Who do you plan to send the files to? It absolutely needs to be cleared by your university ethics committee unless the participants actually agreed to have their data seen/listened to beyond the research team. I don't know if you're in the UK, but if so, look up the Data Protection Act - there should be a summary. Also, maybe your ethics committee can advise. Maybe it is OK as long as the participants cannot be identified. It is personal data though, so if it wasn't stated on the participant information sheet/consent form...