Generating security metal detector sounds - how?

[igendel]

Hi,

I'm in the process of designing the electronics for a toy of sorts, and the client suddenly decides he wants it to also make the familiar scanning sounds of metal detectors, like the audio in this:


That video has two kinds of sound, 0:00-0:08 and 0:09-0:18. Either would be fine, and it's not supposed to respond to actual metal or any other input. The catch is that I need to produce the sound using an 8-bit MCU and a piezo element (or a very small speaker), because I already have those in the system and there's very little room for other components.

Looking at the waveforms with non-expert eye, it seems there's a lot of amplitude changes:

Short, rapidly-decaying clicks with variable distances


Some kind of high-pitched slide-whistle AM signal?


So, how can I go about generating these or similar sounds? Can it be done with the aid of a reasonably small analog circuit of some kind? All the metal-detector-related circuits I could find on Google are for actually detecting metal, not for sound...

Thanks!

[igendel]

For future generations reading this...
I discovered that outputting a square wave to a speaker, from say 1KHz to 8KHz and back, in 100Hz steps, ~4ms for each frequency, gives a nice "sliding" sound effect similar to that of the metal detector. Still requires work but it's a start