Reverberation

Reverberation is the persistence of sound in an environment after the original source has ceased, produced by the multitude of reflections from walls, ceilings, and other surfaces. These reflections overlap and decay over time, giving a sense of space and ambiance. Reverberation is not a single echo; rather, it is a dense series of reflections that blend together, especially in rooms with hard, flat surfaces.

Physical properties: The rate at which reverberation dissipates is described by the reverberation time, RT60, the time required for sound to decay by 60 decibels. This time depends on room volume, surface absorption, and geometry. Materials with high absorption (carpets, curtains) shorten RT60, while reflective surfaces prolong it. A commonly used estimate is Sabine's formula: RT60 = 0.161 V / A, where V is volume in cubic meters and A is total absorption in sabins (A = sum α_i S_i).

Impact and control: Reverberation can enhance music and speech in appropriate spaces but excessive reverberation reduces intelligibility. Architects and acousticians modify RT60 and spatial character using absorptive panels, diffusers, and strategic geometry. Small rooms typically require more absorption, while large halls may use architectural features to distribute reflections.

In recording and playback, reverberation is simulated using electronic or digital reverbs. Convolution reverbs use impulse responses captured from real spaces; algorithmic reverbs generate reflections mathematically. Applications include music production, film audio, and virtual environments.