Gentleman cho'gath voice too tune down

Don't know if it's a bug or not, but as I tried the gentleman cho'gath skinI got with capsule, it seems that his voice have a lower volume than all the other champ/skin.

It's kinda disturbing because I can't really understand his line dispise knowing that he is speaking (only some word are understandable if there is nothing dying/casting/atacking in the area around the champ)

don't know if this will help but I play the french version of the game, if by chance volume are different for all voiceover