I had something similar happening to some clients, one person had a cat meow, another a dog bark, along with many other random sounds. It took a while to figure out I ran, eset, spybot, malwarebytes and nothing found it. But I ran some research and found that there was many forms of this happening with all different solutions the one that worked for me was a folder that was created under the C:\Windows\Syswow32. This folder is not supposed to be there and contained the files that were causing the random sounds. I deleted that on all the computers that were having the issue and have not seen it since. The one thing that all computers had in common was an email that they had sent around. I have been closely monitoring the computers since with the mentioned AV solutions and have not seen a problem. Hope this helps.