CoachA vibration is a very fast trembling — a back-and-forth movement repeated many times each second, often too fast for the eye to follow. A plucked guitar string vibrates: you see only a blur, but your fingertip feels the buzzing.
Examples
Example 19.5 (Sound sources everywhere)
Hunt the vibration behind each sound: the guitar — plucked strings tremble; the drum — the struck skin trembles; your voice — two little folds in your throat tremble as air from your lungs rushes past (that is the buzz your fingers felt); the buzzing fly — its wings tremble hundreds of times a second; the slammed door — the whole door and its frame shudder for a moment.