Three tone controls and a set of presets that fix the usual problems: too boomy, too thin, too harsh, too muddy.
If a boost pushes the file past its maximum level it is brought back down automatically, so the result never distorts.
An equalizer turns parts of the sound up or down depending on their pitch. This one keeps it to three controls, which is enough to fix nearly every everyday recording problem.
Bass covers the low rumble and body below about 200 Hz — boost it for weight, cut it when a recording booms. Middle is where voices live, around 1.2 kHz; lifting it pulls a speaker forward out of a muddy room. Treble is everything above 4 kHz: air, detail and sibilance, which you lift for clarity and cut when a recording is harsh.
Two extra switches handle the problems a tone control cannot. Cut rumble removes the sub-bass thud of traffic, air conditioning and desk knocks without touching the voice. Cut hiss rolls off the very top where tape and cheap-microphone noise sits. There is also an optional levelling pass that pulls the loud parts down and the quiet parts up, which is what makes a podcast comfortable to listen to in a car.
Bass is the low end below roughly 200 Hz — weight and boom. Middle sits around 1.2 kHz where most of a voice lives. Treble is above 4 kHz — brightness, detail and hiss.
Because a boost that would push past the maximum is brought back down automatically to stop it distorting. If you want it louder overall, use the Volume Changer afterwards.
It applies a compressor: the loudest moments are pulled down and the whole thing is then raised, so the quiet parts come up with it. It is what makes podcast audio listenable at low volume.
Only when the noise sits somewhere the voice does not — rumble below 80 Hz, or hiss right at the top. Noise spread across the same range as the voice cannot be removed by an equalizer.
Beyond about 6 dB on any one control things start to sound processed. Cutting what you do not want usually beats boosting what you do.