A triangle wave
is a waveform
that can be obtained by subtractive synthesis
(lowpass filtering) a square wave
|A bandlimited triangle wave pictured in the time domain (top) and frequency domain (bottom). The fundamental is at 220 Hz (A2).|
Like a square wave, the triangle wave contains only odd harmonics
. However, the higher harmonics roll off much faster than in a square wave, and so its sound is smoother than a square wave and is nearer to that of a sine wave
It is possible to approximate a triangle wave by additive synthesis, by adding odd harmonics of the fundamental, rolling them off with frequency faster than with a square wave. The infinite series will converge to a triangle wave.