Apple was granted a new patent (filed in 2015) that details an audio device that uses a diaphragm made from a graphene-enhanced composite material. Apple's graphene membrane can be used in a speaker, microphone or headphone device. The patent specifically includes an image of an iPhone device as an example application.
Apple explains that as devices become smaller and lighter, it is ever more challenging to provide high quality audio using conventional materials - and graphene may improve the mechanical response of the audio device. In addition, in some cases, the use of graphene or graphene flake materials may reduce or eliminate the need for additional external damping.