LoCHAid – An ultra-low-cost, affordable and accessible hearing aid device
biorxiv.org
biorxiv.org
Zero innovation, and an implementation that wastes lots of power. Why would you use a volume potentiometer at the OUTPUT of the amplifier? It turns most of the output power into heat. And why would you use a stereo amplifier and short the two channels together to get a mono amplifier?
You can already buy (in ear) hearing aids for less than $3 from China. A little bit more money even gets you rechargeable ones.
Also: Even in developing countries, more and more people have smartphones. In fact it might be easier to get a smartphone there than a professional hearing aid. There are apps that act as a hearing aid, taking the sound from the microphone, amplifying and filtering it, and sending it to the headphone output. Unlike with this project, the use can individually adjust the frequency response to his hearing.
The github repository containing the STL files: https://github.com/bhamlalab/LoCHAid
I remember seeing my grandmother's aids. They had a little knob on the side to adjust the volume, and if she turned one to high they would produce an ear piercing loud 'shriek' for eveyone in the room.
This was years ago, I'm sure the technology has progressed since then. But now that I really think about it, how does a device like that just not accelerate hearing loss.
We know we're not supposed to listen to earbuds/ headphones too loud, or risk ear damage. Seems like hearing aids are a kind of earbud that amplify external sound.
Seems like a high risk of folks blasting the volume, and damaging already poor hearing even further. Or a least a sure path to a nice case of tinitus over time.
What am I missing?
Most hearing aids don't deliver sound directly to the damaged ear canal, but also utilise other sound delivery mechanisms. Like induction. This can help prevent damaging the ear internals further.
They also rarely deliver a 1:1 version of the sound in the world around us, because a damaged ear drum already distorts the sound it receives. There is no need to make it harder for the brain to filter out background noise. These filters can be simple - a dial switch on the device, or they can be complex - adaptive filtering based on the current environment. The filter complexity and effectiveness is usually reflected in the price, but as software gets better and hardware more powerful things are slowly shifting towards a better median.
The higher-end hearing aids can also be tweaked by the specialists involved to avoid frequencies that can further damage the ear, but that tends to be on a case-by-case basis and is difficult to tune correctly for an individual.
But you're right - if the hearing aid isn't tuned correctly, or the individual regularly just turns it all the way up, it can lead to further loss. Which is why many doctors have regular appointments to check the device is in a safe range.
The bad habit of the user, turning the device up, can usually be prevented by better sound filtration. They're turning it up because they can't hear something they're trying to focus on, making it easier to focus at lower volumes can curb the habit.
I don't think this is correct. All hearing aids do work this way, and I also don't know of any way that (electromagnetic?) induction could be used to deliver sound.
In a person with hearing loss, not all frequencies are affected equally. Hearing aids can compensate by
1. Amplifying the affected frequencies (this is by far the most common approach) or
2. Compressing and pitch shifting the sound to a range that the user has better hearing.
Maybe they meant [bone] conduction?
The GP was referring to induction output - of which comprises a minority of hearing devices.
- We don't really care if we further damage the hair cells that don't work.
- Outer hair cells amplify sounds. If they don't work, well, gotta amplify them some other way.
- A phenomenon called "recruitment" can cause loud sounds to be more painful for those with hearing loss. So you may not be able to amplify everything.
Hearing aids are a bit more sophisticated than an amplifier; they also act as an equalizer, compressor, feedback cancellation, and a bunch of other features of dubious benefit.
Only in cases of sever to profound will a hearing device be programmed to exceed a safe normal hearing level.
Outer (inner actually) hair cells receive an input and there movement sends an electrical signal down the auditory nerve. In cases of hearing damage these hair cells are not as receptive and require a stronger "push" to move.
Dubious (in your opinion) or not, the other features are designed to improve the understanding of speech especially in noisy situations.
=============== Hearing aids cost a lot of money. no question. But they are not just devices pulled from the shelf and stuck in your ear. They require both initial settings (derived from hearing exams) and frequent follow ups as the user adjusts.
FYI - The ear piercing shriek you heard was from poor feedback cancellation on the hearing aid. Hearing aids have a microphone and speaker so feedback is common and a nightmare.
Also, I'm the founder of AudioFocus (YC S19)
[1] http://www.hearingresearch.org/ross/hearing_loss/the_audiogr... [2] http://openaudio.blogspot.com/2017/01/the-need-for-dynamic-r...
The diagnostic process for getting them involves playing a set of random quiet tones, and you press a button whenever you hear one (and not when you don't). This produces a hearing profile showing how much hearing loss you are experiencing and at which frequencies. Usually the higher ones. If the profile is bad enough and you are given the hearing aids, the profile is downloaded into them and used as a parametric equaliser.
The amplification is not user-controllable, so you can't set it to dangerous levels.
There is also feedback cancellation - there may be a small shriek on power-on (along with the cheerful bootup chime), but it detects this and mutes that frequency.
They aren't magic, but they do make it much easier to understand speech, especially consonants and 's' sounds with high frequency components. Also little things like being able to hear my oven timer's high pitched beep when not in the kitchen.
There is a latency on the amplification and filtering. The ear adapts but I can occasionally notice it.
Battery life is about a week from non-rechargeable zinc-air batteries, £10 for 60 from Amazon or free on the NHS if you can be bothered to go to them.
Often subsidized hearing providers will be given low-cost older hearing aids from manufactures.
Something like a smartphone handling the initial processing and then transmitting via a small earpiece inside the ear with some innovative design for making it discreet.
Hearing aids really are a racket for most part.
> The LoCHAid costs only 98 cents (<$1) to mass manufacture and can be personalized for each user through a 3D-printable case.
> It is designed to be an over-the-counter (OTC) self-serviceable solution for elderly individuals with ARHL.
> Electroacoustic measurements show that the device meets most of the targets set out by the WHO Preferred Product Profile and Consumer Technology Association for Hearing Aids.
> Simulated gain measurements show that the LoCHAid is well fitted to a range of ARHL profiles for males and females between the ages of 60-79 years.
> Overall, the measurements show that the device has the potential to benefit individuals with ARHL. Thus, our proposed design addresses a long-standing and grand challenge of affordable and accessible hearing technology for every elderly person on this planet.
Not everyone can design a multi-stage audio filter, design a PCB or have access to a proper measurement lab.
They say they are personalized, but that seems to only be for physical fit.
I suspect, but do not know for certain, that they also need to be tuned to the individual sonically. This would be make things understandable instead of shrill, and prevent additional hearing loss from overamplification.
Maybe the same as getting eyeglasses that don't match your prescription.
The challenge will be how to fit a hearing aid without an audiologists help. This will be especially difficult for older people.
Hopefully it will bring down the price of hearing aids substantially though.
[1] https://www.warren.senate.gov/newsroom/press-releases/bipart...
Noise cancellation headphones could be easily transformed into hearing aids with a change of the firmware. In fact, they could be excellent hearing aids, because they probably have more computing power than the average professional hearing aid.
Sorry if these were answered in the PDF. A quick CTRL+F on the preview did not find any of these keywords, and I'm too lazy to SciHub right now.
Analog solution.
> How many input channels?
The microphone amplifier is single channel, the output amplifier is stereo, though they only use one and drive both jack outputs from the right channel.