# High-pass filtering: highpass

### 15.2.10 High-pass filtering: highpass

The highpass command applies a simple first-order lowpass RC filter to an audio clip.

- highpass takes two mandatory arguments and one optional argument:
  - A, an audio clip or a real vector representing the sampled signal.
  - c, a real number specifying the cutoff frequency.
  - Optionally, r, a samplerate (by default 44100).
- highpass(A,c ⟨ r⟩) returns the input data after applying a simple first-order highpass RC filter.

#### Example.

Input:

f:=unapply(periodic(sign(x),x,-1/880,1/880),x);
s:=apply(f,soundsec(3)):;
playsnd(highpass(createwav(s),5000))

Output:
The sound of the periodic signal after a simple first-order highpass RC filter has been applied.