Direct acoustic wave

Professional Definition

A direct sound wave is a wave that reaches the observation point (listener or microphone) by the shortest possible route directly from the source.

It is a wave that has not encountered any obstacles along the way, so it has not been reflected, refracted, or scattered. In an ideal free field, for example in an anechoic chamber, only the direct wave occurs. Its sound pressure level decreases systematically with distance – for a point source, the loudness drops by 6 dB for every doubling of distance.

Acoustics in Simple Words

Imagine standing in a dark room, and your friend is shining a flashlight straight at you. The light that comes directly into your eyes from the bulb is akin to a direct wave.

If your friend aimed the flashlight at a mirror or a white wall, and you saw only a glow – those would be reflected waves. The direct wave travels "as the crow flies," in a straight line from the speaker or instrument straight to your ear.

This is why you can point with your finger to a direction with your eyes closed: "there stands the guitarist." It reaches us first (it is the fastest because it has the shortest path), carrying the clearest information about the location of the sound source.

Summary

• Shortest Path: Sound that arrives without interaction with the floor, ceiling, or walls.

• Localization: A key element that allows the brain to precisely determine where the sound is coming from.

• Clarity: It serves as a reference point for assessing sound quality – the more direct wave relative to the reverberation, the clearer the sound (e.g., speech).