Relative Effectiveness of Three Stimulus Variables for Locating a Moving Sound Source

Abstract

A study is reported in which it is shown that observers can use at least three types of acoustic variables that indicate reliably when a moving sound source is passing: interaural temporal differences, the Doppler effect, and amplitude change. Each of these variables was presented in isolation and each was successful in indicating when a (stimulated) moving sound source passed an observer. These three variables were put into competition (with each indicating that closest passage occurred at a different time) in an effort to determine their relative importance. It was found that amplitude change dominated interaural temporal differences which, in turn, dominated the Doppler effect stimulus variable. The results are discussed in terms of two interpretations. First, it is possible that subjects based their judgements on the potential discriminability of each stimulus variable. However, because the stimuli used involved easily discriminable changes, subjects may instead have based their judgements on the independence of a stimulus variable from different environmental situation conditions. The dominance ordering obtained supports the second interpretation.

Looming Biases in Monkey Auditory Cortex

“…1 A). Hereafter, we will refer to the rising-intensity complex tones as the "looming" signal and the falling-intensity complex tones as the "receding" signals, because this cue alone seems to elicit the corresponding percepts (Rosenblum et al, 1987;Neuhoff, 2001). The amplitude envelopes for all stimuli either rose or fell quadratically over a period of 1000 ms. Figure 1, C and D, shows the frequency spectra of the complex tones (fundamental frequency, 1000 Hz) and white noise, respectively.…”

“…As a sound source approaches/recedes, intensity at the ears of the observer rises/ falls. Although other cues, like interaural and reverberatory cues, can also be important for localizing moving sound sources, dynamic intensity change is the dominant and most effective cue for detecting sound source motion in depth (Rosenblum et al, 1987;Zakarauskas and Cynader, 1991;Lufti and Wang, 1999). Thus, looming sound sources are best characterized by rising intensity sounds and receding sources by falling-intensity sounds, and looming events take place at time scales from hundreds of milliseconds to seconds.…”

“…The increased saliency is evident in increased attention toward looming sounds, estimation of time to arrival, and/or estimation of loudness change. For example, when subjects are required to use dynamic intensity cues to indicate the time to arrival of a looming sound source, they consistently err on the side of safety (Rosenblum et al, 1987;Schiff and Oldak, 1990;Neuhoff, 2001). Importantly, these perceptual biases are only evident when the sounds have some spectral structure; rising/falling-intensity white noise stimuli do not elicit the percepts of looming/receding and do not reveal any perceptual biases (Neuhoff, 1998;Ghazanfar et al, 2002;Maier et al, 2004).…”

Multidimensional processing of dynamic sounds: more than meets the ear

“…Change rates in sound amplitude and visual image size are the most reliable auditory and visual cues to motion in depth (Regan & Beverley, 1978;Rosenblum et al, 1987) that covary when a signal source moves closer or away from an observer (Zetzsche et al, 2002). Looming sounds (typically, an increase in amplitude) can serve as a warning of impending contact (Bach, Schachinger, Neuhoff, Esposito, Di Salle, Lehmann & Seifritz, 2008;Ghazanfar, Neuhoff & Logothetis, 2002) and are more likely to speed up responses, bias attention and change distance estimates (Ghazanfar et al, 2002;Maier et al, 2004;Neuhoff, 1998Neuhoff, , 2001, and induce stronger neural activation than are receding or constant sounds (Bach et al, 2008;Maier et al, 2008;Maier & Ghazanfar, 2007;Seifritz et al, 2002).…”

“…Participants were asked to detect a change in amplitude in the presented sound, regardless of the direction of change, while ignoring an irrelevant concurrent visual cue (a disk growing, shrinking, or not changing in size). These cueschanges in sound amplitude and the size of visual imagesare the most salient cues to auditory and visual motion in depth (Regan & Beverley, 1978;Rosenblum, Carello & Pastore, 1987). Because both sounds with rising amplitude and visual images that grow in size are associated with an approaching/looming motion, whereas both fallingamplitude sounds and visual images that shrink in size are associated with a departing/receding motion, henceforth, we refer to auditory and visual cues that converge in the direction of change as congruent (e.g., rising-amplitude sounds and growing disks) and cues that diverge in the direction of change as incongruent (e.g., rising-amplitude sounds and shrinking disks).…”