But I think there's an even better way to implement it: background audio. Because 1) you can have multiple distinct sounds (eg. waves, cat meowing, bird chirping, windchimes, etc...), and 2) with modern 3D effects, you can subtley tweak the audio in many different ways, to play with what sort of filter would best convey how strong something has gotten. (eg. a cat meowing in the next room over, could mean something different from the cat meowing in the next room over where there's a block of styrofoam in between, could mean something different from the cat meowing
Another benefit is that it's cheaper than the orb, because it needs no additional hardware. It's a win/win!
Software: