Have you re-booted the computer? Does this only happen when you have a web page open?

It is no doubt a pop up or an advert running with audio or a advert clip, that you are unaware of.

thanks for that info. I do have firefox with the appropriate add ons so I shouldn't be getting advertisements or pop-ups. But I suppose it is possible. I am not hearing anything today so hopefully it was temporary whatever it was. I will reboot to make sure.

Abbey

fwiw.
My dad was a ham radio guy.
His radio voice at times would broadcast on my pc speakers. Not loud like a normal volume would be, best I can remember.
I never could stop it. Tried different simple things. But it really wasn't annoying so I didn't go crazy trying to eliminate it.

See any radio towers on neighbor homes ?

I have a pair of Acer USB powered speakers that eventually I learned to keep my cell phone away from. They aren't voices though, just squealing noises whenever the phone "calls home?".

Have you scanned for malware to rule out that possibility?

Abbey if you are still here this is a shot in the dark.

With your WiFi, how close is the router to your computer?

I ask as I have a 4G LTE provider with my router on top of the bookcase for my computer desk. The left speaker use to be right next to it. I had to move the speaker down onto the floor in the rear of the leg-well due to some mighty strange noises coming from the speaker. Nothing unusual with the right speaker, and I never had the concern with a 3G system. Maybe, just maybe.

DA