Comparison of interaural time difference thresholds for speech, speech spectrum noise, and pure tones

Abstract

The interaural time difference threshold for speech has been reported to be approximately 30 μsec [E. Cherry and B. Sayers, J. Acoust. Soc. Am. 28, 889&–895 (1956)]. This value is substantially larger than the 10‐μsec figure reported for broad band noise signals by other experimenters [e.g., R. Klumpp and H. Eady, J. Acoust. Soc. Am. 28, 859–860 (1956)]. In the two studies just mentioned, however, different subjects and psychoacoustical methods were employed; thus, it is unclear as to whether larger Δt's are indeed needed to lateralize speech signals. The purpose of this experiment, therefore, was to compare lateralization performance for speech and nonspeech stimuli. Interaural time difference thresholds were obtained for speech, speech‐spectrum noise, speech‐modulated noise, and 200‐, 500‐, and 1000‐Hz sinusoids for the same subjects using a 2IFC experimental paradigm. Under these conditions, speech and speech‐modulated noise yielded essentially the same interaural time difference thresholds. In addition, smaller Δt's for 75% correct performance were needed for the broad band noise than for the pure tone stimuli. [Supported by a grant from NINCDS.]