Smaller auditory dynamic ranges were found in the autistic group than in the control group, as well as increased perception of loudness, indicating hyperacusis in subjects with autism.