gray = even-numbered harmonics
, (1
f
), 2
f
, 4
f
, 6
f
..., e.g. triode valve (tube)
and
white = odd-numbered harmonics
, 1
f
, 3
f
, 5
f
..., e.g. organ pipe closed at top
and clarinet
all integer harmonics
, e.g. saw tooth wave.
The frequency spectrum of a symmetric
square wave signal
(pulse-pause ratio of
1:1) has exclusively odd-numbered harmonics of 3, 5, 7… or even-numbered
overtones 2, 4, 6…
The sound spectra of clarinets tend to have strong odd harmonics (fundamental, 3rd,
5th, 7th etc) and weak even harmonics (2nd, 4th, 6th etc), at least in their lowest
registers.
Tympanic membranes or bells have a large number of individual vibrations, which are
not simply the exact multiples of single fundamental frequency.
These are not harmonic overtones and are often called partial tones or partials.
Overtones whose frequencies are not an integer multiple of the fundamental are called
inharmonic and are often perceived as unpleasant. Inharmonics are not the same as Enharmonics. Bells have more clearly perceptible
partials than most instruments.
An "exciter" is a special equalizer, which creates new overtones. The processed
signal is added to the original input signal.
|