High pitch noise coming from left speaker when I hold my hand over it

Hello

I just realized today while fiddling with Skype that when I hold cover the left speaker of my macbook pro with my hand it makes a high pitched noise. Only happens when I cover the left speaker with an object.

Anyone know why this happens? Is this something that can be fixed or do i need to go back to the shop?

Thanks in advance.

i returned my uni MBP 2 times for speaker rattling issues and such

Ok I figured out that if the mic is off, this doesnt happen.

Is there a way to stop this even if the mic is on?

Seems like a hardware issue.