POP noise is driving me insane

About every fifteen seconds, avast makes a pop noise as though it was about to show a popup message. No message is ever displayed. A scan shows no problems. My real time shields show 0/0 on Mail, P2P, IM, and Script, but 158/0 on behaviour, 5500/0 for File System, 39000/0 Network, and 32000/0 Web Shield. I’ve looked through every menu tab and can’t find any ‘warning’ about anything anywhere. What the hell is avast trying to tell me with these noises, and why doesn’t it actually tell me what’s happening rather than just make a noise???
I know I can disable sounds from Settings, but that isn’t really the point - if something is wrong I want to know about it, but a ‘pop’ is a very long way from a useful way of communicating with me!

I have had this issue when a Sound Blaster is failing. Disable avast! sounds to verify if avast! J.R.