“What’s fascinating about this is the importance of the transient to our ability to distinguish sounds”

Paul McGowan writes:

I mentioned recently that we recognize what type of instrument is playing a note not so much by its harmonic content – which most of us believe is what distinguishes the sound of one instrument from another – but rather by its transient nature.  I think this is a fascinating subject and intend to explore it to see where it leads.

Surprisingly it is the beginning of the note being played that tells us what type of instrument we are listening to.  Certainly the harmonic content of the played note as well as its amplitude envelope are important – but only after our ear/brain mechanisms identify the start pattern of that note.

Multiple studies have been conducted where the beginning of a played note has been chopped off in a recording – then played back to a listener in a controlled environment.  Interestingly enough, even if we have two very dissimilar instruments, perhaps a trombone and a cello, if the listener goes back and forth between the two recordings of each instrument playing the identical note – sans the natural start and stop of that note – it turns out to be very difficult to tell the difference between the two instruments.

What’s fascinating about this is the importance of the transient to our ability to distinguish sounds.  The beginnings of this are obvious from an evolutionary perspective and stem, no doubt, from our desire to not be eaten by some beast in the wild.  Think about the sound a lion or tiger makes.  Taken as a simple steady tone, you’d be hard pressed to know it was a lion making the noise – but now add in the beginning and ending transients of the lion’s roar and it’s obvious to us what the sound represents.

It is no different from that of the beginning touch of the bow on a violin – it’s the transient that we instantly recognize as a unique identifier – the sustained note itself less informative as a pattern.

We are, after all, pattern recognizing creatures – as are all sentient beings – but our ability to project multiple future patterns that have never existed is what truly separates our lot from the rest of the animals.  We call it imagination and when our imaginations create repetitive frequency based patterns we call that music.  If those patterns resonate with our expectations or delight us with new agreeable patterns – we call that “liking the music” and we enjoy repeating the patterns over and over again.

Central to these patterns are the start/stop transients and how well our systems handle those patterns has a lot to do with how they sound.