MacBook Pro audio distortion

My very new MacBook Pro is having sporadic audio distortion issues. This seems to only be affecting the internal audio - laptop speakers and headphone output. I don't get the issue with external audio hardware. A restart fixes it... until the next time. I initally tried a PRAM reset and then a re-install of the OS - not a full clean install though - I'd rather avoid that if poss since I have around 900GB of data on this laptop that would need re-installing. Any advice on how I might fix this issue or do I need to drop the MBP into my local Apple Service centre?