
Open Source Hardware Hearing Aid Part 1 - zdw
https://shapr.github.io/posts/2019-08-03-tympan.html
======
holy_city
This is a really cool project. The one issue I see is that the Teensy isn't
what you'd call power efficient (compared to some more domain-specific DSPs,
that is).

>That seemed incredibly expensive. I haven’t done much electronics, but
digital signal processing doesn’t seem that expensive?

The cost is in R&D, not just for human trials but for DSP engineer salaries.
It's an extremely specialized skillset and the companies that hire for it look
for PhDs most of the time.

In particular, optimizing adaptive filtering to clock in the dozens of cycles
per buffer with fixed point DSPs to maximize battery life, while providing
features like feedback reduction, noise cancellation, working around the
infamous "cocktail party" problem, with modern features like Bluetooth... all
with audio fidelity on par with some serious audiophile gear.

My understanding is that there are also some other market forces too like very
long lifecycle management and low volumes for new products, but idk how real
that is.

Point is, I don't think those devices are really overpriced - at least no more
than any other medical device paid for by insurance companies.

EDIT:

I'm reading some of their documents and a few things jump out at me. They
mention supporting FFT/IFFTs on the platform. This stands out to me since
doing that on a battery powered device is unusual. Firstly because it's not
cheap in cycles, and secondly because useful FFTs require rather large buffers
of memory which harms your latency, and may come at a premium. When I've seen
them required (e.g, a codec), it was typically on a dedicated FPGA with the
algorithm burned in, not running on the DSP.

~~~
jdietrich
Hearing aid processing chips are incredibly sophisticated and specialised -
just check out the block diagram in this datasheet:

[https://www.onsemi.com/pub/Collateral/SA3291-D.PDF](https://www.onsemi.com/pub/Collateral/SA3291-D.PDF)

That chip is doing graphic equalisation, multi-band dynamic range compression,
noise cancellation, feedback cancellation, data logging and wireless
communication with an absolute maximum power dissipation of 50mW. It's a $100
chip for good reason.

~~~
cushychicken
Every single chip function cited here is available in any given
wearable/hearable chipset, many of which are available in consumer products
that cost less than $100. Economies of scale suggest that the price of the
actual chip that does all that is less than $10. Personal experience suggests
it's likely less than $5 - maybe even less than $2 in large quantities.

A big part of why hearing aids haven't faced much disruption, as I understand
it, is their qualification as a medical device. A major competitor of my
current employer had a policy of many years that they would not do hearing
aids, in spite of extensive audio and audio processing experience internally.
The reason? Amar Bose wanted nothing to do with medical device certifications.

~~~
jdietrich
_> Every single chip function cited here is available in any given
wearable/hearable chipset_

All but one - low power. A typical pair of true wireless headphones runs for
three hours on a charge; a typical hearing aid runs for a week on a zinc-air
cell. Any Turing-complete processor will do whatever kind of DSP you need it
to do, but the trick is doing it incredibly efficiently.

~~~
cushychicken
>All but one - low power

Even that part is becoming less true. I've seen multiple datasheets in the
last year that promise worst case FFT/IFFT performance at 2mA. Measured
performance has been less than a quarter of thst.

------
imglorp
I wanted to applaud the hackability aspect here.

Traditional aids are aimed at (1) old people who can't handle more than 4
buttons on a TV remote, who (2) are willing to accept whatever they're given
and put up with inconveniences, and (3) don't notice their audiologist and aid
vendor are kinda in cahoots to their detriment.

There's all kinds of interesting things aid users might want to experiment
with, once an audiologist gives them a profile of their hearing loss. Aids
have programs that help for different situations, like crowded room, quiet
conversation, etc, and the user may want to adjust those settings themselves.

------
computator
The solution to killing off outrageously-priced hearing aids is to leverage
the smartphone. It has everything that's required to make an superlative
hearing aid: excellent microphone, earphones, powerful CPU, and an all-day
battery. A modern smartphone might not have a DSP but it has sufficient
processing power to do the required audio processing. Many people who'd be
embarrassed with visible hearing aids wouldn't mind walking around with
AirPods or other visible Bluetooth earbuds these days. The hurdle is that the
hearing aid manufacturers will be complaining to regulators that you can't
sell a smartphone as a "medical device".

