Speech-in-noise perception in high-functioning individuals with autism or Asperger's syndrome.

ABSTRACT

BACKGROUND: High-functioning individuals with autism (HFA) or Asperger's syndrome (AS) commonly report difficulties understanding speech in situations where there is background speech or noise. The objective of this study was threefold (1) to verify the validity of these reports; (2) to quantify the difficulties experienced; and (3) to propose possible mechanisms to explain the perceptual deficits described. METHOD: Speech-in-noise perception abilities were measured using speech reception thresholds (SRTs), defined as the speech-to-noise ratio (SNR) at which approximately 50% of the speech is correctly identified. SRTs were measured for 11 individuals with HFA/AS and 9 age/IQ-matched normal-hearing control subjects, using an adaptive procedure, in a non-reverberant sound-attenuating chamber. The speech materials were standardised lists of everyday sentences spoken by a British male speaker. The background sounds were (1) a single female talker; (2) a steady speech-shaped noise; (3) a speech-shaped noise with temporal dips; (4) a steady speech-shaped noise with regularly spaced spectral dips; and (5) a speech-shaped noise with temporal and spectral dips. RESULTS: SRTs for the HFA/AS group were generally higher (worse) than those for the controls, across the five background sounds. A statistically significant difference in SRTs between the subject groups was found only for those background sounds that contained temporal or spectro-temporal dips. SRTs for the HFA/AS individuals were 2 to 3.5 dB higher than for the controls, equivalent to a substantial decrease in speech recognition. Expressed another way, the HFA/AS individuals required a higher SNR, whenever there were temporal dips in the background sound, to perform at the same level as the controls. CONCLUSIONS: The results suggest that the speech-in-noise perception difficulties experienced by individuals with autism may be due, in part, to a reduced ability to integrate information from glimpses present in the temporal dips in the noise.