To complement Theodoric's suggestion, regarding the materials of construction, you could try a google on "rare earth magnet headphone" & "mylar headphone", for a start and see where that leads you.
Also try looking at technical specifications in magazines, or sites which sell headphones and google on anything that looks interesting.
Towny is right about emailing not being viable for stuff like this, - hope you have some luck with the phone calls - my suggestion is to try the "customer care" number - for example you could ask if they have any "company statement" on ergonomics - (btw imo, pose as a potential buyer, not a student looking for an easy way out

)
- any project which shows evidence of using as many sources of information, as possible, will impress!
- remember to quote your source of information - and if you build a bibliography, even better!

that sounds pompous & patronising, sorry, but I wish my son had followed my advice for his project - he might have passed
Gaz