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Abstract

Sounds with rising intensities are known to be more salient than their constant amplitude counterparts [Seifritz et al., 2002]. Incorporating a time-to-contact characteristic into the rising profile can further increase their perceived saliency [Gray, 2011]. We investigated whether looming sounds with this time-to-contact profile might be especially effective as warning signals. Nine volunteers performed a primary steering task whilst occasionally discriminating oriented Gabor patches that were presented in their visual periphery. These visual stimuli could be preceded by an auditory warning cue, 1 second before they appeared. The 2000 Hz tone could have an intensity profile that was either constant (65 dB), linearly rising (60 - 75 dB, ramped tone), or exponentially increasing (looming tone). O verall, warning cues resulted in significantly faster and more sensitive detections of the visual targets. More importantly, we found that EEG potentials to the looming tone were significantly earlier and sustained for longer, compared to both the constant and ramped tones. This suggests that looming sounds are processed preferentially because of time-to-contact cues rather than rising intensity alone.