The NYT has an interesting article that discusses a hearing aid technology that has been around a while but is becoming more widespread: Telecoil.
As the article explains:
The basic technology, called an induction loop, has been around for decades as a means of relaying signals from a telephone to a tiny receiver called a telecoil, or t-coil, that can be attached to a hearing aid. As telecoils became standard parts of hearing aids in Britain and Scandinavia, they were also used to receive signals from loops connected to microphones in halls, stores, taxicabs and a host of other places.
People in the United States have been slower to adopt the technology because telecoils were traditionally sold as an optional accessory, at an extra cost of about $50, instead of being included automatically with a hearing aid. But today telecoils are built into two-thirds of the hearing aids on the market as well as in all cochlear implants, so there is a growing number of people able to benefit from loops.
The bottom line is the installation of these telecoils are truly good for business. Someone who has trouble hearing is more likely to visit a place where they can enjoy the performance. It's interesting to note, that they are even being installed in train station fare booths where hearing aids don't work very well due to the noise. As more businesses see the benefits perhaps more businesses such as museums and theaters will make this technology more readily available.