Cell phones and hearing aids were the topic of one of the most commented upon blog postings at About Deafness/HOH. I do not have hearing aids myself, so I did some research to see what I could learn about hearing aids and cell phones.
Problems
Cell phones can cause radio frequency interference, making a buzzing noise or feedback sound that the hearing aid user hears. This can make it difficult to hear and understand speech.
Technology
The Federal Communications Commission (FCC) requires cell phone makers to make phones compatible with hearing aids. The Hearing Aid Compatibility Act of 1988 was modified by FCC in 2003, to require accessibility for cell phones.
Full details are on the FCC website. Under the updated regulations, manufacturers must provide hearing aid-compatible handsets.
Accessibility
Some hearing aids are able to handle cell phones, and some cell phones have improved hearing aid compatibility. In the blog comment thread, About visitors recommended brands of hearing aids and cell phones. In addition, there are hands-free hearing aid compatible accessories, and adaptor devices/boots for hearing aids. Hearing aids may also have telecoils (also known as t-switches) to aid in hearing the sound from a cell phone. Telecoils may be built-in or optional.