I haven't dealt with doctors, but I did have to interview some university professors about religious conditions in France in the 1800's, and I can tell you that it went very well, better then I expected.  Most people are happy to talk about their expertise and everyone I dealt with was satisfied with being mentioned in the thank yous.  Some things I learned are to stay local if you can, if you live near a university or hospital that you can get to, try them first.  Any of these places will have a directory online that you can look through and call and make an appointment.  You might have better luck with professionals that teach as well as practice, they are used to answering questions and often have time set aside for students that you can sneak in on.  My biggest piece of advice is to be professional.  Be prepared, know exactly what you want to ask and appreciate the help.  Don't waste their time.  There are some databases online that list registries of experts willing to speak about their field, but I don't know if they require payment or not.  Anyway, all you can do is ask, I know I was surprised by how helpful people were.  Hope that helps a bit.

Erin's advice about staying locally is good, but I'd offer a refocus on "starting" locally rather than staying local.  Out of necessity I have established a number of international contacts and the trick is to find ways to build relationship--easier locally, but do-able remotely given time, effort and the right vehicle(s).  Good luck with your project! 

BTW, I know of a Canadian who has a health system background, is an RN and also was interested in looking at recreationally induced hearing loss ... don't know if such a resource would be helpful or not--or his willingness to share--ut let me know if you want an introduction.  (See how "remote" works?)