Likely it's not a virus.
You could run a short test to see if it is a focus issue, where the window you are working in loses focus. When that happens, striking any key (typing in Word for example) will result in multiple beeps until the cursor is moved and clicked onto the Word document you were working on.
Test:
- Open a new word document and type a few words
- While the word document is still open, open a browser and resume typing
Fix requires you click on the window you wish to work on, i.e., the word document. The word document lost focus when you opened the browser window. Hence the beeps you've been hearing?