The CIA…plug a set of regular headphones into a microphone jack, open a recording application and speak into the headphone speaker, you don’t need a 3 letter agency for that physics open secret.
I got this clone Apple lightning to 3.5mm headphone jack adaptor for iPhone, my mind was kinda blown when I found out it just uses the lightning for power and inside the plug is a tiny bluetooth device that stream music over the 3.5mm jack. The original adaptor doesnt work like this as far as i have considered.
Wouldn't you need to rewire the headphones? Headphones use a 3-pin TRS whereas a 4-pin TRRS plug is used when you add a microphone. Regardless if the 4-pin is CTIA or OMTP, it's generally only going to get shorted to ground if a 3-pin TRS plug is plugged into a 4-pin TRRS socket, or if a 4-pin TRRS plug is plugged into a 3-pin TRS socket.
This is basic physics controlling the effect here, not electrical routing. Speakers are microphones by their very design. To make them work as a microphone, you merely speak into them with them plugged into an input jack that provides at minimum a line level electrical signal to be modified by wiggling the speaker cone/diaphragm back and forth.
Yes, but the computer doesn't have the firmware to "record" that signal from the speaker output pins. Thus, to record from the speakers acting like microphones, would require rewiring the headphone cable, for the vast majority of computing devices.
If you click "record" on your computer, there's no way to tell it to record signal from the speaker output channels, even if you write a custom low-level application directly making OS calls. The OS can't even do it, because it's not supported by the firmware.
"Yes, but the computer doesn't have the firmware to "record" that signal from the speaker output pins."
No, you plug directly into the microphone jack, that is what is providing your line level reference signal that gets changed by motion in the diaphragm. Zero rewiring required.
I am crap with physics but was going to say I think the last 50+ years of speaker development has been about making them less a microphone than they inherently are.
Dynamic loudspeakers and dynamic microphones are the same thing. They always have been the same.
They've got the knobs for the design variables turned in different directions, but they're still the same.
They even have the same frequency response whether they're being used as speakers or microphones at the moment.
Which brings up a valid way to measure the response of a microphone's design:
Use two of them. One as a speaker, and the other as a microphone. Play measurement-sounds out of one, and record the results on the other. Plot it out.
The deviations are magnified, but eliminating that magnification is just a math problem -- not an instrumentation problem. :)
They transmit sound. Anything able to detect the vibrations make it a microphone. Not sure how a speaker gets around that because it’s job is to vibrate.
