Deaf Teddy- Audio Visual biofeedback training for the deaf

Audio Visual biofeedback training device for the hearing impaired


One of the problems that people with hearing difficulties have is not knowing that they are talking too loud. This effect can be observed in normal hearing people who tend to talk loudly when they are wearing headphones or if there is a lot of noise.

Luckily with a bit of training this can be overcome. One method is to have a system were sound can be electronically converted to light, so when the person talks loudly a light will come on and they can adjust their voice accordingly

This idea has been around for a good while, such methods have included having the person talk with a candle near them, if they disturb the flame they know that they are talking too loud, another would be to have a microphone connected to an amplifier, but instead of it being connected to a speaker, it is connected to a light, the volume control will then serve as your adjustment for the light setting

How it came about:

Mr Theo Blumburg approached me with the concept of having a Teddy Bear that had its eyes replaced with lights that came on when a person is talking too loud. This was to train young people with hearing difficulties, as with most things it is important to train people at an early age

The first unit built was kindly designed and built by Mr George Brenett .This unit however went missing and we had to re-design a totally new unit, which was done this time by Mr Terry McClement & Keith Perks. Please note that copyright exists on this device, however all parties have kindly agreed to make their design free to use and build for training or non profit purposes

While the concept is fairly simple, getting everything to run smoothly takes a fair amount of planning. The unit is capable of working with a wide range of Microphones, from low budget, non-powered mikes to microphones with pre-amps. We decided to use a microphone that did not use any power as this would just be something extra to go wrong (flat batteries etc) Also we bypassed the on / off switch for the Micro-phone for the same reason. It was decided to use Large LEDs (Light Emitting Diodes) instead of Globes as they use very little power, the unit can be used for long periods of time on either a PP3 or PM9 battery – it could also work on a car battery if need be, but is not recommended.

It is fitted with a circuit protector that will cause the unit not to work should the battery be connected incorrectly, future design will see it fitted with an intelligent protector (four diodes) that will automatically work out the correct polarity. The unit contains the following: a control box with an on / off switch and two knobs which control the levels at which the LEDs will work. A lead to connect power. A lead to connect a Microphone

Here is an article in the Daily Dispatch … udley.html

How to use it:

The unit works on 9 volts DC – make sure that the Microphone and power source are connected then switch it on. Leave it to stabilise for a few seconds

Calibrating the unit:

The idea of the unit is that the lights (LEDs) will Visually show the person when they are talking too loud, or too soft. The Green light will show that everything is fine and the voice level is correct, failure to active it will indicate that they are talking too soft. The Red light is set to come on when they are talking too loud and they must try to control their volume

The longer knob is for the Green LED – The Shorter for the RED LED

For first time use start by turning the knobs all the way clockwise (on /off switch to the front)

Talk normally while turning the Green control knob anti-clockwise, you will see that at some point the LED will come on this sets the normal volume level

Talk loudly while turning the Red control knob anti-clockwise, again at some point the LED will light up, this will set the too loud level

The unit then can be used as it is, or mounted into a Toy such as a Teddy Bear – You could even use a piece of cardboard with a face drawn on it

We are hoping to have available soon a circuit board design for download – The estimated cost of parts would be twenty to fifty Rands (appox $3 – 7 USD) The working title of the project is ‘ the deaf Teddy ‘ while not the best of names, it does encapsulate the idea of the project rather well, so it seems to have stuck for now. For my little part in the project I would like to dedicate it to my two doggies, Abbey and Teddy (Bear) who some how seem to fit into the story with their willingness to help and sheer determination

If you would like to know more or contact me:
Paul Wiggins paulw(at) – use the @ sign for (at)

Download the Circuit Diagram Here: … iagram.JPG

The Parts List here:

Video of it working (1 meg)