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Hmmm.
Looking at: https://journals.plos.org/plosone/article/figure?id=10.1371/...
I'm not sure I believe the graphs.
For example, here's another frequency response chart of some stethoscopes: https://www.researchgate.net/figure/a-Frequency-response-of-...
How is it that professional stethoscopes can be that different, and yet this 3D printed one can match a gold-standard one almost exactly?
From what I can tell there's no audio engineering / modelling that's been done here -- It's just some crude openSCAD tubes. And it's not even optimized for 3D printing; a 3D printed tube with a circular cross-section is going to have bridging issues at the top which will result in internal roughness. I have to imagine that results in attenuation. (A better internal shape for a tube is something that looks like "ô". The ^ will print much better)
The type of plastic used and its frequency response, the thickness / stiffness of the silicone tubing, the height / width of the bell... There are so many variables that I think would make significant differences in performance. The fact that they see basically no difference is highly suspect.
This feels like one of those "3D-print everything" fads that was popular a few years ago. Yes, you can make a 3D-printed adjustable wrench, but even the most miserable dollar-tree metal version will beat it in every possible metric.
Likewise, on Alibaba, if you order 200 pieces, I'm seeing metal ones as low as $1.22/pc. I don't believe that this 3D printed one will even be as good as those.
It's a bit of a head scratcher.
It would require abject incompetence on the part of jellybean stephoscope manufactorers for this to make sense.
On the other hand the reason Litmann stephoscopes are expensive is target market (doctors), build quality and amortization of cost over probably a decade of use. Stephoscopes are a metanym for doctor, and doctors don't want cheap stephoscopes.
It reminds me of the product to make budget incubators for developing markets. I can't find a link but it failed for two reasons, if you can't afford medical grade systems. You probably don't have the highly trained teams needed anyways.
Medicine is in large part a trust based endeavour you need to trust the system you are putting your life at the hands of.
Long story short, this solves an imagined problem. When you consider why X doesn't have Y medical system. It's not because of the price of the kit. It's the entire system that is too expensive. If you can't afford a brand incubator you probably can't afford the it intense cleaning regime needed for the room to put that incubator in!
You can measure all the parameters you want. The question is: does it really matter? I know many doctors, and one of my favorite questions is about stethoscopes: I have unanimously the answer "I could just roll a piece of paper and if the room is quiet enough, I can do my work". My grandpa used one made out of wood, just a cone.
Once, I was fascinated by a Littmann, with bluetooth audio, I told a friend doctor, that would be great (thinking about a present) the answer was "That is all hype, I can do with a $2 piece exactly the same". I pointed out the possibility to record the sound, to possibly defense in case of being sued: she laughed out loud, said is unpractical to record everything, would take too much time, and again, just a toy.
That label the graph "log dB" which seems a very odd choice if you wanted to show differences
Amazon in India will sell you a pretty reasonable stethoscope for for $3.
Assuming the usual Amazon, distributor and retailer markups, these probably cost around 50 cents to make in China.
https://www.amazon.in/BPL-Medical-Technologies-ST-01-Stethos...
Many poor countries are perfectly capable of manufacturing their own medical equipment
Background: I have worked in hospitals in Bihar & Vellore Tamilnadu, and have university mates, friends and family who worked in hospitals in Mizoram, PNG, Libya, Nepal, Uganda and even South Sudan.
Even the doctors who worked in South Sudan had no difficulty sourcing basic equipment. They did however, have enormous trouble sourcing funding and trained personnel who were willing to work in a potentially lethal situation.
This has been used in Gaza to make their own due to Israel’s blockade.
https://logicmag.io/bodies/tarek-loubani-on-3d-printing-in-g...
The thing is that I can get just as good if not better ones (metal) for $7 all day long, and not have to spend time sourcing and assembling materials, and I don't even have to leave my house to do it.
When my kids were little they had a toy doctors set and the fake wooden stethoscope broke; replacing it with a real one was significantly cheaper than paying Melissa and Doug for a new one.
I'm not sure what you are buying, but it wouldn't surprise me if they were done in a factory that does medical grade quality control. While the odds are a medical problem from a non-medical grade stethoscope seem low, it still seems a couple bucks is worth the price. (if we are talking thousands I'd ask for a deeper drive into what that really gets you)
Respectfully, as this is HN, I do not believe that is the purpose of the posted Github repository.
From my experience in manufacturing engineering, if they retail for $7, the cost of goods sold is somewhere between $2.5 and $5.
The thing is that even if you do that, you still haven't made your own stethoscope, which this post is all about.
Here is an interview with one of the researchers behind this project:
https://logicmag.io/bodies/tarek-loubani-on-3d-printing-in-g...
It explains the project and its motivations. It's been a while since I read it (2019), but at the time I found it really fascinating and inspiring.
Really eye-opening to my western-brain that agreed with higher comments simply comparing the process with ordering a unit off Alibaba and having it delivered. Truth is, there's often a million other parameters that could come up and make a project like this really useful & practical to someone.
https://www.ebay.co.uk/itm/264691582901
(if eBay kills that link, then for future HNers it's a link to an inexpensive bright yellow single-use plastic stethoscope by a company called Valuemed, which have been available basically forever and are for when you cannot risk getting something nasty on your good Littman)
£1.99 in single unit quantities from a dude on eBay.
