Re: Playing nearer the bridge - louder or just different?

It can be both.

When you pluck it, most of the force of the string's vibration goes
into pushing the bridge and top in and out, like a speaker cone,
assuming you plucked the string so that it's moving 'vertically'
relative to the soundboard. If you look at the wave form of this
'transverse' force, it's initially a square wave, with a 'duty cycle'
that depends on where you pluck the string. That is, if you pluck the
string 1/5th of the way up its lenght from the bridge, the force will
be 'down' at a low level for 4/5ths of the time, and 'up' at a higher
level 1/5th of the time. (There is a tension change force, causing the
bridge to twist toward the neck twice for every up-and-down cycle, but
it's usually much lower)

If you look at the spectrum of the transverse wave, it will have a
certain amount of energy in the fundamental, and less in each partial
up to the fifth one, which is missing. Then there will be some energy
in the 6th partial, more in the seventh and eighth, and less in the
ninth, with the tenth partial missing. I think you can see the
pattern.

As you pluck closer to the bridge you start out with more and more
energy in upper partials, and fewer and fewer missing ones. I'll
note that with nylon strings the higher frequencies die out fairly
fast, due to the nature of the strings, but the 'attack' part of the
sound certainly will have more high frequency energy. Since your ears
are generally more sensitive to high frequencies than lower ones, even
if the total amount of energy in the pluick is the same, it will
probably sound 'louder'.

As has been pointed out, it takes more force to displace a string a
given distance when you play closer to the bridge. This means you can
pluck the string harder when you play sul ponte, and put in more
energy. So, all else equal, there may not be more power available, but
often people do play harder close to the bridge.

Alan Carruth / Luthier
.

Relevant Pages

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