Binoreille (english doc)

 
Tutoriel
Hearing aid for deaf from one hear.
  • Difficulty : Abordable
  • Duration : 4h
  • Budget : 120 euros
 

Introduction

The Binoreille project targets deaf people from one ear. The device allows the sound to be received from the side of the deaf ear and is transferred to the functional ear. In this prototype, the equipment consists of a headset and a box containing electronics for sound processing.

The first version was built during the "Abilympics 2016" in Bordeaux. Simon Juif had proposed a solution using a teensy electronic card which is powerfull and small enough for future miniaturization. The limit we had then encountered concerned the listening device, a basic headphone fitted on the top of the ear for not preventing the functional ear to hear its environment on its side.

The second version was built during the Fabrikarium in Toulouse in october 2016.

Team from Fabrikarium :
Prototypeurs : Valérie Guichon, Guillaume Pirou, Pierre Merssadier, Adrien Schmouker, Patrice Caule, Jérôme Terrier, Jean-René Coulon, delphine Bézier
Documentation Flossmanuals : Pierre Commenge

By understanding the designs, plans, components or assemblies related to My Human Kit prototypes, I understand and agree that any information or material indicated by anyone associated with a design team is released as is without any warranty of any kind and is intended to be shared for the purpose of replicating, modifying or improving the plan. I understand that these prototypes aim to develop alternative open source solutions for people with disabilities. I understand and agree that any person associated with My Human Kit could not be responsible for any injury or damage resulting from the manufacture or use of these prototypes.

 
 

Operating principle and choice of headphone

In order to not disturb the hearing of the hearing ear, the chosen headphone is a bone-conduction one which is placed on the temple rather than in the hollow of the ear. A small microphone fixed on the headphone, on the side of impaired hearing leads the received sound towards the hearing ear, after treatment.

 
 

Bone conduction

Bone conduction is an alternative form of hearing. The sound emitted through the transducer of the headphone is transmitted through the skull until intern organs of hearing, without going through the ear drum.

Operating principle

The outside sound is picked up on the side of the damaged ear through an electret microphone. This microphone transforms the accoustic signal into electric signal, which is filtered in a first circuit in order to limit interference signals and adapt the voltage level. Then, the signal goes in the mic input of the audio card to receive a digital processing.

Three successive filters are applied on the signal: a high pass filter at 300 Hz, a low pass filter  at 12000 Hz and a variable band pass filter defined by two poteentiometers: frequency (for the central frequency), width (to define the width of the frequency range). The third potentiometer adjusts the volume towards the headphone.

This prototype is based on a Teensy 3.2 microcontroller card.

 

 

Prerequisites

  • Arduino environnement should be installed.
  • Know how to use a 3D printer
  • Know how to use a lasercut machine
  • Know how to weld
 

Prototype

During the making of the prototype at the Fabrikarium in October 2016, the following versions of software were used:

  • audio adapter “audio shield rev.b”
  • Teensy v3.2 microcontroller
  • Arduino IDE version 1.6.12
  • Teensyduino version 1.30
  • Teensyloader version 1.15
  • 3D printer Bicephale Mark One
  • Laser cutter Trotec
 

Download

Download <a href=”https://github.com/myhumankit/Binoreille”>the following folder on github.</a>

 

 

Welding the components

Prepare the components in the following order:
- Weld the two female pin headers (14 pins) on the audio adapter.
- Weld the female pin headers (2 pins) on the mic input of audio adapter.
- Weld the two male pin headers (14 pins each) on the teensy card.
- Weld the female pin header (4 pins) on the regulated output power for the potentiometers.

 

Preparing the 3 potentiometers

1- Cut 3 wires of about 7 cm length.
2- Use a wire cutter to remove sleeving and free the wires on 1 cm length.
3- Tin bare ends to eliminate fraying.
4- Solder the wires on the 3 potentiometers as shown on the picture below

 
 

Preparing the electret microphone

Use a cutter to remove sleeving and free the wires from the mono shielded cable. Use a stripping pliers to remove sleeving of the little wire inside. Tin each side of the little wire and tin also the copper wire on each side after having rolled it on itself. Solder the copper wire on the (-) of electret microphone and the little wire on the (+) of the electret microphone.
The microphone is ready to use.

 

Filter circuit

In order to reduce stray sounds due to the microphone cable length, it is recommended to add a filter.
Get some stripboards (veroboard, 8x8 holes)
Solder the filter circuit as shown below (the cable is long and has an antenna effect. This filter reduces stray sounds and reduces the voltage with a voltage divider before going to the audio adapter).

 
 

Filter connexions

Connect the filter to the Teensy card by refering to the schematic below.

Connect also the microphone (+) on the mic input of the audio adapter and the ground of the mic (-) on the ground input next to the mic input (+) of the audio adapter.

Add a button ON/OFF with the SPST (switch) between the ground of battery (-) and the ground of the Teensy as shown on the schematic.

 
 

Assembly diagram : Teensy+ Audio adapter + other components

Stack the Teensy card on the audio adapter as indicated on the following diagram.
The ON/OFF switch is not drawn on this diagram as it was added after the drawing.
Then plug the potentiometers and the battery as shown above.

 
 

Installation of Teensyduino and Arduino configuration in order to load the program on the Teensy card

  1. Install Teensyduino (plugin for arduino IDE ) https://www.pjrc.com/teensy/td_download.html
  2. Plug the Teensy to a USB slot of the computer
  3. Open Arduino software
  4. Open the code from the downloaded folder.
  5. In Arduino IDE, choose Teensy 3 card in the menu Tools/board
  6. In Arduino IDE, choose the right port in the menu Tools/port
  7. In Arduino IDE, click on rhe icon “check” (lthe first one on the left!)
  8. In Arduino IDE, click on upload
 

Making of the box with lasercut machine

The box made here is far too big to be easily transportable but it is functional for a prototype still under development.

The original SVG was created thanks to parametric generator box from "la Cité des Sciences".

The holes were added with InkscapeSVG à la découpeuse laser.

Glue all elements together except the covert to constitute a solid box.

 
 

Assembly

Fix the potentiometers.

 

Safety precautions

Congrats! The build is done and you can test the prototype. In order to prevent your audition from any trouble, it’s necessary to pull down the volume at the maximum before you plug the prototype on the battery. You can then adjust the volume slowly at your convenience.

You can use this prototype by fixing the microphone on your sleeve for example, or holding it in your hand keeping it at a safe distance of minimum 20 cm from the headphone. Please carry out theses security tips, else you could damage your hearing!

Issue to solve before fixing the support on the headphone: We tested an integration of the microphone on the headphone but this prototype is still under development, and we have not yet resolved the larsen issue triggered in this configuration.

We would be pleased to collect  your feedback and your observations as well as your possible improvements that we could include in this tutorial. So, please don’t hesitate to contact us 🙂

 

 

3D printing of the microphone support in order to fix it on the headphone

You will find on the thingiverse from My Human Kit the 3D model of the microphone support designed to be fixed on the headphone we used.

This 3D model is a support designed for electret microphone MCE-100 which is supposed to be fixed on the headphone Aftershokz Sports M3, when the larsen issue will be fixed.

This modelisation was created by Jérôme Terrier during the Fabrikarium in october 2016 specially for the Binoreille prototype.

The intégration of the microphone on the headphone represents actually a danger for the hearing for the reasons mentionned aboved. It is supposed to be tested with caution and only if you have a solution to prevent the larsen.