As a member of Chorale, I have to sing nearly everyday. But until now I never realized how much singing has to do with physics. For instance, if someone wants to sing louder, they must sing at a higher amplitude and vice versa. Similarly, when someone sings at a higher pitch, it is because they have a higher frequency (frequency is the number of waves that pass a fixed place in a given amount of time). Finally, since all sound waves are mechanical waves, they require a medium if they are to be heard. This is why you can't hear anything in space.