By Geoff Adams-Spink
Age & disability correspondent, BBC News
Future hearing aids
It is estimated that almost 9m people in the UK have some sort of hearing loss.
There is no shortage of technology that promises to correct - partially or in full - a particular problem.
But how can people be sure that what they are buying really can do "what it says on the tin"?
This was the subject of a recent "show and tell" session held by the Royal National Institute for Deaf people (RNID) in London.
The Institute has a team of experts whose job is to test new products and to give advice to manufacturers so that they can produce items that are well-designed and which bring real benefits to people with hearing impairments.
The RNID's evaluation team will look at everything from smoke alarms to alarm clocks and video phones.
It sees its role as being the voice of the user whose needs should be taken into account from the outset.
Often products - mobile handsets for example - are tested in batches in order to provide some sort of comparison.
After initial safety testing, products are submitted to close scrutiny under laboratory conditions to ensure that the manufacturer's claims of performance are true.
One of the testing devices - KEMAR or Knowles Electronics Manikin for Acoustic Research - is an attempt to simulate a human head and how it processes sound.
It has soft, plastic ears and the same dimensions as an average adult male.
Products are also evaluated by teams of experts alongside ordinary users, and the RNID is keen to hear from deaf and hard-of-hearing people who are willing to take part in various trials.
The RNID also works closely with the British Standards Institute (BSI).
For example, it has developed the standard for smoke alarms for use by deaf people.
But in order to do so, it was first of all necessary to establish the strength of vibration required to wake someone up.
The organisation worked with Exeter University and Papworth Hospital in order to provide the necessary data.
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