Bone transduction hearing aids

This project proposes a solution to hearing problems, creating a device which uses bone conduction.

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The current hearing devices available in my country, Guatemala, focus on the amplification of sound to stimulate the middle ear, however, in more severe hearing loss a cochlear implant is needed that is performed by surgery and the regular cost is between the two hundred and fifty thousand quetzales in local currency, or approximately thirty-five thousand dollars, it should be emphasized that this is a budget that is not accessible to the vast majority of people in our country.
Due to the aforementioned problems, we propose the design and implementation of a hearing device based on bone conduction, of superficial placement which will not require any surgical intervention, thus also offering a low manufacturing cost, aroun one hundred dollars.

The objective of this project is to create a bone conduction hearing prototype, which suits both children and adults. It is intended to create a low-cost device, which is easily accessible to people. The design in general consists of a microphone which captures the external sounds perceived by the person around it, the captured signal will be taken to a sound amplifier, which at its output will have a bone transducer which converts the electrical signal into vibrations to then be perceived by the auditory nerve.

The prototype aims to be created so that people with hearing problems can regain this sense, being able to return to perform their daily tasks without major problem.

General block diagram

Battery: The battery is the source that feeds the entire system.
Microphone and audio amplifier: The microphone captures the ambient sound that is perceived, this captured signal will be amplified to transmit it to the transducer.
Bone conduction transducer: Converts the electrical pulses from the audio amplifier into vibrations that can be interpreted by the auditory nerve.

  • 1 × Battery
  • 1 × Audio amplifier
  • 1 × Bone transducer
  • 1 × Microphone module ky-038

  • Tests with microphone module

    José Luis04/03/2018 at 02:58 0 comments

    Not having a good performance with the preamp module, I went to a store specializing in electronics, looking for a module that detects the sounds. The only module I found for that purpose was ky-038, which is a module that uses an electret microphone to pick up sounds, ranging from 100 Hz to 10 KHz, covering the detection range of the human voice, incorporates itself into an operational comparator amplifier, the LM393. This module works from a voltage of 3.3V and offers an analogous output for the range of 1Vpp.

    When connecting and testing with the horn, an improvement in the detection of sounds is perceived, having a less saturated sound and without noise.

    When testing with the "bone transducer", it is possible to perceive the sounds, although somewhat weak. The part of this prototype was satisfying, since with simple elements we could perform the corresponding tests, and see that the idea is functional.

    For the following tests it would be necessary to make several improvements, which are:
    • Have a true bone transducer, since the vibrator motor that we used for the tests, was not designed for this purpose.
    • Better the stage of audio amplification, having an audio amplifier that delivers more output watts and a low energy consumption.
    • Design a case with 3d printing, in which all the components are put and be more comfortable to use.

  • First prototype

    José Luis03/27/2018 at 03:10 0 comments

    To perform the first tests and see if it is possible to transduce bone audio, we used a small vibrating motor from an old cell phone, which will serve as a bone transducer. The audio amplifier used is the well-known LM386, which for its operation requires few external devices, which offers a quarter watt of power when voltage is supplied below 5V. Everything is fed with a small 3.7V lithium battery.

    To test the circuit, the audio signal was sent by a cell phone, and using the "bone transducer" it was possible to perceive the sounds, not like you hear on the horn, but you know that bone conduction works.

    A capacitive type electret microphone was used to pick up the sound, but for this to work it is necessary to add a preamplification stage.

    For this test a simple circuit was made using a transistor, ceramic capacitors and a few resistors. The performance of this preamplifier is not so good, when listening with the horn the sound is perceived saturated and with noise, and it is necessary to approach the microphone so that it detects the sound.

    When using the "bone transducer", it is not possible to perceive anything of what the microphone captures. A better preamp circuit is needed, which improves the detection range of the sounds.

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José Luis wrote 05/02/2018 at 21:10 point

Thanks to all the people who took the time to read this post and also to those who liked it, unfortunately I will finance this project from now on, I hope it will change the lives of many people, and my purpose is to reach those who do not have the economic possibilities, we will see in the near future, and I hope this idea is working.

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Stephen Tranovich wrote 03/21/2018 at 23:07 point

This is awesome! I can't wait to see what you do with it!

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