Sound is vibration — Music, 14–17 years
How vibrating air, strings and surfaces become the sounds we hear in music. Music, 14–17 years.
What sound is
When a guitar string moves back and forth, it pushes the nearby air in repeating waves. Those waves reach your ear and make your eardrum move, so your brain hears a note. Faster vibrations sound higher; slower vibrations sound lower.
Why vibrations matter
This idea solves a puzzle: how can something invisible travel from a speaker to your ear? Musicians need it to control pitch, volume and tone colour. A note’s frequency sets its pitch, while the size and shape of the vibration help give a piano and a flute different sounds.
Worked example: an octave
A tuning standard gives the note A4 a frequency of 440 hertz, meaning 440 vibrations each second. The A one octave above has twice the frequency: 440 × 2 = 880 hertz. It sounds higher, but the two notes still feel closely related because their vibration rates have a simple 2:1 ratio.
Trap: loud means high
A common mistake is to think a loud note must also be high. It is reasonable, because a louder vibration is bigger and can feel more powerful. In fact, frequency controls pitch, while amplitude mainly controls loudness, so a low drum can be loud and a high whistle can be quiet.
Where it appears
This appears when instruments are tuned, microphones record performances and speakers reproduce them. Engineers measure frequencies to remove unwanted feedback or make headphones sound balanced. It also explains why a room, a concert hall and an open field can make the same instrument sound different.
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