Roger Mills wrote:

My W10/64 Pro desktop computer emits a strange squawking noise from time
to time
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.

I don't recognise the sound, but if you right click the speaker icon in
the tray after it's done it, and go to volume mixer, it usually shows
individual sliders for any apps that have recently played sounds, so
look for apps other than the "usual" such as browsers and media players.