Need a microphone to record heartbeat

Ya’akov

Joined Jan 27, 2019
5,642
currently i am trying to use microphone of my headset to record but its not efficient so any other approach is fine
thanks
Welcome to AAC.

It would be an enormous help if you would explain why you are trying to record a heartbeat. Context will help provide good advice. As it stands there would just be a lot of guessing and by some chance we might be helpful.

Your part in the process is to explain the problem you are trying to solve, not the part of the solution that is eluding you. First explain why then explain how you are trying to do it and the trouble. The results will be much more satisfactory for everyone.
 

Thread Starter

headydeadpool

Joined Apr 19, 2022
14
I am working on a low cost heart auscalation device , as because of covid doctors cant really wear stethoscopes all the time so she asked me to make a device which will provide the heartsound recordings on speaker or her laptop. so i tried using bluetooth headset and parrot app but it didnt quite worked properly so i would like your suggestions on how should i go on about this ? will microphone with arduino would be a wise choice ?
any suggestion works. Also it would be really helpful if you can also let me know where can i get the suggested device or microphone because i am not an electonics major and have zero knowledge in this field.
Thanks
 

Ya’akov

Joined Jan 27, 2019
5,642
https://journals.physiology.org/doi/full/10.1152/advan.00073.2012 is how I would have expected it to be done. The article seems to provide enough information to do what you want in terms of the microphone.

It could certainly be made wireless using Bluetooth. Part of what I don’t know is how this would be used. Is this in an ordinary clinical setting or something else? Does the heartbeat need to be recorded or just monitored?

Also, what is the budget for this?
 

Thread Starter

headydeadpool

Joined Apr 19, 2022
14
yes it is in ordinary clinical setting and only monitoring is fine also.
budget is basically as cheap as possible but it can go upto 100$
 

LowQCab

Joined Nov 6, 2012
2,036
This idea is not very practical.
Heart-Beat-Sounds are very Low-Frequency.
This works just fine with a Stethoscope directly to your Ears,
but reproducing this in "open-Air" requires Speakers with very good extreme-Low-Frequency-Response,
this translates into VERY large and powerful Speakers.
High-Quality Headphones "might" provide satisfactory results,
but there is a wide variety of variations in the Low-Frequency-Response of both Speakers and Headphones.

There is no reason to amplify any Frequency over approximately ~200-Hertz,
everything higher than that should be electronically filtered-out, as it is just extra "noise".
Frequencies as low as ~20-Hertz could be important to reproduce accurately,
and a Stethoscope can easily do that, but not very many "desktop" Speakers can.
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Audioguru again

Joined Oct 21, 2019
4,658
My Electronic Stethoscope uses a cheap electret microphone mounted in a hole of a plastic lid from a jar. It is amplified with an opamp circuit that has a good response at low frequencies. A switch with high frequency filter is used for cutting higher frequency noises or for receiving breathing sounds. A speaker and power amplifier can be used only to play back a recording to avoid acoustical feedback howling.
 

MisterBill2

Joined Jan 23, 2018
11,874
AG is correct! and experimentor electronic stethoscopes have been published back when they used tubes for the amplification. An electret microphone is OK, but a crystal microphone was claimed to produce the better results,probably because of a much larger diaphram area. So certainly it can be done using almost any generation of technology, although batteries and tubes is not a good choice. Probably the headset microphone is the least satisfactory choice.
One interesting possibility would be to use an actual stethoscope and connect the ear tube to an electret microphone, since those are available with quite small diameters. You still need a bit of gain, although running the electret directly to the computer microphoneinput should produce some results.
 

Ya’akov

Joined Jan 27, 2019
5,642
AG is correct! and experimentor electronic stethoscopes have been published back when they used tubes for the amplification. An electret microphone is OK, but a crystal microphone was claimed to produce the better results,probably because of a much larger diaphram area. So certainly it can be done using almost any generation of technology, although batteries and tubes is not a good choice. Probably the headset microphone is the least satisfactory choice.
One interesting possibility would be to use an actual stethoscope and connect the ear tube to an electret microphone, since those are available with quite small diameters. You still need a bit of gain, although running the electret directly to the computer microphoneinput should produce some results.
You missed this:

https://journals.physiology.org/doi/full/10.1152/advan.00073.2012 is how I would have expected it to be done. The article seems to provide enough information to do what you want in terms of the microphone.
 

MisterBill2

Joined Jan 23, 2018
11,874
You missed this:
I certainly DID miss it. My contribution is that the cartridges are also available from places like Digikey. But if an old computer headset is available for salvage then the really hard part will be the soldering the lead to the cartridge. Many folks are unable to do that at all.
 

