if US: I got an ADA but it didn't help me from the sighs, skepticism and disinterest. I still got railroaded out of the job. luckily have a new job no talking woo. If you want the job but aren't comfortable with the new responsibility you can even ask you primary care for an ADA letter and try it out. some companies really don't like when you ask for a reasonable accommodation of any kind so consider the company and the HR people. my manager is the one who wanted me out, just the sound of my voice. but if the speaking isn't a new position/title I don't see how they could just push that kind of expectation on you, someone they know has a speech disability. people do it somehow with a stutter every day, beyond me but hopefully you have more luck than me!! would visual aids like a slide show or crowd work? ( working on making people uncomfortable right back and calling on them to raise their hands and ask/answer YOUR questions.)