How do I play if I'm hearing impaired or don't have a soundcard?

Well, if you think about this logically - you'll work this out for yourself.

This isn't really a game about sound... it's about sight.

How do you know which Didgeridoo has played? By the sound it makes?

No, you can only really tell by watching to see which Didgeridoo "lights" up.

Infact - some people find the didgeridoo sounds distracting and turn off their speakers

so that they can concentrate on just watching to see which didgeridoo plays.