Amplitude envelope and subjective duration: Quantifying the role of decaying offsets in timing perception

Although duration perception is well-researched in the auditory literature, many experiments ostensibly exploring generalized processing use one type of tone-simplistic "beeps" with abrupt offsets. This leaves unaddressed the question of how we perceive duration when listening to the types of temporally complex sounds common in everyday listening. Here, we investigate the point of equivalence for the duration of steady state (aka "flat") and more natural decaying (aka "percussive") tones. Through this, we (1) gain further insight into amplitude envelope's role in duration perception and (2) provide guidance useful for future studies moving beyond simplistic tones with flat amplitude envelopes. Specifically, we conduct a series of 2-alternative forced-choice adaptive staircase procedures across three experiments, with participants deciding which of two tones sound longer. Experiment 1 uses sounds matched in amplitude envelope (homogenous, N = 54), and Experiment 2 uses mismatched sounds (heterogenous, N = 55). In Experiment 3, participants completed both homogenous and heterogenous conditions across 10 sessions (N = 5). The heterogenous data illustrate a two-parameter linear equation ( $y=110+1.31x$ ) best describes the point of subjective equality between flat and percussive tones, with model comparisons suggesting most unexplained variance can be attributed to individual differences. Together, these findings provide a useful step towards clarifying the perception of tones with amplitude envelopes more complex than those traditionally used in auditory perception studies, which holds important implications for both our theoretical understanding of perceived timing as well as ongoing applied work on improving hospital medical device sounds (which often use flat tones).