Perceptual simultaneity range as a function of frequency separation and frequency range for two tones

When two tones start with a small onset asynchrony, one might perceive them as starting simultaneously. The range of this perceptual synchrony is defined as a perceptual simultaneity range (PSR), within which two tones are perceived as simultaneous. Our earlier study found V-shaped behavior of the PSR as a function of frequency separation (Delta f) for two tones. For this study, we investigated the PSR as a function of frequency separation (Delta f) and frequency range (F1). The PSR was measured using the simultaneity judgment task. Results demonstrated that the PSR decreases steeply and then increases gradually along the Delta f axis. Its breakpoint appeared at circa 0.5 critical bandwidth (CB), irrespective of F1. The PSR-Delta f curves for different F1 were almost coincident for Delta f <= 0.5 CB. The coincident decrease of the PSR for small Delta f supports the notion that the cochlear interference affects the perception of simultaneity.