Acoustic pole of direct wave

Professional Definition

The area of the acoustic field inside, near the source, which can be considered as a free acoustic field.

In engineering terms, it is the zone where the sound pressure level is determined almost exclusively by the wave traveling directly from the source to the receiver. In this area, the influence of waves reflected from walls, ceilings, or floors is negligible in terms of energy. For a point source in the direct field, the inverse square law applies, meaning a decrease in sound level of 6 dB with every doubling of distance.

Acoustics in Simple Words

Imagine you are standing in a dark room and someone is shining a flashlight directly into your eyes from half a meter away. You can only see the dazzling light of the bulb – this represents the direct wave. You do not yet notice the light reflected from the walls, because the direct light is too strong. In acoustics, it is similar: when in the direct field, you hear the "pure" sound of the instrument or speaker, without the "interferences" resulting from echoes or the reverberation of the room. It is the moment when the sound is most intimate and precise.

Summary

The acoustic field of the direct wave is the zone of dominance of the source over the room. Its range ends at a point called the limiting distance, where the energy of the reflected waves equals the energy of the direct wave.