diagrams

pectrum diagrams

Complex waves can be decomposed into the simpler waves that make them up. We're interested in diagraming the frequencies and the amplitudes of these simpler waves.E.g.,





The simple waves that make up the complex wave are:

Component wave	Frequency	Amplitude
A	100 Hz	30 dB
B	200 Hz	10 dB
C	300 Hz	20 dB

We typically diagram these as vertical lines in a graph where the horizontal position represents the frequency of the simple wave and its height represents the amplitude:

This kind of spectrum diagram is especially convenient for naturally occurring waves, which are typically composed of a lot of simple waves. Two examples:
A flute playing middle C: 
 
A bass clarinet playing an A-sharp (two below middle C): 
 
(Sounds and plots for the musical instruments come from Geoffrey Sandell's SHARC Timbre database at Loyola University Chicago.)
Don't confuse these spectrum diagrams with spectrograms (which we'll cover later).