I disagree. Despite its name, the “Leveler” effect is a terrible way to level out the volume. The “Leveler” effect reduces the dynamic range by distorting the waveform. If it is set high enough to have a significant “levelling” effect, then it also produces noticeable distortion.
A better option is to use the “Limiter” effect (Limiter - Audacity Manual) with the “Type” set to “Soft Limit”.
If a stronger amount of volume adjustment is needed, then either:
- Adjust the level manually with the envelope tool (better option, but fiddly and time consuming) Envelope Tool - Audacity Manual
- or for automatic adjustment, try this “AGC” plug-in: AGC - Automatic Gain Control
Instructions for installing the optional AGC plug-in (and any other "Nyquist plug-in) can be found here: Effect Menu - Audacity Manual