The audio always changes volume. It goes quiet and loud.

If the audio is changing volume for you, this is probably caused by the Windows Audio priorities. 
The issue is, that another application can claim priority over Hyper and cause Hyper to lower its volume. 
A common culprit is Steam running in the system tray. Try closing any background applications you have running. It is likely one of them is interfering with Hyper's background audio capability.

Feedback and Knowledge Base