Interference of Sound – Two Tuning Forks

Two identical tuning forks are struck one after the other. The sound waves produced by both tuning forks interfere with each other as they travel through space.

When the crest of one wave overlaps with the crest of the other wave, or the troughs of two waves meet, the two waves reinforce one another, and the sound becomes louder.

If a crest of one wave meets a trough of another wave, the waves cancel each other out, and the sound in this section ebbs away.

Let us now consider a specific phenomenon that occurs on an imaginary line connecting two tuning forks. Two sound waves travelling in opposite directions interfere with each other, creating a so-called “standing wave”. The points where the two sound waves always cancel each other out are called nodes, and they are one-half wavelength apart.

Antinodes, where both sound waves reach maximum amplitude, form midway between the nodes. These nodes are starting points of nodal lines on the plane shown here, and of nodal surfaces in space. The sound waves cancel each other out on every nodal surface in space.