ferraus notch

Narrow notch filter, optionally with harmonics

Synopsis

ferraus notch <input> [options] [-o <output>]

Cuts a narrow band around --freq by exactly --depth at the centre (and returns to unity away from it). --harmonics adds that many notches at integer multiples of the frequency. dehum is the tuned, self-detecting version for mains hum.

This command is also an fx stage and a pipeline op: ferraus fx in.wav -o out.wav --fx "notch:key=value".

Examples

Remove a 1 kHz whine

ferraus notch in.wav --freq 1kHz -o out.wav

Deep notches at 60, 120, 180, 240, and 300 Hz

ferraus notch in.wav --freq 60Hz --harmonics 4 --depth -60dB -o out.wav

Remove the 15.75 kHz whine of an old CRT television

ferraus notch lecture.wav --freq 15.75kHz --q 50 -o lecture_clean.wav

Tame a booming resonance at A1 (55 Hz) by 12 dB with a wider notch

ferraus notch bass.wav --freq A1 --depth -12dB --q 10 -o bass_notch.wav

Options

Flag	Type	Default	Meaning
`--freq`	frequency	`60Hz`	Notch centre frequency (Hz, kHz, or a note name)
`--q`	number	`30`	Quality factor (centre / bandwidth); higher is narrower
`--depth`	gain	`-40dB`	Attenuation at the centre in dB
`--harmonics`	integer	`0`	Additional notches at 2x, 3x, ... the frequency Range: 0..64.
`--mix`	percent	`100%`	Dry/wet balance: 0% returns the input unchanged, 100% is fully processed

Global options

Every command also accepts the global options (-o, --json, --dry-run, --overwrite, --progress, ...). See Global options.

Exit codes

Code	Meaning
0	Success
1	Processing failed
2	Usage or parameter error
3	Input missing or unreadable
4	Unsupported format or codec
8	Cancelled
70	Internal error (bug)

Common mistakes

Forgetting that outputs are never overwritten: pass --overwrite or a new -o path when re-running.
Gains need a unit when not in dB: 0.5x is a factor, -6 and -6dB are decibels.

For models

MCP tool: ferraus_notch
Schema: ferraus schema notch
Pipeline: { op: notch, args: { ... } } (flag names with _ instead of -)
fx stage: yes

{"command": "notch", "defaults": {"freq": "60Hz", "q": "30", "depth": "-40dB", "harmonics": "0", "mix": "100%"}}