These things are so cheap in bulk that they'd ship two in every box of Orthogon Gemini microwave links that I used to fit something like 20 years ago before VDSL was a thing to link fast sites to places that'd otherwise be on dialup. They emitted a quiet beeping to help you align them when they were in aiming mode; the cheap plastic stethoscope made it possible to hear that over wind noise, air handling units, and other such clatter.
I still have a box full of them, despite giving a bunch to the nursery my son went a couple of years ago.
What's the point in 3D printing something for $3 when you can buy them in a bulk box for a tenth of that?
Right. There are plenty of cheap plastic stethoscopes on Alibaba. There are even metal ones in the $2 range. If you want to bang out simple parts in quantity, 3D printing is not the way to go.
I was shocked to see that a "brand name" stethoscope is $100+ and even generic ones are $30.
I'm shocked that you're shocked lol.
$100 for a somewhat specialized, durable medical device that has to meet regulatory standards and will be used daily, possibly for years, by healthcare providers to do patient assessments?
A 3D printed option is going to require a 3D printer, appropriate filament and should be unit tested to ensure it's within spec. The durability is going to be suspect no matter what. It's an awesome project and I'm sure would be a welcome addition to the 'boostrap humanity' catalog of 3D printed parts, but for everyday doctors plunking a hundo on a good tool is going to be a no-brainer.
There are cheap, generic scopes (Sprague-Rappaport types) that are very sensitive but the double tube also causes a lot of noise. There are knock-offs of the Littmann scopes in the market. Then there are the scopes doctors usually buy, which are Littmann, Harvey (made by Welch-Allyn) and Heine, and a few smaller makers. No marketer of a high-quality scope wants to sell it at a $30 or less price point, and if you're going to go higher, might as well place it in the same market as the Littmann ($115+). I'll be honest, for emergency medicine use, the Littmann lightweight scope is good enough and cost about $45 when I bought it. But if I actually want to hear the subtleties in a chest, I'll use my personal scope (a Littmann Cardiology IV). Why choose this one? I already know it and they are very consistent. It doesn't feel cold to the patient and it has the right level of sensitivity without much noise. It is a little heavy. If a dog is bucking around, it can go flying and hurt if it hits someone.
Years ago I had my blood pressure taken by a nurse; this was when they did it manually, squeezing the pressure cuff bulb by hand and listening with a stethoscope. The doctor came in later, saw the numbers and frowned, and took my pressure again. She (both were women) ended up with a reading much more within my normal range.
I asked, joking, “So are you just better than her?” “No,” my doctor replied, “She’s better. She gets more practice. I have a better stethoscope.”
They can become a lot more expensive than $100, but the difference between a Littman Cardiology and the $15 EMT student stethoscope is night and day.
> Currently, the stethoscope resulting from this project functions as well as the market gold standard, the Littmann Cardiology III
If this is true, it's a major achievement.
My daughter's toy stethoscope has actual tubing, some sort of diaphragm, and that seems to work reasonably well!
I'm not surprised good results are available for a few dollars.
People buying stethoscopes tend to be reasonably affluent. Some of the pricier ones just look better and people usually buy them when you get into med school (at least this was the case for me), it's somewhat symbolic so why not splurge.
You probably pay for tests and that the company has to be audited for medical diagnostics standards
It is somewhat of a critical tool, so you don't wanna be checked by a doctor who made their own stethoscope or got one for 3 USD on AliExpress.
If it’s your everyday carry used in your profession, just pay for a nice one. It’s really not that much.
If someone showed you how to create a functional $30 monitor, you’d still pay more for a nicer commercial one
Is that a lot or a little?
How shocked are you, in comparison, that a Claude code subscription is $200/month?
$100? So, like 4 aspirin tablets US hospital billing prices?
What's the price per use compared to a standard industrial metal one?
Interesting project.
Feels like the real value here is not beating commercial stethoscopes, but accessibility and local manufacturing. even if performance is slightly worse, being able to produce something “good enough at scale in low-resource environments could still have huge impact.
Curious though has anyone tested consistency across multiple prints? I’d expect variation in material + print quality to affect acoustic performance quite a bit.
I seem to remember a major issue re 3d-printing medical things. Early in the pandemic LTT organied an effort to print some PPE face shields for hospitals. It was all rejected. The microscopic holes left in the print material meant it could not be properly sanitized.
A stethoscope touches both patients and providers. This may be a place where smooth non-printed material may be the only sanitary choice.
No pictures? Missed opportunity. Seems cool though!
The linked paper has some pictures: https://doi.org/10.1371/journal.pone.0193087
I can buy cheap ones online from Temu for $3.
However I am comfortable with my Littmann.
Littmann's last for 20 plus years.
Do the design and materials take into account how well it can be sterilized?
Never seen a UK doctor or nurse attempt to clean, much les sterilize, one.
I regularly wipe my stethoscope, but I have never sterilized it. I doubt many would survive an autoclave.
Are sthethoscopes passive or active devices?
It's basically a tube that transmits sound waves from a diaphragm to your ears. Pretty much an extension of your own ears.
Nowadays they do make electronic models. Active enough, I suppose. Can even record sounds.
passive
What we need now is open-source ultrasound devices.
As an early-adopter of POCUS, I can't quite believe we actually still use stethoscopes
Instructional video: https://youtu.be/u-KNTc0POLA
Part of it is this - you get hired by Anthropic making $250k a year. They give you the latest MacBook Pro, a nice office, and a $5 Walmart mouse.
It works. Probably fine.
But it’s weird.