When did your voice fully mature? I'm 17, and when I try to slow down and deepen my voice a bit, it gets sort of shakey. Is this my natural voice (like Jack Nicholson?) or is it something that'll go away if my voice is still maturing?

Hey bro,
Im 18 and I dont think it really matters what your natural pitch of voice is. What matterns is the way you control it.

At first youve been spending 17 years of your life speaking in one way nows the time to practive speaking with your diaphragm, place your hand on your chest and keep trying differnt ways to talk untill you start talking with a more resinating voice.

At first it will be shaky but thats only beacuse its a under worked muscle group, you just need to do it more and more and eventually you may only be able to speak that way.

I started with deepening my voice when i laugh. A more roaring chuckle i always finds helps establish alphaness especially if you can master that deep laugh over alot of noise.

Deep voice means more testosterone = more sexual attraction from the ladies.

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Ratio theroy...