Flutter Echo

A rapid series of echoes caused by sound bouncing between parallel reflective surfaces.

Flutter echo is a distinctive acoustic defect characterized by a rapid, repetitive "buzzing" or "ringing" sound. It occurs when sound bounces back and forth between two parallel, reflective surfaces, creating a series of closely spaced echoes.

Flutter echo is most noticeable with transient sounds (claps, clicks, consonants) and typically occurs when: • Two parallel surfaces are both highly reflective • The surfaces are relatively close together (2-8 meters typical) • There's minimal absorption or diffusion to break up the reflection pattern

The flutter rate depends on the distance between surfaces. For walls 4 meters apart, reflections arrive every 23 milliseconds (0.023s), creating a distinct "twanging" quality.

Flutter echo degrades speech intelligibility and musical clarity. The solution is to treat at least one of the parallel surfaces with absorption or diffusion. You don't need to treat both.

Practical Example

Two parallel walls 4 meters apart

Time between reflections: 2 × 4 / 343 = 23.3 ms (about 43 reflections per second)

This creates a "buzz" at roughly 43 Hz. Adding absorption or diffusion to one wall eliminates the flutter.

Glosario · Diseñador de Difusores

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