Tuesday, March 15, 2022

Beats By Ben | Building and Using a Digital Stethoscope

Since 2018, I've had on my Blog Ideas List the topic of recording heart sounds. Mind you, this isn't for any practical purpose; my Garmin watch has me covered in that department. Instead, the motivation was to record one of life's greatest miracles: the always-on, never-tires heart that sustains us all.

When I initially had the idea, I watched a few random videos on YouTube and found a reddit thread on the topic, but none of these resources left me with an obvious path forward.

I recently revisited the idea and was surprised to see a number of new videos on YouTube that were exactly what I was looking for. One tutorial was from two electrical engineers in Israel, and the other was from an ER doc in Toronto. Both videos described how you could cheaply capture heart and lung sounds, and both had the same motivation: to offer low-cost telehealth tech for the Covid-19 pandemic.

In the US, at the moment things are looking fairly stable from a Covid-19 perspective. We've got access to vaccines, high quality masks and promises of additional Covid treatments on the way. When these videos were published, the situation was far more fluid and dire. There was a very real fear that hospitals would be overrun and low-cost, hacky solutions for doing telehealth may very well have been a game changer.

In short, I look at these videos as more than How-Tos. They're the medical community thinking on its feet and MacGyvering solutions in real-time, and it's amazing.

The approach that both the Israeli Team and the Doctor from Toronto recommend are essentially the same. Get a cheap stethoscope and cheap microphone. Cut the tubing of the stethoscope a couple of inches away from the bell. Jam the microphone into the tubing and secure it. And you're done.

The microphone, once plugged into your cell phone, can be used in any video conferencing or audio recording app. Doctors could listen to heart sounds in real time in a Zoom-like session or have patient e-mail samples to them.

I purchased a $6.95 stethoscope and a $10.99 lavaliere microphone from Amazon. I cut the tubing, and unscrewed the microphone to remove the housing. Initially I used mounting putty to secure the microphone in place. I quickly swapped that out for Sugru, which is a more durable and permanent solution.

I recorded the following clip on my Galaxy S10+ by using the built in voice recorder app and plugging the microphone into the headphone jack. I messed with the audio a bit in Audacity, though I have little clue as to what I'm doing there. The first clip is the original version of the recording, the second clip uses Audacity's 'Noise Reduction' effect to clean things up.

As you can hear, it works! The sound quality is far from perfect, but you can definitely hear a steady heartbeat. In the version without noise reduction, you can hear breath sounds, too.

The screenshot below of Audicity shows the wav form of the audio I collected. It even looks like the heartbeat pattern you see in the movies. That's to be expected, but it's still cool to see.

I'm not entirely sure how I'm going to put my $18 digital stethoscope to use. But I'm psyched to add a media capture tool to my toolbox, especially one that let's me record phenomena that are typically undetectable.

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