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Topic: Clipping after reducing some frequencies with EQ? (Read 221 times)
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## Clipping after reducing some frequencies with EQ?

##### 2020-11-02 18:27:26
Usually, clipping appears only if EQ is used to boost frequencies. But i found sample where clipping appears after reducing frequencies with EQ. For example, using EQ in Audacity to reduce high frequencies leads to clipping. I also tried other EQs and results are similar.

Can someone explain why exactly is this happening? The sample is short piece of Ananga-Ranga from Merzbow - Venereology.
https://www.dropbox.com/s/e7qqv1fg91be8pv/01.%20Ananga-Ranga.flac?dl=1

## Re: Clipping after reducing some frequencies with EQ?

##### Reply #1 – 2020-11-02 18:40:10
This is easy to explain:

A Square wave is a wave that has a fundamental frequency and then several harmonics.
https://en.wikipedia.org/wiki/Square_wave

Those harmonics convert the sinusoidal fundamental frequency, progressively into a square. See the image in that wikipedia article, near the bottom, where it shows the conversion of a sine into a square.
What you will also see in that image is that the top of the sinus is higher than the top of the square.

Given that Merzbow is a kind of genre where saturation and compression is used a lot, it would be somewhat logical that filtering higher frequencies could increase the peaks.

## Re: Clipping after reducing some frequencies with EQ?

##### Reply #2 – 2020-11-02 18:41:02
This is easy to explain:

A Square wave is a wave that has a fundamental frequency and then several harmonics.
https://en.wikipedia.org/wiki/Square_wave

Those harmonics convert the sinusoidal fundamental frequency, progressively into a square. See that animated image in that wikipedia article, near the bottom, where it shows the conversion of a sine into a square.
What you will also see in that image is that the top of the sinus is higher than the top of the square.

Given that Merzbow is a kind of genre where saturation and compression is used a lot, it would be somewhat logical that filtering higher frequencies could increase the peaks.

## Re: Clipping after reducing some frequencies with EQ?

##### Reply #3 – 2020-11-02 18:52:27
Most filters (all filters?) have some ripple (frequency response variations) in the passband.

The slight clipping probably isn't audible, and Audacity uses floating-point internally so it's not actually clipping it's just going over 0dB and audacity is showing you potential clipping.  If you are a perfectionist you can use the Amplify or Normalize effect to bring the volume down so you don't get a clipped file when you export (or when you play it).

## Re: Clipping after reducing some frequencies with EQ?

##### Reply #4 – 2020-11-02 20:10:21
If you have peak normalized and highly compressed audio, some clipping is normal when low pass filtering it because the new waveform will have peaks that were not present in the original.

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