[sdiy] Amplifying Pulse (Slightly OT)
gordonjcp at gjcp.net
Fri Aug 10 11:23:00 CEST 2018
On Thu, Aug 09, 2018 at 07:19:28PM -0400, Busby Bergson wrote:
> Hi all -
> Sorry for the question, it's not exactly "synthesizers" - but a friend
> of mine would like to amplify the sound of his pulse, from the wrist.
> Contact mics wouldn't cut it. I thought people here might have
> considered some interesting approaches to this concern.
Your pulse doesn't make any sound. You can feel a slight flexing of the
radial artery when you take your pulse at your wrist, but it's way too
small and slow to make any noticeable sound.
When you measure blood pressure with an old-fashioned sphygmomanometer
you're listening for blood scooshing through the brachial artery as the
air bladder in the cuff squeezes it shut. You pump it up until the
noise stops (artery closed) then release the pressure until you just
start to hear it hiss through which gives you the systolic pressure, and
slowly release it some more until you just hear it as a faint tapping
for the diastolic pressure.
Automatic sphygs use the change in pressure in the bladder to measure
it, apparently. I've never had one apart.
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