I can't tell what gender my mallards are, could anyone please help me identify it?

[AmbersOfNimbus]

So I've got two mallards. I'm almost sure they're male and females, however I can't tell which is which. One has a more high pitched, I'd say pippy kind of quack. While the other has a more deeper, almost raspy seeming one. I'd normally assume that means the first is female and the latter would be male, however I'm just wanting to be 100% sure.
These are the pictures I took last week. I can get new ones if needed. I got the ducks on the 29th of February.

 

[Isaac 0]

The raspy one is a male, the quacker is a female.

 

[AmbersOfNimbus]

The raspy one is a male, the quacker is a female.

I suspected that, thank you!