Instructables

Sound wave heart beat detection

I love to graph things. Everything from outside temperature to server room temperature to the number of users on the network to my weight.

I just read an article in Make magazine about DIY ECGs, and it got me thinking.. i want to graph more things about my body :)

Would a microphone embedded in the bed be able to pick up the heart beats and calculate the BPM? This way I could graph development in resting heart rate over time. The microphone would pick up lots of noise from the person moving around etc.. but that doesn't mather. It only needs to get a few clean heart beats in order to calculate the bpm, right?

What hardware and software would be suitable to create something like this?

Any ideas?

Yeah, of course there are other more traditional ways of measuring heart beat.. but I'm to lazy to do that.. I'd rather spend some time making a fully automagickal system.

Kiteman6 years ago
I'm not sure a microphone in the bed would work - it would pick up all your other bodily movements and functions as well. When I have my blood-pressure checked, the nurse or doctor put their stethoscope over the blood vessels in my arm to listen to the flow - maybe strap a small microphone over a convenient point on the body and graph it's output (maybe even just using something like Audacity to record it).
. I've seen some type of optical sensor that is clipped/taped to a finger to get BPM. My friend was wearing one in the hospital when he got his pacemaker. Taped up too well to really tell how it worked, but it looked like a visible light LED on one side, shining thru his finger to a detector on the other side.
They are doppler units. The red light is shone into the finger and reflects off the flowing blood - the movement of the blood shifts the frequency of the light. That change is directly related to the speed of the blood. The pulse changes the speed of the blood, so the display just shows when the speed is changing.
Regarding the pulse-ox device, the light measures how much hemoglobin is hooked up with the red blood cells. That is called the oxygen saturation.
Yeah, they call that a Pulse-ox for the two measurements being made, pulse, and oxygen level in the blood.
chr (author)  Kiteman6 years ago
The point was to make something non-invasive and non-bothersome. Something that is just there, and does its job. I'm not going to strap a microphone or an optical sensor to my body, hehe. I want to make a fully automatic gadget to do this.
Goodhart chr6 years ago
Would something like this Ultra thin condenser mic be useful? Taped over the left side of the chest or, placed "on" one's chest if the sleeper sleeps on their back, it would do an excellent job of picking up "heart beats".

This is, of course, if you wish to monitor the "sound" of the heart. Trying to record a homestyled EKG might be a bit more difficult (not to mention risky).
Kiteman chr6 years ago
Got you. Maybe a sensitive mike suspended over the bed will do the job (no extra bed-frame noises), but it would be a heck of a job to separate other night-time sounds from the breathing, belching, moving etc.
vince776 years ago
Did just this to catch a skipping heart beat that the Holter Monitor from the hospital couldn't catch... Used the microphone out of a cheap desktop mic and turned the gain all the way up in Audacity. Placed the mic over the spot that sounded loudest and compressed it with a towel under a dinner plate. Shows up as pulses but it did the job.
Kiteman6 years ago
I've had a sudden thought - would a seismograph affair work, detecting vibrations in the bed as a whole?
chr (author)  Kiteman6 years ago
aah, great idea! Only problem is that I have to build a seismometer to test if it works, hehe Maybe a digital accelerometer can do the job?
Kiteman chr6 years ago
Not a clue. Does this help:

http://www.silicondesigns.com/1010.html

?
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