A digital cell phone (sometimes called a "digital wireless phone" not only process the sound digitally, they actually receive and transmit the audio as a digital signal via radio waves. For hearing aid wearers, many of these digital wireless cellphones have a tremendous disadvantage because some interfere with hearing aids ... they cause a loud buzzing sound to be emitted by the aid, making it impossible to hear the voice being transmitted by the phone. You don't even have to be using the phone yourself to hear the interference. People wearing hearing aids who are near someone else using a digital wireless cellphone can hear the buzzing.
SHHH has worked with legislators and manufacturers in an attempt to eliminate the interference caused by digital wireless cellphones, and many new phones are much improved, but the effort continues.
Another type of phone which is digital is the digital phone. It also presents certain problems for people with a hearing loss.