onset

Onset is the human-constructed concept marking the temporal beginning — the attack phase — of a sound event. It identifies the transition from silence or non-sound to audible sound, and is used extensively in acoustics, music perception, and speech analysis (e.g., the attack portion of the ADSR envelope model). The concept persists through acoustic measurement conventions, musical notation, and linguistic transcription. Parameters: onset is a boundary marker, not a duration; it pinpoints when a sound's energy crosses a perceptual or physical threshold above the preceding baseline. It operates at the level of individual sound events within a temporal sequence, enabling the segmentation and labeling of temporal structure in audio. [formal: onset | substrate: mind | horizon: a moment | explicit: yes | epoch: 0.01]