Artist Brian Davies
About the science:
The simplified rule. If two similar (but not identical) frequencies exist together then two more frequencies are formed.
1. The sum of the first two and
2. The difference between them. We are only interested in the latter and we call it a “beat note”.
For folks that play stringed instruments you are familiar with beat notes from tuning. For the others get someone to whistle and hold a note and you try to perfectly match their note, you will hear a beat note as you get close to the same frequency.
I used a 20 litre pail, a heavy plastic bag, a speaker, some crystals of various sizes and two audio frequency generators (one is my guitar tuner) to make it possible to see as well as hear the beat. They make patterns that are unique to the two original tones and the beat note.
The boogie was just for fun.