earlyreflection

Early reflection refers to the first set of reflected sound waves that reach a listener after the direct sound. These reflections originate from surfaces such as walls, ceilings, floors, and objects within a room and generally arrive within roughly the first 80 milliseconds after the direct sound, with the earliest arrivals occurring in the first tens of milliseconds.

These reflections contribute to the perceived size and character of a space and provide localization cues that help identify the direction of a sound source. Unlike late reflections, which form a diffuse reverberant tail, early reflections arrive with distinct times and amplitudes, influencing timbre, brightness, and intelligibility, particularly for speech and music.

Perceptually, the precedence effect describes how listeners tend to localize sounds to the first-arriving reflection when a delayed copy is present; only when the delay becomes sufficiently large do additional arrivals begin to affect perception and may produce echoes.

In acoustical design and measurement, early reflections are managed to achieve the desired balance between clarity and liveliness. Architects and engineers manipulate surface treatments—absorption, diffusion, and reflection—to optimize for the room’s intended use, whether for speech, music, or recording. In room impulse response analysis, early reflections are often treated as a finite set of discrete bounces, while later energy forms the diffuse reverberant tail.

Applications extend to digital reverbs and acoustic simulations, where modeling early reflections helps recreate natural spatial impressions, as well as to headphone and loudspeaker design to preserve accurate localization cues.