Feb 262018

Just in case anyone is interested in helping Chris with this project in Zimbabwe



My name is Chris Prescott and I am a retired Paediatric ENT surgeon. I spent most of my working life at the Red Cross War Memorial Children’s Hospital in Cape Town. Since my retirement I have spent time trying to encourage the development of ENT and Hearing services in Zimbabwe – where I was brought up – and the other countries in Central Africa, assisting the few local colleagues struggling to cope in these countries.

What is the problem?

For most of the people in these countries who can scratch together an income of perhaps a dollar, or maybe more, a day, hearing aids when they are needed are totally, unaffordably expensive and even when we can provide them with a second hand donated hearing aid they cannot afford the batteries needed to keep them working. A solar powered charger for hearing aid batteries may be the answer for these but that is another development project.

What is the suggested solution?

The old fashioned body worn hearing aids are nowadays no longer seen but now that almost everyone seems to be wearing – wherever they go – a device with cords in both ears, would probably be acceptable – particularly if you were the only child in school allowed to wear one – a status symbol rather than a sign of disability!!

With this in mind and working with an enterprising inventor – Will Williams of Arclight Medical in Liverpool who has produced a solar powered combination otoscope (for looking into ears) and ophthalmoscope (for looking into eyes) – we have come up with the concept of a miniature solar powered hearing aid.

 A solar panel charges the battery incorporated into a PCB for the amplification circuit attached to the back of the panel with an input pickup microphone and output to earphones to both ears. A miniature USB port with charging circuit could usefully also be incorporated into the design for use when a power boost is needed. Whether or not an on/off switch is required will have to be considered. The circuitry would have to be waterproof sealed.

What about the amplification needed?

In these countries the two commonest causes for hearing loss are middle ear disease and various causes – including ageing – for inner ear hearing loss.

Middle ear disease tends to cause what we call a conductive deafness because of damage to the sound conduction pathway through the middle ear and this is typically a “flat” hearing loss of between 30-50 decibels as depicted on an audiogram. In other words the loss is much the same over all the tested frequencies between 125 – 8,000Hz. To boost their hearing they would need simple amplification of the same magnitude across these frequencies – probably suitable for an analogue design with a gain of about 30 decibels.

Ageing – and other causes for what we call sensori-neural deafness because the damage is to the inner ear (sense organ) or neural pathway into the auditory centre in the brain – tends to produce what we call a “sloping” hearing loss with the hearing better in the low frequencies but falling off in the higher frequencies. To boost their hearing they would need amplification that increases from low to high frequencies – needing a digital design with a gain of about 30 decibels in the lower frequencies rising to about 50 decibels in the higher frequencies.

In other words what is needed are two pre-programmed models – one for “flat” amplification and one for “sloping” amplification. Of these the priority is probably for the “flat” amplification because this is what most of the children with hearing problems require.

However, although we have got to the stage of producing a 3D printed mock-up of the concept, neither of us has the knowledge or the skills to take the design, production of prototypes and testing any further and this is what is now needed.

Are you able and if so would you be willing to help?

If so then please contact me, Chris Prescott

My e-mail address is;


I will be in the UK until 5th March and while here my phone number is




 Leave a Reply