# how can we hear people’s voices through a phone? How can our voices travel across the world through a mobile?

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how can we hear people’s voices through a phone? How can our voices travel across the world through a mobile?

In: Technology

Voices are sound waves. A sound wave is a change in air pressure, and you can describe all the information in a sound wave by describing the change in pressure over time.

To make voices into electricity in your phone, you put a diaphragm near an electromagnet. When you talk, the air pressure makes the diaphragm move, and that makes electricity in the electromagnet. Now, instead of a change in pressure over time, we are dealing with a change in voltage over time.

If you hook the electromagnet up to wires, and hook those wires up to a computer, you can convert the changing voltage into a series of numbers. This is a better way of recording sound, because once you have numbers, you can design error-correction techniques to ensure you don’t lose any data. If you have trouble connecting one computer to another, you can store the numbers and resend them later, etc. Putting it in numbers gives you flexibility.

Now that you have the voice recorded in numbers, you need to convert it again: this time, into a radio wave. This is also voltage over time, but instead of electrons in a wire, it is electromagnetic waves through space. Those waves go from your phone to a cell tower and are converted back into numbers. Then they may be converted into waves again, or put back over a wire. Either way, the numbers are broken up into groups called packets and put back together once they get to their destination. This is so each packet can choose the best route to the destination, instead of the whole message having to follow the same route. This makes things faster.

At the destination, the whole process runs in reverse: radio waves or voltage on a wire back into numbers again. Then numbers back into radio waves from another cell tower, which are picked up by the other person’s phone, and turned back into voltage on a wire. The voltage on a wire is hooked up to a diaphragm next to an electromagnet – it looks a lot like the microphone you spoke into, but is designed a little differently. This time, the electromagnet moves the diaphragm, and the diaphragm pushes on the air to replicate the sound of your voice.