How to make an audio file louder
- Choose an audio file. The input peak shows how much room it has before it reaches full scale.
- Drag the Gain slider, or press Normalize peak to −1 dBFS to raise the loudest peak as far as it can go without limiting.
- Keep the limiter on if you boost past that point. The Clipping meter shows how many samples it is catching.
- Press Play and switch between A (original) and B (adjusted) to compare.
- Choose MP3 or WAV and press Download.
Decibels and how loud it sounds
Gain is measured in decibels because hearing responds to ratios, not to fixed steps. Every +6 dB doubles the amplitude of the waveform, but a sound has to rise by roughly 10 dB before most people hear it as twice as loud. A change of 1 to 3 dB is subtle.
| Gain | Amplitude | How it tends to sound |
|---|---|---|
| +3 dB | × 1.41 | Just noticeably louder |
| +6 dB | × 2 | Clearly louder |
| +10 dB | × 3.16 | About twice as loud |
| +20 dB | × 10 | About four times as loud |
| −6 dB | × 0.5 | Clearly quieter |
These are rules of thumb for the middle of the frequency range, where hearing is most sensitive. Perceived loudness also depends on pitch and on how loud the sound already is, so treat the last column as a rough guide and trust the A/B preview.
What clipping is, and what the limiter does
Digital audio has a hard ceiling called 0 dBFS (decibels relative to full scale). A sample can't go above it, so when a boost pushes a peak past the ceiling, the top of the wave is cut flat. Flattened peaks sound like crackle or harsh distortion, and they can't be repaired afterwards.
The Clipping meter counts the samples that would go past 0 dBFS at the gain you've set. Even a fraction of a percent can be audible on drums or on hard consonants like "p" and "t". With the limiter on, the tool looks 5 milliseconds ahead, turns the gain down smoothly just before each loud peak and lets it recover over about 80 milliseconds, so the output never goes above −1 dBFS. Push the gain far enough and the limiter works almost constantly, which flattens the difference between loud and quiet parts. If the result starts to sound squashed or seems to pump, back the gain off.
The ceiling sits at −1 dBFS rather than 0 because MP3 and AAC encoding can raise peaks slightly. Apple's audio requirements for podcasts, for example, ask for true peaks no higher than −1 dBFS.
Peak normalization and loudness
Normalize peak to −1 dBFS sets the gain so the single loudest sample lands at −1 dBFS. It's the biggest boost possible without clipping or limiting. It doesn't make different files equally loud, though: a podcast with one loud laugh and a heavily compressed pop song can share the same peak and still sound far apart. Loudness standards measure average loudness instead, in LUFS (also written LKFS); Apple Podcasts, for instance, targets about −16 LKFS.
If normalizing barely changes a file, a few sharp peaks are holding it back. Raise the gain past the normalize point with the limiter on: the limiter turns those peaks down so the rest of the recording can come up.
Frequently asked questions
- Will boosting the volume lower the quality?
- Gain on its own doesn't add distortion as long as nothing clips, but it raises everything, including any hiss already in the recording. Quality loss comes from clipping, which the limiter prevents, and from saving to MP3 again, which is lossy. Choose WAV if you plan to edit the file further.
- Why is the maximum +20 dB?
- +20 dB multiplies the amplitude by ten, which is enough for almost any recording that has audible content. Beyond that, background noise rises with the voice or music. If Normalize would need more than +20 dB, the tool stops at +20 dB and tells you.
- The file is louder, but it still sounds quiet on my phone. Why?
- Peak level and perceived loudness aren't the same. If a few sharp peaks reach full scale, normalizing can't raise the rest much. Turn the gain up past the normalize point with the limiter on. Small phone speakers also reproduce little bass, so bass-heavy music sounds quieter on them.
- Does this change my original file?
- No. The tool reads the file, processes a copy in memory and downloads a new file. The original stays exactly as it was.
- Is my audio uploaded?
- No. Decoding, the limiter and MP3 or WAV encoding all run in your browser. Your files never leave your device.
Sources
- HyperPhysics, Georgia State University: Loudness (the 10 dB rule of thumb)
- sengpielaudio: Level change, amplitude and perceived loudness calculator
- Apple Podcasts for Creators: Audio requirements (−16 LKFS target, −1 dBFS true peak)
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