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# Tame harsh high frequencies with lowpass
- URL: https://ffmpeguru.com/tame-harsh-high-frequencies-with-lowpass/
- Published: 2026-09-07T09:00:00.000Z
- Updated: 2026-10-13T17:59:42.000Z
- Author: FFmpeguru
- Tags: ffmpeg

The mirror of the highpass filter, \`lowpass\` removes everything above a cutoff frequency. It is the right tool for taming sibilance, hiss, and high-frequency noise that survived the denoiser. It is also a quick way to make a recording sound 'warmer' without changing the overall level.

## The command

```
ffmpeg -i in.wav -af "lowpass=f=12000:poles=2" out.wav
```

## What it does

The filter passes everything below the cutoff and attenuates everything above. \`f=12000\` sets the cutoff to 12 kHz. A 2-pole filter is gentle; a 4-pole filter is steeper. For a voice recording with sibilance, start at 8 kHz; for a music track with harsh cymbals, 12 kHz; for a clean vocal, leave the default (off).

## Requirements

Any audio input. The filter is in libavfilter. CPU-only, single-pass. The filter is mono by default; for stereo, pass \`lowpass=f=12000:channels=stereo\` or run two instances.

## Things to avoid

- Setting the cutoff below the sibilance range. Sibilance is between 5 kHz and 10 kHz; setting the cutoff to 4 kHz will muffle the entire recording.
- Using a very steep slope. A 4-pole filter introduces ringing at the cutoff; start with \`poles=2\` and use a higher pole count only when the sibilance is severe.
- Combining lowpass with a denoiser that already removed the high-frequency noise. The lowpass will further dull the recording without changing the perceived noise.
- Replacing a parametric EQ. The lowpass is a single slope; a parametric EQ lets you cut a narrow band without affecting nearby frequencies.