How does sound travel over cables?

There are actually two answers to this question, depending on how the device you’re using to generate the sound works. Let’s start with traditional devices, such as a simple microphone to a loudspeaker. 

In this example, the audio is converted from pressure waves in the air to electrical current which runs down a wire. At the other end, that current is converted back into sound by the speaker. This is how sound travels through headphones, amplifier cables, and loudspeakers. The sound is converted into electrical current in the microphone by a diaphragm attached to a magnet inside a coil. The diaphragm vibrates when the sound waves hit it, which also vibrates the magnet. Because the magnet is inside the coil, the vibrations generate current; the variations in the current match the sound waves, so when the speaker picks up the current, it generates a sound that matches what the microphone picked up. 

However, modern technology has provided an alternate way for sound to travel over cables. In this method – such as if you were to send an MP3, AAC, WMA or FLAC file format from one computer to another via an ethernet cable – the audio signal which is converted into electronic signals is then converted again into digital form via a process called sampling. That sample, as with all other data, is then converted into binary signals when it is transmitted down a cable; when it arrives at its destination, it is converted back into the sample, which is then converted back into the electrical signals that a loudspeaker or headphones can convert into sound that we hear. 

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