Volume Booster

How to make an audio file louder

Three steps, in your browser.

1. 1

   Drop the recording

   MP3, M4A from an iPhone, WAV, FLAC and other common formats. The page reads it and shows how loud it is now: the highest peak and the average level.

2. 2

   Normalize, or boost by dB

   Normalize lifts the whole file until its loudest moment sits at -1 dB. If that is not enough, switch to Boost and add up to 20 dB; the limiter holds the peaks.

3. 3

   Listen, then download

   Play the original and the louder version side by side, check the before and after numbers, and save the result as an MP3 or a 16-bit WAV.

Normalize or boost: which one to use

• Normalize first

  One fixed gain for the whole file, chosen so the loudest moment lands at -1 dB. The balance between quiet and loud parts stays exactly as it was recorded.

• Boost when one sound holds it back

  If a cough, a cup set down on the table or a door is the loudest peak, normalize can only add a little. Boost goes further and lets the limiter flatten those few peaks.

• Why -1 dB and not 0

  A peak sitting right at 0 dB can clip once an MP3 encoder or a player touches it. One decibel of headroom avoids that; the broadcast loudness standard EBU R 128 uses the same -1 dB ceiling.

• Reading the limiter report

  After a boost the page says how many samples would have clipped and how far the limiter turned them down. A few dB on a few peaks is hard to hear; if it warns of heavy limiting, boost less.

Recordings that come out too quiet

• A meeting recorded on a phone lying on the table

  The people at the far end sit several times further from the microphone than the person next to it. Normalize first; if the far voices are still faint, boost 6 to 10 dB and listen to the near voice for squashing.

• An interview with the recorder too far away

  Level drops quickly with distance. Boost the file so you can work with it, and next time put the phone or recorder within arm's reach of the person speaking.

• A voice memo you need to send

  Quiet memos are hard to hear on a phone speaker in a car or a warehouse. Normalize, save as MP3 at 128 kbps and send that copy.

• An online meeting saved as audio

  A recording of a video call can come out quiet when every voice was set low. Normalize brings the whole file up without changing who sounds louder than whom.

What making it louder cannot fix

How much louder is +6 dB?

Gain in decibels multiplies the height of the waveform by 10 to the power of dB/20.