Increase MP3 Volume

Some, if you push too far — that is physics, not software. The built-in limiter catches peaks above the threshold so moderate boosts (150–250%) usually sound clean. Above 300% the quiet parts get loud but the peaks start to pump; use your ears.

Up to 400% of the original, which is about +12 dB. That covers most quiet recordings; a 3-minute file exports in a second or two either way.

No. Normalizing raises the whole file so its loudest peak hits a target level. Boosting here multiplies the level you choose, which is more predictable when you know a recording is uniformly quiet.

Yes. Select the quiet section on the waveform, set the mode to Keep selection, and export — you get just that part at the new volume.

Often, yes — browsers can usually decode the audio track of MP4 files dropped onto the page. If your browser refuses the file, extract the audio first and try again.