Audio codec, weird helicopter sound, potential data error. (WM8731)

Hey everyone,

Hopefully somebody has experienced something like this before and point 
me in the right direction.

I have a Wolfsom WM8731 connected to an STM32F405. I am able to start 
the codec however once I start transferring data over DMA to it there's 
a weird helicopter sound.

I can hear what is meant to be the data very faintly underneath the 
helicopter sound.

Does this sound familiar to anyone? (See attached audio file)