Paul McGowan: Pluck or strum a stringed instrument and you get sound from the vibrating strings amplified by the attached hollow box. As we have mentioned earlier the sound of that plucked string depends certainly on the type of string, its length, tension and sound of its mechanical amplifier, but more so on how that note begins and ends its vibrations.
Take the sound of any two instruments playing the same note and remove their starting and stoping information from the recording and most people would have a hard time telling what instrument was playing the note; despite the fact the two instruments are so darned far away from each other’s sonic signature.
The pluck of the string or the beginning air movement of a wind instrument is called a transient and the ending notes a decay. Transients contain perhaps the single most important information for us to process when our ear/brains identify what the nature of a particular sound is, the decay simply gives further verification that our choice was correct.
Transients are also the most difficult audio stimulus for both electronics and loudspeakers to get right. If you’ve ever wondered why reviewers and designers take the time and effort to test audio products with sophisticated lab equipment usually always include what’s known as an impulse response – it is these transients they are concerned with. Why?
Because when you stimulate a microphone, speaker driver, amplifier or anything audio related you get more than you bargained for – and when you get more out of an audio system than what you put in – that’s called distortion.
The nature of stimulating a physical object results in what we call ringing – tap your fingernail on a wine glass and what happens? It rings – as you’ve actually bent the glass slightly and it is vibrating back and forth as it tries to regain its original shape. The same can be said for an audio circuit. When you stimulate it with a fast moving impulse – which is nothing more than a movement from the zero resting state to something higher in quick fashion – the circuit or transducer will ring, adding unwanted energy to the music.
Tomorrow we’ll “ring in” some music for you.
