SPEAKE(a)R: Turn Speakers to Microphones for Fun and Profit [pdf] (2017)

Post by userbinator » Sun, Apr 19, 2026, 7:37 PM UTC

angg wrote: post #60

Anechoic wrote: post #43

This is how drive-thru kiosks work (principal, not the specific implementation). Source: I used to measure the “microphone” frequency response for a kiosk OEM.

This comment caught me off guard and I couldn't believe this to possibly be true but as it turns out, yes, drive-thru speakers used the *literal same physical membrane* to act as both the speaker and microphone, and this was apparently widely commonpractice as recently as the 90s. And they literally just used off the shelf, bog standard stereo speakers to use as a mic. Insane. Given that such a mic would be several f…

Post by QuercusMax » Sun, Apr 19, 2026, 11:11 PM UTC

VladVladikoff wrote: post #38

When I was a teenager I was friends with an extremely poor kid who literally lived on the wrong side of the tracks. He couldn’t afford a microphone and used an old pair of busted headphones to rap into as a microphone. He had recorded and produced a whole album like this with Fruity Loops on an old computer he found discarded at the side of the road.

Post by m463 » Mon, Apr 20, 2026, 2:54 AM UTC

bigbugbag wrote: post #14

jpc0 wrote: post #10

A magnet in a coil operates both ways, this is non intuitive but perfectly sound. Not sure if it's mentioned in the article but microphones can be speakers too...

same with solar panels, they can be reversed to emit light.

Post by undebuggable » Tue, Apr 21, 2026, 2:16 PM UTC

kQq9oHeAz6wLLS wrote: post #74

undebuggable wrote: post #67

That's all true. As a kid I was watching with sister a children's show in TV. The actor on the screen asked a question followed by silence. My sister yelled the answer at the TV, then the actor said something like "you're right kid". I was flabbergasted.

This also works during televized sporting events. The refs can indeed hear you, but you have to yell pretty loud.