Technology » Hearing Aid (FABLAB)

 Hearing Aid
A very special note about human-ear is that humans do not posses control over activity of this vital organ. An incidental sound has to be heard by a human being unless she /he is sleeping or unconscious. Ofcourse there are artificial ways, but natural. However, another fact is that everyone of us may have different capacities of listening to the same sound. We range from people who can listen to even a slightest noise to people – completely deaf. This particular document intends to connect a technological solution (to this problem) and the socio-economical (and why not political) conditions in India (and countries alike). We encourage the readers to implement the device and/or provide us with their inputs and/or observations.

Current Status: Device is under testing. We are able to reduce the cost to substantial level. This will be available as D-I-Y kit for students.

Concerned Person: Amitraj Deshmukh & Pawan Bhaise

Contact Details: Vigyan Ashram Pabal, Dist. Pune - 412403 Maharashtra, India Phone No. : 91 2138 292326


Tags: Hearing aid, ,


  • This is an Low cost – qualitative Hearing Aid
  • This device is Light in weight and easy to repair/ maintain


  • Possibility of Wireless headphone
  • Increased sensitivity (which is a function of microphone as well as the gainof the amplifier)
  • Rechargeable power supply (preferably over solar power as most of theIndian parts have to undergo load shading at some point in time)
  • Better headphones that can fit into the outer-ear
  • Better packaging (not only easy to handle but rugged enough to withstandweather conditions).

How to do?

  1. A fact (which we can validate is) that a microphone generates very weak signals –in the range of 20 mV or so. On the other hand a headphone requires somethinglike 2V to sing.Based on the information above, we now decide to design an amplifier withatleast a gain of 100. Fig. 7 depicts some electronic components, which can betalked about as follows - R6 – This resistor works as a current limiter for microphone. It avoids themicrophone to be exposed to high current being released from the battery.
  2. C1 and R2, together form a filter that allows only AC signals to passthrough and the DC signals (if at all present) are barred from going ahead.In the absence of this filter one might have to listen to a constant hum inaddition to the signal of interest.
  3. R3 and R4 are the main players to decide the gain of the amplifier. Theyhave been selected in such a way that the amplifier has a gain of 100. Thatmeans changing these would also change the gain. R3 and R4 are related toeach other
  4. Gain = 1 + (R4/R3) = 1 + (100KOhm/1KOhm) = 101 R5 – This one is a variable resistor that allows the user to choose a rightintensity of output volume. In short this works as the volume control

Related Images

Related Documents

PDF Icon Manual to Make Hearing Aid English
PDF Icon Manual to Make Hearing Aid HINDI

Related Links