I can't give you an answer, but I would start checking the Task Manager, Process tab to see if any process is "cutting in" at these times.

You can open the Task Manager by
a) Pressing CTRL+ALT+DEL together, or
b) Right click the Taskbar then select Task Manager.

There are a number of tabs and the Processes tab shows what processes are currently running in the background. This is useful for investigating what is going on under the hood. The Processes window has a number of columns, and yours should show a column called CPU. If it does not, goto View > Select Columns, and select "CPU Usage".

If you click each column header, the listing will change to order itself correspondingly. For this test you need the processes using the most CPU usage to be listed at the top, so click the CPU column twice.

Why use this?

If you are listening to audio you don't need anything else on the display screen, so watching the Task Manager doesn't get in the way of anything you are doing. Play your audio files, and watch out for any change in the Processes listing when the audio falters. That may at least point you to some process that is interrupting the CPU.

I don't guarantee it will find anything, but it is a start.