Volume Booster and Normalizer

How to boost or normalize an audio file

1. Drop an audio file on the drop zone or click it to choose one. The tool decodes it and shows its Original levels: Peak, RMS and Loudness (approx.).
2. Choose a Method: - Boost by a set amount: move the Gain (dB) slider, from −12 to +30 dB. - Normalize peak: the loudest sample is brought to the Target peak (dBFS), −1 dBFS by default. - Normalize loudness (approx. LUFS): the average loudness is brought to the Target loudness (≈ LUFS), −14 by default.
3. Keep the Limiter (prevents clipping) on unless you want the raw gain. Its Limiter ceiling (dBFS) is −1 by default.
4. Check the predicted Applied gain, Output peak and Output loudness (approx.). A red warning appears if the result would clip.
5. Press Preview to listen, then choose the Format and press Export. Play the result and press Download.

Decibels in a nutshell

Digital audio is measured in dBFS, decibels relative to full scale: 0 dBFS is the largest value a file can store, and everything else is negative. Every +6 dB doubles the amplitude; +10 dB sounds roughly twice as loud. A gain of +6 dB on a file that peaks at −3 dBFS would push the peak to +3 dBFS, which can’t be stored: the tops of the waveform get cut off. That is clipping, heard as harsh distortion.

The Peak is the highest sample. The RMS (root mean square) is the average power of the whole file, which is closer to how loud it sounds. A spoken podcast might peak at −1 dBFS with an RMS around −20 dBFS: the gap between the two is the dynamic range.

The limiter

To make quiet audio louder than its peaks allow, this tool uses a look-ahead limiter. It sees each peak 5 ms before it arrives, turns the gain down smoothly just enough to keep it under the ceiling, then recovers over about 100 ms. Short peaks (consonants, drum hits) are tamed while the rest gets the full boost. Pushing 10 dB or more of limiting makes music sound flat and “squashed”, so listen to the preview. The −1 dBFS ceiling leaves headroom for MP3 encoding, which can create small overshoots.

Loudness normalization (approximation)

Streaming services and broadcasters normalize to a loudness in LUFS measured with the ITU-R BS.1770 method: about −14 LUFS for Spotify and YouTube, −16 for many podcasts, −23 for European TV (EBU R128). This tool measures an approximation: it applies the BS.1770 gating (400 ms blocks, silence and quiet passages ignored) to the plain signal power, but without the K-weighting filter that reduces bass and boosts treble. For voice and most music, the value is within a dB or two of a real LUFS meter; bass-heavy content reads a little high. Use a dedicated meter when a delivery spec requires an exact figure.