The Apple AirPods with the "live listen" feature on iPhones (and iPads) is
already being used by some people as a substitute hearing aid. You can use
"live listen" with an actual hearing aid as well, but I've seen people using
it with _just_ AirPods and they seem to find it quite helpful. What's missing
is the software to do the audio processing specific to that person's hearing
loss. Plus overcoming the regulatory burden.

~~~
GregoryPerry
And the likely reason why this is not happening (in the commercial space at
least) is FDA regulatory hurdles in having a product (and probably an entire
company) shut down for making "unapproved" medical claims.

I've got a set of Bose Hearphones, about $500, and which use the Bose Hear
app. You can modify treble and bass but that's about it; even so if you are
hard of hearing then the default iPhone sound profiles can be used to fine
tune the in-ear audio and they work well as a low cost hearing aid. Same deal
with my AirPods. Today Tim Cook could wave a magic wand and literally cure
deafness for hard of hearing iPhone + AirPod users; ain't happening.

No question Bose Hearphones with the Bose Hear app or AirPods with a
complementing iPhone app could easily perform spectral analysis with an easy-
to-use-equalizer, to increase and/or decrease the amplitude of specific areas
of the auditory spectrum; this would be ideal for tinnitus patients and would
without question put the entire hearing aid industry out of business. Current
generation hearing aids are about $15 worth of analog parts that they are
selling for thousands of dollars each, just by virtue of having invested in
some horseshit FDA regulatory process when infinitely more capable technology
has been available to hearing impaired individuals for well over two decades
at this point.

This is not complex, and what sucks about tinnitus is that it affects each
person differently which in turn requires specific auditory tuning for each
individual. But companies such as Bose or Apple that have the technology with
more than sufficient computational horsepower to replace hearing aids simply
refuse to do so, for whatever reasons that are likely FDA regulatory hurdle in
nature.

On a side note as to OP, $300 for a Teensy-based hardware platform with BT
stack is f'ing outrageous, probably worse than what the actual hearing aid
vendors are ripping off.

~~~
andai
> specific auditory tuning

I use a site called MyNoise to play nature sounds to drown out background
noise (neighbors, traffic). The thing that sets MyNoise apart from the other
ones I've tried is that it has a EQ you can tune, and specific instructions
for tuning it: for each frequency range you find the lowest volume where you
can still hear it. The result is a curve matched to your hearing curve -- the
tuning process accounts for hearing loss and tinnitus. Now, if that curve
could be combined with the "live listen" / Bose Hear... then you got yourself
a hearing aid, using hardware you already own!

~~~
jacquesm
It can't give you the one thing that is more valuable than sound: silence. I
wonder what happened to practical applications of 'anti-sound'.

~~~
mwachs
Parent of 2 deaf children here. When our first was born, we were handed a very
thick packet of information warning us that without intervention (i.e.,
hearing aids) our child would be at much higher risk of falling behind in
school and suicide because of social isolation. So, y’know, respectfully, nah.

~~~
jacquesm
Of course silence by choice is a different thing than silence by force. I have
a huge concentration problem and silence is what I crave most when I'm working
or trying to read. That says nothing at all about a child that is born with a
hearing defect.

------
aasasd
Pretty sure that in my country Western imported hearing aids start around 300
or 500 dollars—mostly European ones. And afaik those aren't the ‘just blare at
5x the volume’ type but tuned by the audiologist to the patient's hearing
profile. And they go behind the ear.

2000 bucks are the type with a dozen advanced effects, bluetooth connection to
work as music player headphones, and adjustable with a remote or an app.

So, people in the US might find it cheaper to order European aids or smuggle
something from Canada. (BTW, afaik plane tickets cost way less if you buy them
in the airport just before the flight.)

\----

Also, personally I'd be wary of twiddling the params of a hearing aid since
I'm not an audiologist nor any kind of doctor at all and don't know if my
choice would cause more damage in the long term. And _if_ audiologists mostly
reside at hearing aid dealerships then I'm not sure they will just give you a
chart of your hearing so you can walk home and tune your aid by it.

Ah, and azalemeth's comment reminds me: if the board just has jacks for
headphones then you can't even use the hearing charts without also knowing the
frequency response for the headphones.

~~~
jjeaff
If it were that simple, people would be importing them and selling them
already. Black market or not. But high end hearing aids take multiple in-
person visits with experts for in-depth hearing tests and then impressions for
a perfect fit, then hand adjusting to tune the fit and return visits to tune
the sound and fit.

