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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. 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.
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.
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.
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.