Problem with voice speaker

Hello everybody. I have a problem, and I would need your help if possible!

I am having some troubles with voice speaker. When I am speaking with somebody, the volume of the speaker sounds very low. I have seen there exists some mod to increase music speaker, but I have not found anything relating my problem.

Does anybody know if there exists any solution (registry modification, mod, etc…) to solve this problem?

Thank you very much!