Captions turn speech into text — Computing, 4–6
A computer can listen to speech and show words on the screen, though it can make mistakes.
Words can appear as someone speaks
Captions are written words that match speech in a video or conversation. A computer listens for sounds, guesses which words they make, and puts those words on the screen. Captions may also show important sounds, such as [door closes].
Why are captions useful?
Someone may not hear the speech clearly, may be learning the language, or may be somewhere that must stay quiet. Written speech gives another way to follow what is happening. The problem is not always the speaker; sometimes the sound cannot be heard or understood easily.
Making a caption
Imagine someone says, “The red ball is under the chair.” First, the microphone receives the voice. Next, the computer matches the sounds to words. Then it displays “The red ball is under the chair.” If a cough covers “red”, the caption may miss or change that word.
Captions can be wrong
It is reasonable to trust every caption because the words look neat and official on the screen. But the computer is guessing from sound, not understanding the whole meaning like a person. Accents, fast speech and background noise can produce a funny or completely different word.
Captions outside school
You see captions in videos, on live television and during some video calls. They help when a baby is sleeping, a train is noisy, or a viewer hears differently. A person can also add captions to a video so more people can follow the message.
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