Does using a phone to call someone technically make sound travel faster than the speed of sound?
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No, because the sound isn’t actually travelling.
When you speak into the phone, you are making sound, which is waves of pressure in the air like ripples in a pond. The microphone has a diaphragm which is moved back and forth by those pressure waves; this movement is measured and converted into an electric analog signal. That means if you took a sound pressure meter in front of the mic, and a voltage meter connected to the mic, you’d see the same waves in both sound and voltage.
Once this conversion happens, there’s no more sound. The sound bounces around the room a bit but that’s it. What’s used is that electrical signal from the microphone. It’s captured by a chip in your phone, which encodes it into digital data. This is done by measuring the voltage many thousands of times per second, and at each measurement assigning a number to the voltage level. So those numbers then represent positions of the diaphragm over time, and thus the sound you are making.
The numbers get compressed and transmitted over the cell network or over a computer to the person on the other end. They may be many thousands of miles away, and may travel over a number of different communications paths such as radio (wireless/WiFi/cellular), copper (Ethernet/landline), fiber (long haul links or Internet backbone), etc.
But however they travel, the numbers arrive in your friend’s phone. The friend’s phone has a voltage generator, and you feed it those numbers, so many thousands of times per second it adjusts the voltage it’s creating. This output goes into a speaker- a cone that can be moved back and forth by applying voltage to a coil. So by feeding the numbers from the microphone’s voltage detector into the speaker’s voltage generator, and feeding that output to the speaker, you make your friend’s speaker cone move in and out in the same pattern as your microphone’s diaphragm.
And thus, when you speak, your friend can hear it- because the sound wave is reproduced. (I’ve left out a few steps, but that’s the important parts).
However, between your mic and your friend’s speaker, there’s no sound. There’s just numbers being sent from one device to another. And thus, sound isn’t travelling, rather, an entirely new sound is being created. It just happens to resemble the old sound.
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