First, a 440hz tone will play on the LEFT side. Then, it will stop and play a 440hz tone on the RIGHT side. This is for testing which side is which, and if your stereo system is working properly.
I was testing some vstis and vsts and recorded these samples. Some ausition magic added. Synth passed to heavy flanger. Loopable for 120 bpm if you know what to do (i do not).
Our town was testing the sewers somehow using audio tones to measure something. Maybe resonant frequency or something like that. It sounded vey musical since they were using 3 tones per octave, like a scale based on an augmented fifth chord.