LowQCab

Joined Nov 6, 2012
2,036
Electret-Microphones are not all the same.
Many Headset "Boom" Microphones are specifically designed with a limited Frequency-Response and
may also be of a "Noise-Cancelling" design,
either of which would render them useless at the required Low-Frequencies of a Stethoscope.

Brand-new Electret-Mics are dirt-cheap,
and usually come with documentation demonstrating
an amazingly Flat-Frequency-Response to below ~15-Hertz.

Here's an excellent example .........
https://www.digikey.com/en/products/detail/pui-audio-inc/POM-2738L-LW100-R/5414025?s=N4IgjCBcoGwMwAYqgMZQGYEMA2BnApgDQgD2UA2iHABxjUAsSxEAusQA4AuUIAypwCcAlgDsA5iAC+zAJzUZyEGkhY8RUhRBI2ILj37DxU4gCYw9AKyLlqgsTKRKYCwAIAEgC8XAPxdgYLgDWniA6epAgAEqY4vgAqiJCnADy6ACy+Ji4AK4C+MYgALRW0EoYOHYajiAwJiDEMBDEcPUgdcwA7KHSRTDWUILZ6g6ULSw9hXWlyoPDmgrjPVOU+Nj4KIL4nC4AtkIoAiTsABYkIvnjQA
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MisterBill2

Joined Jan 23, 2018
11,874
YES, Idid mention Digikey in post#12 , and they have 1600 0f them in stock. And all kinds of data and useful information about the parts. So couple that , and note the extended connection so no soldering on the element itself., to a cable to the computer Mic input and there is your system.
 

Thread Starter

headydeadpool

Joined Apr 19, 2022
14
My Electronic Stethoscope uses a cheap electret microphone mounted in a hole of a plastic lid from a jar. It is amplified with an opamp circuit that has a good response at low frequencies. A switch with high frequency filter is used for cutting higher frequency noises or for receiving breathing sounds. A speaker and power amplifier can be used only to play back a recording to avoid acoustical feedback howling.
thanks for this though could you let me know what switch you are talking about? it would be great help if you can provide me some links.
 

Thread Starter

headydeadpool

Joined Apr 19, 2022
14
from what i have researched till now i think i will go with electret microphone with op amp as it has frequency response from 20hz to 200hz and heart sounds are in that range but i am not getting any ideas of how to get the output.
need help on that now
thanks in advance
 

MisterBill2

Joined Jan 23, 2018
11,874
i am attaching a microphone i found online could you let me know if this is a wise choice for the project

https://www.electronicscomp.com/max...98pJzD_OL9THVf0xbP6LzJqlm_rn2dQhoCUc0QAvD_BwE
While the performance may be adequate, that listed price of $169 each is totally out of line. Also note that the specifications listed are not to be trusted, as they claim the operating current is 24 amps! If that number is so very far off then I suggest that none of the claims should be trusted.
Given that the "Thinklabs" site does not even mention a price, my guess is that it is quite high also.
So now one question that applies to any electronic stethoscope: Do you have a qualified person who can compare the results they hear with it to the results that they hear with an actual medical grade stethoscope? The proof of any device will be in the performance.
Aside from that, both the "Free Information Society" website and the "Schematics for free" website had electronic stethoscopes in their list of circuits available for downloading. At least they used to have them.
 

Thread Starter

headydeadpool

Joined Apr 19, 2022
14
While the performance may be adequate, that listed price of $169 each is totally out of line. Also note that the specifications listed are not to be trusted, as they claim the operating current is 24 amps! If that number is so very far off then I suggest that none of the claims should be trusted.
Given that the "Thinklabs" site does not even mention a price, my guess is that it is quite high also.
So now one question that applies to any electronic stethoscope: Do you have a qualified person who can compare the results they hear with it to the results that they hear with an actual medical grade stethoscope? The proof of any device will be in the performance.
Aside from that, both the "Free Information Society" website and the "Schematics for free" website had electronic stethoscopes in their list of circuits available for downloading. At least they used to have them.
i think you got the price wrong its 169 indian rupees means 2.2 dollars though i am not quite sure about specs but its cheap so it might be worth a try? , thinklab one is 499 dollars which is why we are trying to make a affordable one.
and yes we are making this for a experienced doctor so thats not a problem.
i will look into the websites you mentioned.
one thing i dont quite understand is how i will get the output, i want it to be recorded on laptop if thats too much then just realtime audio on speaker works too, could you help me out with that?
thanks a lot
( i have little to zero knowledge about electronics as i am mechanical major so detailed explanation and links to site where i can learn is preferable )
 
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