### 5.23.4 Low-pass filtering : lowpass

lowpass takes two or three arguments: a real vector v representing the sampled signal, a real number c specifying the cutoff frequency and optionally a samplerate (which defaults to 44100). This implementation is an emulation of a simple first-order lowpass RC filter.

For example, input :

f:=unapply(periodic(sign(x),x,-1/880,1/880),x);
s:=2`^`14*(apply(f,soundsec(1)));
playsnd(lowpass(s,1000))