I installed the game on windows 8.1 and the sound effects is terrible.
Whenever the bus arrives, the SFX is like multiple noises one beat after the other.

The FAQ mentions something about changing the graphic mode, but I have no issues wth the graphics, just the sound.
Also, what would be the recommended graphics mode if I had to change it?

Any ideas?

Thanks

Note that the sounds gets worse at SVGA (?) mode (when I press R)

Maybe increase the cycles in DOSbox in small steps until your emulation works better? You need to hit a sweet spot and this is unique on every computer.