Hearing Aid Compatibility - Frequently Asked Questions

When a hearing aid user wishes to use a mobile phone / cordless phone:

1. What is the background to the problem?
With the introduction of digital mobile phones it has become apparent that they can cause interference to a wide range of audio equipment including hearing aids.

Anyone who wears a hearing aid and is considering the purchase of a mobile phone should ensure that their hearing aid and the mobile phone will work together.

Research has shown that some mobile phones cause more interference than others do and that some hearing aids are more susceptible than others to interference from digital mobile phones.

The interference is caused by the type of radio signals that are transmitted from the digital mobile phone being picked up by the hearing aid amplifier. The interference decreases rapidly as the distance between the mobile phone and the hearing aid increases. For this reason there has been no reported problem from the base stations that transmit signals to the mobile phones

There is now an international standard that sets the level of immunity for hearing aids, and all new models of hearing aids will comply with this. This means that users of new hearing aids being used 2 metres or more away from a mobile phone should find any interference reduced to levels low enough to allow their aids to be used with little difficulty. The new products of all EHIMA member companies meet these specifications. However older hearing aids may have problems.

However due to the way signals are transmitted by mobile phones it still may not be possible to use a digital mobile phone in the normal manner with a particular hearing aid. The hearing aid industry is working towards further compatibility standards which aims to allow hearing aid wearers to use mobile phones in combination with their hearing aid as other people do. The mobile phone industry has also responded by supporting research and with the development of specialised hands free accessories (see Question 12).

The problem is becoming more complicated due to the fact that new phones are being introduced that operate on two widely separated frequencies, known as dual band operation. Users will not know which frequency the phone is operating on and while a hearing aid might work satisfactorily with a mobile phone at one frequency it may be unusable at the other frequency.

2. What solutions exist if a hearing aid user suffers from interference from a digital mobile phone?
There are several things that can be done which may improve the situation
1. If possible use the mobile phone on the non-aided ear
2. Try a different mobile phone to check for any improvements (see Question 3).
3. Use a hands free kit (see Question 12). Different accessories can be coupled to the hearing aid by either using the Microphone or T-Coil position
4. Use a different, more immune hearing aid (see Question 5)

3. Will a different mobile phone help?
It has been shown that there can be considerable differences between mobile phones in terms of the interference they cause to a hearing aid wearer. Therefore it is worth trying different mobile phones before you consider changing your hearing aid. At the moment it is still possible to obtain analogue mobile phones and you may wish to consider using these for the time being. However they will disappear from the market in a few years time. You should also consider using a "hands free kit", (see Question 12)

4. What is a dual band phone and will it help?
A dual band phone is one that operates on two separate radio frequencies. The service operator, to provide the best use of the network, automatically changes these frequencies. The problem for the hearing aid user is that they will not know when these changes take place. Consequently their aid may work well with the phone at one frequency but not at the other.

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5. Would a different aid help?
Before thinking of changing your hearing aid it would be worth while to try different mobile phones to see if there is one that is suitable (See Question 3). Some hearing aids have higher levels of immunity to interference than others. In general smaller aids worn in the ear have higher immunity, than those worn behind the ear. It is important for the user to try a new aid with a mobile phone to confirm that it does not cause interference before accepting it. It is also important to remember that the power level of the phone?s transmitter changes with geographic location and therefore the radio signal is likely to be greater in a rural situation than in the centre of a town. The radio frequency that the phone is using may also change if it is a dual band model. The phone should therefore be tested in a range of situations with the hearing aid, as it may not be satisfactory in all conditions of use.

6. Will a hearing aid user have difficulty using a GSM mobile phone?
Most new models of hearing aid reduce the interference from GSM phones to acceptable levels if they are more than 2 metres away. Some are also immune to interference when the phone is brought up to the same ear as the hearing aid. The result depends on the level of immunity designed into the hearing aid and the type of mobile phone. Unfortunately many types of older hearing aids are likely to be susceptible to interference making it very difficult to use a mobile phone.

7. What form does the interference take?
The aid user will hear a buzzing sound, which grows louder as the phone is moved nearer to the aid. Normally the GSM phone will only cause significant interference when it is closer than 2 metres from the hearing aid user.

8. How can the aid user determine whether the GSM phone is the cause of the interference?
To check if the interference is coming from a GSM phone, first check that the hearing aid is not malfunctioning due to acoustic feedback (earmould not fitting properly) or any other reason. Then try moving a mobile phone which is engaged in a call near to the hearing aid and listening for interference.

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9. Does the interference cause any damage to the hearing aid?
No, the hearing aid will return to normal operation when the phone is removed from the vicinity of the hearing aid.

10. Will the interference cause any damage to my hearing?
No. It may cause some discomfort due to the loudness of the sound and its rasping nature but due to the way your hearing aid should be set up it will not damage your hearing.

11 Will using the 'T' positions on the aid overcome the problem?
Not necessarily, indeed some aids are worse on the "T" position. We are not aware of any current mobile phone which has an inductive coupler for use with a hearing aid on the "T" position.
However "hands free" kits (see the question below) may provide the necessary form of coupling. As with all solutions the user should check that the phone, with any attachments, and the hearing aid would work together satisfactorily.

12. What are "hands free kits" and why are they useful?
Hands free kits are devices which plug into the base of a mobile phone and allow the user to speak into a microphone and hear a reply through an earphone or loudspeaker (see Figure 1). The advantage to hearing aid users is that the kit allows the phone to be used away from the ear and the hearing aid, significantly reducing the likely level of interference. In addition inductive coupling can be provided in conjunction with, or in place of, an earphone. Some mobile phone manufacturers are now providing such facilities but you may find that they will only fit certain models in the manufacturer's range.

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13. What is the difference between a digital GSM phone and an analogue phone?
GSM stands for Global System for Mobile communication, and is a cellular radio communications system used in more than 140 countries world-wide including most European countries. GSM phones operate by means of a digital system of radio transmission. The GSM system requires that the radio signal is switched on and off very rapidly (217 times a second) to carry the messages. In analogue phones the radio signal is almost constant. Analogue phones use a similar system to your FM radio and do not generally cause a problem with interference. Analogue phones are likely to be phased out of service within five years in many countries.

14. What is the difference between mobile and cordless phones?
Cordless telephones are designed to operate over short ranges from a fixed base unit that is normally located in the same room or building. By comparison GSM phones are designed to communicate over larger distances to base stations which may be several kilometres away. In Europe the DECT (Digital Enhanced Cordless Telecommunications) type of cordless phones are becoming common in home and office situations. DECT phones use far less power than GSM phones, but employ similar digital techniques.

15. Will using a cordless phone cause any problem with interference?
Cordless phones may work with an analogue radio frequency signal to connect the handset to the base station or use a digital system. Currently many cordless phones use a digital system called DECT. The analogue phones do not generally cause a problem with hearing aids but the DECT system may cause problems in the same way as the GSM mobile phones. Hearing aid users may therefore also experience interference from DECT phones and should check that there are no problems in using the cordless phone before they purchase it.

16. What can be done about the problem of interference if it creates difficulties?
It has to be dealt with in the same way as for mobile phones. See Question 2.

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