1) Check The Game Settings For Inner Tube.

Have Cygnet open, Select Inner Tube

Click on Settings at the top of the Inner Tube Window
Click on Game Settings

Change Game Type:
Feedback: Standard-Speed, Fog & Music

Music Feedback: Increase Volume (may be set to no music)
Engine sound: Quiet (or normal)


2) If Check The Volume Mixer sound sliders and/or see if  Innertube is Muted.

Right Click on Windows Volume ( bottom right hand corner of the screen next to the clock)
Click on Volume mixer raise master volume slider.
Or Slide the bottom slider to the right to see all Application Volume Controls.
make sure the volume is raised up and not muted.