preechoes

Preechoes are a phenomenon observed in acoustics and audio signal processing. They refer to faint acoustic signals that precede the main sound event, often a spoken word or a musical note. These preechoes are typically much quieter than the primary sound and can be difficult to detect without specialized equipment or by listening intently in a quiet environment. The exact nature and origin of preechoes can vary depending on the acoustic space and the source of the sound.

In some cases, preechoes are thought to be caused by the early reflections of sound off surfaces in the environment. As a sound wave propagates, it bounces off walls, ceilings, and other objects, and some of these reflections can arrive at the listener's ear slightly before the direct sound. These early reflections, if faint enough, can be perceived as preechoes. Another theory suggests that preechoes can arise from the physical mechanisms of sound production itself, particularly in the excitation of resonant structures.

The presence of preechoes can have subtle effects on the perceived quality of sound. While often inaudible, they can sometimes contribute to a sense of spaciousness or realism in an audio recording. Conversely, if too prominent or distorted, they might be perceived as an unwanted artifact. Understanding preechoes is relevant in fields such as architectural acoustics, audio engineering, and the study of psychoacoustics, where the precise timing and perception of sound are critical.