Interferentie: padlengtes

Imagine two speakers being fed by the same sound source of a single frequency. In this case, the two waves have no phase difference at the speakers.

Recall that sound waves are traveling waves involving both space and time coordinates. So, at a point P, the distance traveled by the two waves differs.

The waves are expressed in terms of the traveled paths. A phase difference has been introduced simply because of the difference in path lengths, called the path difference.

If the path difference is an integral multiple of the wavelength, the waves interfere constructively. If it is an integral multiple of the half-wavelength, they interfere destructively. For this reason, when two crests or two troughs meet, they interfere constructively, while the crests and troughs interfere destructively.

At points other than the crests and troughs, the amplitude is intermediate.

If the speakers were fed by different sources with a fluctuating phase difference, the interference pattern would change rapidly and be washed out.