The noise profile
Select a second where only the room is heard and press N (Use as noise): the editor learns what the noise sounds like from that time. Process → Reduce noise then takes it out of the selection, or of the whole project when nothing is selected. A profile carries a steady noise, mains hum at 50 or 60 Hz, a fan, a hiss; it does not carry a noise that changes.
The pauses
Truncate silence (Shift+T) finds the pauses quieter than a level and longer than a time, and shortens each, keeping half at each edge so that the two halves meet once the middle is taken out. Shorter quiet stretches are left alone: they are the rhythm of speech.
Quiet and loud
Process → Leveler raises the quiet passages and lowers the loud ones, by a Target and an Amount. It first listens for the room, and once the last word of a phrase ends the gain holds instead of climbing, so a pause is not raised to the voice's level; words barely louder than the room are held with it. It is heard at once, and Ctrl+Z takes it back.
The target
The readout beside the master shows the short-term and integrated loudness and the true peak. Process → Normalise sets the selection to a peak, or to a LUFS target, in one step; the readout then says where it sits.
What a pass cannot fix
A noise that changes, traffic, a second voice, music under the speech, is not a profile and is not taken out. A recording that reached full scale is clipped: Analyse → Find clipping marks each clipped stretch as a region, but the lost signal is not put back. Two voices on one track are levelled together, not apart. Each pass renders the audio anew into the project, which is what makes it one undo step, and a pass applied twice is twice the change.
Questions
- Can I remove background noise from a podcast online?
- Yes: select a second of the room alone, press N, then Process → Reduce noise. The pass is one undo step.
- Which comes first, noise or level?
- Noise first. The Leveler would raise the noise in the quiet passages along with the voice; with the noise gone, it raises the voice alone.
- What is LUFS?
- A measure of loudness as heard, over the whole recording, not of its peaks. Podcast platforms state their target in it, and Normalise in Process sets a recording to one.