How does the sound waves effect the pitch of sound?

It can be done by moving the sound source quickly towards the observer (or the observer towards the sound), like a siren on a speeding train, and is known as the Doppler effect. See related link.

The pitch of a sound wave is a subjective quantity that depends on the objective quantity frequency.

Pitch is determined by the frequency of the wave; intensity (loudness) is determined by the wave's amplitude.The vibrating source moves in some kind of periodic way, and this periodic motion will...

Its' frequency.