looking for voice amplification experts

My brother, David W Oaks, became a tetra-plegic as the result of an accident (complete C6/7 break) he suffered in 2012. He is a big fan of Apple products owning both an iPhone and an iPad. Before his accident he was a paid professional public speaker on the topic of Human Rights in Mental Health. A side effect of the recovery process included an injury to one of his vocal cords. David is eager to hit the road again as a paid professional public speaker. He is dealing with a number of challenges starting with the effective use of his iPhone (currently a iPhone 5s with a iPhone 6s expected in November). He is trying to assemble a team of experts who could help him master the topic of voice amplification and hopefully push his iPhone to the limit. A slide pack with links to youtube videos showing accessibility challenges faced by David when he tries to make or receive a phone call (using Assistive touch) on his iPhone as well as the extensions he wants to explore can be viewed on Docs.com at this link: Http://tinyurl.com/ProjectAmplifyUs.