First Reflection

The initial sound reflections from nearby surfaces that arrive within 10-30ms of the direct sound.

First reflections (or early reflections) are the initial sound reflections that reach the listener's ears shortly after the direct sound. They typically come from nearby surfaces: side walls, ceiling, floor, and the console/desk surface in studios.

First reflections are acoustically significant because: • They arrive within 10-30 ms of direct sound • The ear integrates them with direct sound (precedence effect) • They cause comb filtering: constructive and destructive interference with direct sound • They affect stereo imaging and phantom center stability

In studio control rooms, the "reflection-free zone" approach treats first reflection points with absorption to create a cleaner monitoring environment. First reflection points can be found using the "mirror method": if you can see the speaker in a mirror placed on the wall, that spot is a first reflection point.

Alternative approaches use diffusion at first reflection points to scatter the energy and reduce comb filtering without completely deadening the room.

Practical Example

Speaker 2m from side wall, listener 3m from speaker

Direct path: 3m. Reflected path: ~4m. Time difference: ~3ms

At 3ms delay, comb filtering creates a notch around 170 Hz. Treating this reflection point eliminates the coloration.

Glossar · Diffusor-Designer

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