The technology is probably not the most expensive part of high end hearing
aids. It's the service.

~~~
hadlock
My eye doctor puts me in front of a bunch of lenses and then says "better...
_flip_ or worse?" over and over and we end up with a set of lenses. Without
access to a trained doctor, at first glance (no pun intended) it seems like
you could do a 95%+ job of fitting a hearing aid's sound profile using a
better/worse UI on a phone app and some prerecorded sounds/speech samples. I
have zero experience with hearing loss, though.

~~~
aasasd
Well, you see, sound has this magic quality that the more you jack it up, the
more you hear. Ever been to a concert of a warm homey Ninja Tune artist, such
as Coldcut or Amon Tobin? They turn out to be eye-popping industrial hardcore
on a club's 10000 watt system.

The problem is, it's not good to put too much sound into the ears.

~~~
computator
The person you're replying to didn't say anything about jacking up the sound.
He said, " _you could do a 95%+ job of fitting a hearing aid 's sound profile
using a better/worse UI on a phone app and some prerecorded sounds/speech
samples_". You'd train it--at a constant sound level--by listening to sample
audio recordings and repeatedly saying "better" or "worse". The same way you
need to train a speech-to-text dictation system by repeating a bunch of
phrases, or a fingerprint scanner by repeatedly swiping your finger, or voice
recognition by repeating some words. It sounds like a totally reasonable way
to eliminate high-priced fitting sessions.

~~~
wtallis
Hearing testing for the most part isn't about the patient giving better/worse
feedback. It's about determining the quietest levels at which you can hear
each frequency, and how much loudness you need to accurately identify sounds
and speech. The tester has to assess when the patient's performance is better
or not, because it's blind testing. The patient's feedback is in the form of
either signalling "I heard that", or repeating the words that were just
played.

~~~
computator
> _The patient 's feedback is in the form of either signalling "I heard that",
> or repeating the words that were just played._

Why is a human tester needed? I'm not seeing any reason that couldn't be
automated.

~~~
aasasd
Because a person tuning an aid for themselves is rather likely, IMO, to simply
choose more amplification since they can hear better then. Which will then
backfire when they lose hearing even more. I've seen braggart reports of
people with strong hearing loss and aids able to hear speech from more
distance than healthy people—but is that good in the long term?

Firstly, people already have to be told to not play music too loud with
headphones. And secondly, when you buy an aid, the audiologist tells you that
you won't be comfortable with it for some time until you get used to it—even
though the aid is supposedly tuned to the exact profile of your hearing loss.
People aren't good at getting used to uncomfortable things without adjusting
them to their short-term liking.

On top of that, audio engineers, musicians and graphic artists know that it's
difficult to do fine adjustments of audio or graphics for long because the
senses become tired and ‘burned out’ after a while and you don't see or hear
the same (even just five–ten minutes is enough sometimes). Novices are likely
to be unfamiliar with these effects, have less stamina for them, and unable to
counteract them without overcompensating.

~~~
hadlock
Agreed, that last 5% of fine tuning frequency bands etc you need a
professional, but if you were going to roll out $12 hearing aids to all of the
low income areas of the world 1 billion people at a time, using an android app
on a cell phone you could probably give a lot of people back their hearing.
Volume levels could be hard-limited in software, and people who need to exceed
the preset limits could be referenced to a senior technician in those 5% of
cases or whatever it might be.

Being able to hear even every other word would improve quality of life of many
people. Probably one in three words is the acceptable limit of "good enough"
where suddenly they are worthwhile to hassle with. My grandparents now hate
family gatherings because they might understand only one in five sentences
spoken directly to them because of hearing problems and the quality of the
hearing aids they're able to afford with their insurance.

------
kcbanner
> No way I can get that kind of money, so I gave up on that idea.

I'm curious if the Tympan solution has done this testing? What is the
perceived downside to not doing human testing on what is presumably going to
be a hobby project?

~~~
shae
I asked Tympan about this, they said they've partnered with Boys Town National
Research Hospital and with the National Institute on Deafness and
Communication Disorders.

Those two powerful partners are working on relaxing the laws some so that
small companies/teams could create something like the Tympan.

I'm still not sure if the Tympan is a "human use approved hearing aid" or if
it's just for research purposes. Hopefully I'll have discovered that before I
publish part 2.

~~~
kcbanner
Ah, interesting! Thanks!

