Why does the audio pitch up slightly on first call?

Why is it that when my audio is first called it is pitched up slightly?

is it an error in the engine's audio function?

& can it be fixed?

The only reason this should happen is because of the Dppler effect.

http://unity3d.com/support/documentation/Components/class-AudioManager.html

http://unity3d.com/support/documentation/Components/class-AudioSource.html