It's your computer, I'm afraid. Couple of options:
1. Turn your computer off an on again. Sounds stupid, I know, but it solves 90% of reported issues.
2. Might be a headphone thing, weirdly. If you have headphones, try running the game with headphones plugged in and headphones unplugged. One of those might work.
Lastly, something screwy may be going on with your GPU so you can try changing the renderer. You can do this by:
- Holding down Shift while starting Ren'Py, or pressing Shift+G once Ren'Py has started.
- From the "Graphics Acceleration" menu that appears, choose the renderer to use.
- Choose "Quit", then restart Ren'Py.
Hope that helps!