How to boost volume in Audacity (without clipping)

All four make audio louder, in different ways. Amplify and Normalize raise everything by the same amount until the loudest peak hits a limit. A compressor first squeezes the gap between loud and quiet parts, so you can then raise the whole thing further. Loudness Normalization sets the average loudness to a target, which is what podcast and streaming platforms care about.

Select the audio, then Effect, Volume and Compression, Amplify. Audacity suggests the gain that brings the loudest peak to 0 dB. Leave Allow clipping unticked, and set New Peak Amplitude to about -1 dB to leave a little headroom. To boost only one quiet section, select just that part first. Ticking Allow clipping causes audio clipping, which you can't undo after export.

If Amplify barely helps, a single laugh or cough is probably hitting the ceiling. Apply the Compressor (Effect, Volume and Compression, Compressor) to tame peaks, then amplify again. Settings are in the Audacity compressor guide.

For podcasts and spoken audio, Effect, Volume and Compression, Loudness Normalization, set to perceived loudness, is the most reliable way to land at a consistent level. A common target is -16 LUFS for stereo and -19 LUFS for mono. More detail in how to normalize volume in Audacity.

Hilite applies loudness normalisation to every episode so quiet and loud speakers end up at the same level. For a single file, try the free audio normalizer.