Open source hearing aid - how it works

Engineers at Purdue University and colleagues introduced Tympan, an open-source hearing aid. We tell what it consists of and what people think about it.

Photo kyle smith / Unsplash

Why did Tympan appear

According to WHO, more than 5% of the world's population — 466 million people — suffers from disabling hearing loss. It implies that the difference in the volume of sounds that the left and right ear perceives is 40 dB in adults and 30 dB in children. For comparison: the volume level of 30 dB corresponds to the tick of the clock.

In the United States, $ 750 billion is spent annually on resolving hearing loss problems. However, this amount does not include expenses for hearing aids - in most cases they are not covered by medical insurance . Given that the cost of such devices can reach four thousand dollars, for many they become an inadmissible luxury.

Engineers from Purdue University and a number of medical laboratories decided to propose an alternative. They developed the Tympan hearing aid, which costs only $ 300. At the same time, the project is completely open - the program code for the firmware is available on GitHub , there is also a description of the hardware - so you can not buy the device from developers, but assemble it yourself.

Among the authors of the project is Joel Murphy (Joel Murphy), who participated in the creation of an open source heart rate monitor Pulse Sensor and an open neurocomputer interface OpenBCI . Another iconic figure is Eddie Wagenknecht, who has been the chair of the MIT Open Hardware Summit conference for a long time.

How it works

Hardware part. Teensy 3.6 is selected as the baseboard. It has a built-in USB port and supports SD cards. You can program it using the Arduino IDE. To work with sound, the TI TLV320AIC3206 chip is used. It performs the functions of a DAC and ADC, as well as an amplifier. The board has built-in microphones, connectors for external microphones and headphones, a Bluetooth interface and a battery.

Software. The code is “packaged” into the Arduino library. To work with sound, it presents filters with a finite and infinite impulse response, signal level detectors, as well as fast and inverse Fourier transform functions.

Most Tympan device components (such as microphones) can be changed by users at their discretion. However, audio codecs and the processor cannot be replaced.

On GitHub, developers also provide the acoustic parameters of the device. For example, the maximum value of the output signal is 121 dB, and the noise level at the system input is 39 dBA .

What do people think

The Tympan device has already been acquired by an engineer from New York. According to him, the first tests were successful - most of the questions were covered in the documentation provided, and the developers themselves promptly commented. In the future, the user plans to give the hearing aid to his hearing impaired mother. Residents of Hacker News also noted the benefits of the project. They believe that in the future, Tympan is able to solve hearing problems in many people.

Photo by JD Mason / Unsplash

Although most of the reviews were positive, there were those who expressed a number of doubts. For example, there is an opinion that the operating parameters of an “open” hearing aid will be worse than with more expensive proprietary gadgets. Resident HN said that the development of such devices requires deep knowledge in signal processing and noise reduction. Conducting serious R&D in these areas requires a significant amount of resources, which open source project developers may not have.

It is also likely that at some point the project will begin to experience difficulties with licensing, since healthcare is one of the most stringent and regulated areas where it is customary to rely on the protection of their developments with patents.

Commentators also noted that Tympan uses a fast Fourier transform. This is a resource-intensive algorithm that can adversely affect the battery life of the hearing aid. In addition to this - all the risks associated with potential harm to health that theoretically can cause any gadget, in this case, the user of the system assumes. And it cannot claim any compensation, since it uses an open project at its own risk.

Other projects

Large companies are also involved in developments in this area. For example, a year ago, Google, together with GN Hearing, which designs audio technologies for hearing impaired people, began designing a protocol that would allow connecting hearing aids directly to Android smartphones. It was named ASHA (Audio Streaming for Hearing Aids), and it uses Bluetooth 5.0 Bluetooth Low Energy technology to extend the life of the devices.

In addition to hearing aids, other honey also appear in open source. gadgets. For example, the same Joel Murphy is involved in the development of the OpenHAK fitness bracelet. Its goal is to give device users more control over their data. Also, developers want to expand the pool of functions that fitness bracelets perform. The first applications for OpenHAK are already available on GitHub .

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