How changing volume works on a file
Changing volume on a file means multiplying every audio sample by a number. Multiply by 2 and the signal is twice as large in amplitude. Multiply by 0.5 and it is half. This tool exposes that number directly as a Volume multiplier, running from 0.1x to 3x in steps of 0.1, and applies it with ffmpeg's volume filter.
It is a plain gain change, not a smart one. It does not analyze loudness, even out quiet and loud passages, or protect against distortion. Every moment of the recording is scaled by the same amount.
When a boost or reduction helps
The typical case is a recording that is simply too quiet: a voice memo taken from across a room, a lecture, or a clip from a phone with a weak microphone. Raising the multiplier makes the whole file louder so it is easier to hear without turning your speakers up.
Reducing is just as valid. A clip that is too loud next to the others in a project can be brought down with a multiplier below 1. Be careful with large boosts, though. If the original already reaches near its peak level, multiplying it can push the signal past the maximum the format can hold, and the loud parts will clip, which sounds harsh and cannot be undone. Background noise also gets louder when you boost, so a hissy recording may sound worse. Consider the Noise Reducer first.
How to change the volume with this tool
- Drag an audio file onto the drop area, or click it to browse.
- The file name and size appear along with a slider labelled Volume multiplier. It starts at 1.5x. Drag it between 0.1x and 3.0x.
- Click Run. On first use the page downloads the ffmpeg engine (roughly 30MB), shown with a progress bar.
- Listen to the result in the audio player. If it is not right, change the slider and click Run again.
- Click Download. The output is an MP3 named after your original file with "-volume" added, for example
lecture-volume.mp3. - Start over clears the file.
Processing happens in your browser and nothing is uploaded.
Choosing a sensible multiplier
Start small. A multiplier of 1.5x makes the signal half again as large, and 2x doubles it. Many quiet recordings improve with something in that range, while 3x is a very large jump that is likely to distort anything that was not truly faint.
Always listen to the loudest part of the result, not just the beginning. Distortion shows up at the peaks. If you hear crackling, lower the multiplier and run again from the original file rather than boosting the already boosted copy.
The output is always MP3, whatever your input format, so the file is re-encoded and loses a small amount of quality. Keep your original. For a clip that is too long, trim it first with the Audio Cutter.