My W10/64 Pro desktop computer emits a strange squawking noise from time
to time - typically several times a day but sometimes several times in
quick succession.

Each instance is short and sharp, and lasts about 300mS. It is
definitely coming through the audio system rather than being (say) a
disk bearing because its volume depends on the volume control setting,
and I have been able to record it by setting the recording input as
"Stereo Mix".

You can hear it he
https://app.box.com/s/0gtq2lg1eti3z3xfiw898i2b65piq6sp and you can see
the waveform he
https://app.box.com/s/2tewwkwnlqb8uiwiq9glz101rvg4pc4b

I assume that some application or other is trying to tell me something,
but it's never accompanied by any message or notification on the screen,
and I can't find anything in the error logs. In addition, I can't find
any system sound which sounds like this.

I shall be most grateful if someone can put me put me out of my misery
and tell me what's likely to be causing it.
--
Cheers,
Roger