The sound you hear from a single source, the audio source is loud or continuous basis. Best sound heard from two sources that sound source has a slightly different frequencies are louder and rhythmic alternating fixed.
Sound from sound source to a single source. Noise is uniformly continuous. The sound from the sound source, two sources with slightly different frequencies are loud and gradually turns into a steady rhythm.
The sound from the sound source single source. Is the noise steadily. The sound from the sound source, two sources with a frequency slightly different is the noise, and then switch to a rhythm.