Boom 3D - Audio enhancer with 3D surround sound
PulseEffects - Limiter, compressor, reverberation, stereo equalizer and auto volume effects for Pulseaudio...
Letasoft Sound Booster - Boosts sound volume above maximum level
JamesDSP for Linux - An audio effect processor for PipeWire and PulseAudio clients.
FxSound - Clearer Sound for Your PC. The new FxSound boosts your sound quality, volume, clarity and bass.
Equalizer Pie - Equalizer Pie is a free audio manipulation application for OS X.