A lecture recorded from the back of the room, a voice memo held too far from the phone, or a song file that is noticeably quieter than the rest of a playlist: sometimes a file is simply too quiet, and maxing out the volume on every device you play it on is not a real solution.
This booster changes the level of the audio itself. Choose an amount in decibels or as a percentage, keep Prevent clipping switched on so the loudest moments do not distort, pick an output format, and press Convert. It also works the other way round: negative decibels or percentages below 100 make a file quieter. Files never leave your device.
Decibels, percentages and clipping
Gain can be described two ways. Decibels are the unit audio engineers use: +6 dB roughly doubles the amplitude of the signal, and around +10 dB is what most listeners perceive as twice as loud. Percent describes the amplitude directly, so 200 percent is the same as +6 dB, 150 percent is about +3.5 dB and 50 percent is about -6 dB. The booster accepts -30 to +30 dB, or 1 to 1000 percent, which is the same as -40 to +20 dB.
Digital audio has a hard ceiling, full scale. When boosting pushes a peak above it, the top of the waveform is cut off flat, which is heard as crackling or harsh distortion. That is why Prevent clipping is on by default: after the gain, a limiter holds every peak just under full scale, about -0.3 dBFS, while leaving everything below it untouched. For moderate boosts it is inaudible; for very large ones it flattens the loudest moments, which can make speech sound denser and music less punchy.
When a fixed boost is what you need
Quiet voice recordings
Phone memos and lecture recordings often peak far below full scale. A boost of 6 to 12 dB with the limiter on makes them comfortable to listen to on earbuds or in a car.
Matching one track to others by ear
When you know a file is a few decibels too quiet next to the rest, a fixed gain lets you correct exactly that amount.
Turning a file down
Sound effects, alert tones and music beds are sometimes far too loud. A negative gain such as -10 dB, or 30 percent, tames them without any other change.
Settings and output
Change by switches between Decibels and Percent. Gain (dB) starts at +6 and Volume (%) at 150. The same gain is applied to every file in the batch, so a quiet file and a loud file stay as different as they were; if you want them to end up equally loud, Normalize Audio measures each file and sets it to a loudness target instead.
Output format keeps the input's format by default, or saves as MP3, WAV, M4A or FLAC. WebM recordings, which the tool reads but does not write, become MP3 when Same as input is chosen. Compressed formats are encoded at 192 kbps, while WAV (16-bit) and FLAC are lossless. The audio converter that does the work runs in your browser and is downloaded once, about 31 MB. The result's name ends in -louder.
Как пользоваться инструментом
- Drop one or more MP3, WAV, OGG, M4A, AAC, FLAC or WebM files on the box above, or click it to browse.
- Under Change by, choose Decibels or Percent and type the Gain (dB) or Volume (%).
- Leave Prevent clipping on unless you specifically want the raw gain, and pick an Output format.
- Press Convert and download the louder (or quieter) files, singly or with Download all (.zip).
Limitations
- Boosting raises background noise and hiss by the same amount as the voice. Reduce noise first with Noise Reduction.
- A file that already peaks near full scale cannot get much louder without the limiter flattening it; in that case large boosts sound compressed rather than louder.
- With Prevent clipping switched off, boosts that push peaks past full scale distort.
- Only audio files are accepted. To make a video's sound louder, extract it with MP4 to MP3, boost it and put it back with Add Audio to Video.