Reduce noise
What Reduce noise actually does
Noise reduction is a measurement problem wearing the costume of a button. A reducer that assumes a fixed noise floor either scours a clean recording or barely touches a noisy one, and because the only feedback is a downloaded file, nobody finds out which happened. This tool measures the level of a passage that contains nothing but the noise, hands that measurement to the filter as its noise floor, and reports the number on screen. The amount of reduction stays a separate control, because how loud the noise is and how much of it to remove are different questions.
How to use it
- Choose an audio file. The waveform is drawn locally and nothing is uploaded.
- Point the sample window at a passage that is only room tone, hiss or hum, using the start and length fields.
- Set how many decibels of reduction to apply, then run.
- Read the measured noise floor on the result, and switch the player between source and result to hear the trade.
Useful for
- Cleaning air-conditioner or computer-fan hiss off an interview recorded in a room.
- Reducing tape or preamp hiss on a digitised cassette or minidisc transfer.
- Checking how much reduction a recording tolerates before the voice starts to sound processed.
Limits worth knowing
- The sample window must contain only noise. Pointed at speech, it measures the speech and treats it as the floor.
- Spectral reduction removes noise that overlaps the voice by attenuating shared frequencies, so a heavy setting audibly thins the recording. The comparison exists so that is a decision rather than a surprise.
- This is a filter, not a speech model; it does not separate a voice from a competing voice or from music.
- A source with no quiet passage anywhere cannot be measured honestly, and the tool says when the window could not be read instead of assuming a value.
Questions people ask
Is the file uploaded?
No. The measurement, the filtering, the waveforms and the playback all happen in this tab. The audio engine is fetched once and cached.
What does the measured noise floor mean?
It is the average level of the sample window in decibels, and it is handed to the filter as the level below which audio is treated as noise.
How much reduction should I use?
Start at the default and raise it until the result begins to sound hollow, comparing against the source each time. There is no correct number for every recording.