Digital sound — Computing, 7–10
A computer cannot store a moving sound wave directly, so it measures the wave many times and records the measurements as numbers.
Sound becomes numbers
When you speak, air vibrates in a pattern that your ears can hear. A microphone turns that vibration into an electrical signal, and a computer measures the signal again and again. The measurements become a list of numbers; when a speaker follows those numbers, it makes the air vibrate in a similar pattern.
Why measure sound?
Computers work with numbers, but sound in the real world is a continuous wave, like a smooth line. Measuring it lets computers record, copy, edit and send sound using the same kind of information they use for other digital work. The challenge is choosing enough measurements to keep the important shape without making every recording enormous.
A tiny recording
Suppose a very simple sound is measured four times, and the microphone gives 2, 5, 3 and 1. The computer stores those four numbers in that order. To play the sound, the speaker moves according to 2, then 5, then 3, then 1. Real recordings use thousands of measurements each second, so they sound much smoother than this example.
A recording is not the wave itself
You may imagine that a recording contains the exact sound wave, frozen inside a file. It actually contains samples: separate measurements taken at particular moments. If there are too few samples, quick changes can be missed and the sound may become rough or inaccurate. More samples usually preserve more detail, but they also need more storage.
Sound all around you
Voice messages, podcasts, songs, audiobooks and video calls all turn sound into digital measurements. Editing software can cut silence, change volume or join two recordings because it is working with those numbers. A microphone and speaker then connect the digital world back to the moving air that your ears hear.
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