ferraus dehiss

Reduce broadband hiss

Synopsis

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

Estimates a per-frequency noise floor from the quietest frames (or uses the level you give), then applies a soft spectral gate restricted to --range: bins near the floor are reduced by --reduction, bins well above it pass, with a --transition-wide soft knee in between. Gains open quickly and close slowly to avoid 'musical noise'. A --range ending at 20 kHz or above extends to Nyquist.

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

Examples

Measure the hiss and reduce it by 12 dB

ferraus dehiss tape.wav -o clean.wav

Stronger reduction, above 3 kHz only

ferraus dehiss cassette.wav --reduction 18dB --range 3kHz..20kHz -o clean.wav

Gentle reduction against a known hiss level of -66 dBFS

ferraus dehiss narration.wav --floor -66dB --reduction 8dB -o clean.wav

Only above 5 kHz, with a wide soft knee to keep cymbals natural

ferraus dehiss vinyl.wav --range 5kHz..20kHz --transition 10dB -o clean.wav

Options

Flag	Type	Default	Meaning
`--floor`	text	`auto`	Hiss level as dBFS RMS (-60dB) or 'auto' to measure it from the quietest frames
`--reduction`	gain	`12dB`	How far hiss-only bins are lowered, in dB
`--range`	text	`2kHz..20kHz`	Frequency range the gate acts on (low..high, e.g. 2kHz..20kHz)
`--transition`	gain	`6dB`	Width in dB of the soft knee between full reduction and none
`--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_dehiss
Schema: ferraus schema dehiss
Pipeline: { op: dehiss, args: { ... } } (flag names with _ instead of -)
fx stage: yes

{"command": "dehiss", "defaults": {"floor": "auto", "reduction": "12dB", "range": "2kHz..20kHz", "transition": "6dB", "mix": "100%"}}