Introduction to mobile phones - Part 2

Presented by Scott Kelley

With improvements in both telephone technology and hearing aid technology, more people with hearing loss are able to use mobile (cell) phones. Here's Motorola's Scott Kelley with great information on mobile phones and how to choose one.

This is part two of two parts.

For more coverage of this great convention, please point your browser to http://www.hearinglossweb.com/res/hlorg/alda/cn/2006/2006.htm

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Part One

Wireless phones can interfere with some hearing aids and cochlear implants, causing an annoying or even painful buzzing. There are two types of interference. One is the radio frequency (RF) interference when my phone is talking to the tower. The second type is baseband (0-5kHz) interference. There are all kinds of components in the phone doing all kinds of things. People with normal hearing can't hear them, but sometimes hearing aids pick them up. They can be particularly loud when people are using their telecoils.

Q. Are we talking about things specific to the cell phone, or other things in the environment?
A. We're talking about signals produced by the cell phone.

Q. Can you shield against this interference?
A. Yes, and we'll talk more about it later.

Q. Is the buzzing sound similar to the buzz caused by fluorescent lights?
A. Different types of interference produce different kinds of buzzing. The fluorescent light ballast produces a 60 Hz signal. The backlight of some phones produces 50 Hz signals, which are similar to the 60 Hz signal. Keypads are also notorious for producing interference.

If you hear a buzz when you hold the phone up to your ear, and it goes away when you move the phone away from your ear, it's caused by your phone. Phones typically don't cause interference when they're more than a foot or so away from your hearing aid.

Something like a backlight may be on for 10 seconds. So when you use your phone, the interference may be on for a while and then go away.

When there is interference there is a source and a receiver. And the interference is never the fault of just one of them. Hearing aids, for example, can be shielded to help remove interference. Capacitors on the inpuit circuitry of your Tcoil can reduce the buzzing, so shielding and filtering are two ways to immunize hearing aids from interference.

Hearing Aid Compatibility (HAC) is a systems compatibility issue, and both the telephone industry and the hearing aid industry must work to make the problem go away.

Hearing aids produced in the last 18 months or 2 years tend to be shielded and filtered, so those are less susceptible to interference.

C. When you get your hearing aid refurbished, you can ask them to refurbish your Tcoil, as well. That might help with preventing interference. You typically have to ask to have your Tcoil included, or they normally won't do it.

Measuring individual devices to predict system compatibility - ANSI C63.19 is the standard. The idea was to allow you to test a hearing aid and a cell phone separately and be able to predict if they will work together.

The standard was released in 2001. It discusses hearing aid immunity, which is how well the hearing aid blocks RF and baseband signals. It also discusses telephone immunity, which is how well the phone blocks the signals. Both hearing aids and phones are given ratings from one to four, with higher numbers being better. In general if the sum of the ratings for a hearing aid and a phone is five or higher, the performance of the phone with the hearing aid should be acceptable.

The testing has become quite complex, with fixtures that allow the phone and hearing aid to be tested under very precise conditions.

The FCC HAC mandate specifies that a certain number of phones from each manufacturer and for each digital language must be HAC.

C. I go to the phone stores and I find that the people who work there really don't know much about which phones work well for people with hearing loss.
A. We're not a carrier, so we aren't directly involved in this. And you have to understand that these stores are often manned by 16 year olds who are working there for the summer, and they don't have a clue about how to help you. But I also understand that it's very frustrating for you. One thing we're doing is coming up with a DVD to train the people who work in the stores. We hope that helps.

The FCC is the governing body for wireless phones. They looked at the standard that we talked about, and said that they don't regulate hearing aids, but they do regulate cell phones. So they took the cell portion and mandated that you have to have a certain number of phones that rate M3 or M4 and rate T3 or T4. The M is the immunity rating when the hearing aid is used with the microphone, and the T is the immunity rating when the hearing aid is used with the telecoil.

What's missing from much of this discussion is the hearing aid. The hearing aid ratings aren't nearly as far along as the phone ratings. Most people have no idea how their hearing aid is rated. To find out how the system will perform, you need to add the cell phone number to the hearing aid number to get a system score. You can't do that if you don't know how your hearing aid performs.

Q. Can we call the CI companies and ask them what their score is.
A. The standard is really for hearing aids, and I don't know if it really applies to CIs. Because of the similarities between the functions, I think they may apply to CIs, but I really don't know.

The moral of the story is that you're stuck with the hearing aid or CI aid you have. So your best bet is to go to a phone store and try a phone, and if that doesn't work, try another one. And if the store won't let you do that, go to a different store.

Remember that this is a system issue. We think it's a little strange that when your $50 phone interferes with your $5000 hearing aids, you get upset about the $50 phone. We think that the hearing aid manufacturers have some responsibility here, as well, even if the FCC doesn't mandate it.