# Highpass filter square wave

Generated a 1kHz square wave in Audacity and normalized it to 0dB (fs = 44100Hz):

Added a 24dB/oct high pass filter (std Audacity plug-in), cutoff frequency set to 100Hz. Result:

Zoomed version:

EDIT: When normalized to -3dB before filtering there's no "clipping" present.

Filtering same signal with low pass filter does not have this issue.

• If you reduce the level of the input, does that eliminate the clipping? Jul 12, 2020 at 11:30
• Why don't we see those dots that show the actual values in the 'clipped' range? Could it be that the values aren't really clipped but that they are just outside the plot range? It's perfectly possible that the initial value of a high pass filter's step response is greater than $1$. Jul 12, 2020 at 12:39
• Here's how it looks in some other implementation: i.postimg.cc/cCyD3yDs/file.png ... so, it's not Audacity issue in question. Jul 12, 2020 at 12:47
• @MattL, Ok, changed the images... . Jul 12, 2020 at 16:07
• I don't see any clipping anymore. Of course, the maximum amplitude is increased but that's not so strange. Jul 12, 2020 at 16:25