Hello Benny, Sara,

I found 哑子 yǎzǐ for mute.
Here mute means a person whos is not able to speak
by lack of vocal cords or tongue (physically mute that is)
If however you mean someone who cannot speak because he hasn’t learned to speak that would be
笨蛋 (a stupid egg, or now I come to think of it someone who acts as if he has just left his egg,
meaning still behaving lik a child).
Here his disabillity is not physical but mental.

哑子是不会说话的人因为没有舌头或是声带。笨蛋的人是会说话的人但是他没有头脑！:-)

Then there are mute lettrs, letters written but not spoken, the b in dumb is mute and so is the b in comb, this is I believe called 默音字母
(black sound letter of the alphabet) ….

I hope this might share some light on this subject.

万事如意

陆蓝克