AudioToText
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Reduce the size of an audio file

Most voice recordings can be reduced to a tenth of their size with no perceptible loss. Upload yours and check the result.

  1. 1File
  2. 2Settings
  3. 3Processing
  4. 4Download
  • MP3
  • WAV
  • M4A
  • AAC
  • OGG
  • FLAC
  • OPUS

About this tool

Twenty minutes of conversation can take up sixty megabytes if recorded with a recorder's or phone's factory settings: two channels, a bitrate meant for music, and frequencies the human voice never reaches. Adjusting those two parameters to what voice actually needs reduces those same twenty minutes to three or four megabytes with no audible loss.

The two factors that matter most are bitrate and channel count. Converting a stereo recording to mono halves the file size, since both channels usually contain the same duplicated voice.

Features

  • One-click mono conversion, the most effective reduction for voice recordings.
  • Before-and-after size comparison shown on screen.
  • Supports uncompressed WAV files, where the reduction is most noticeable.
  • The file isn't uploaded to any server: it's processed in your browser.

How it works

  1. 1

    Upload the audio

    MP3, WAV, M4A, FLAC, OGG and other common formats.

  2. 2

    Choose the compression level

    96 kbps is enough for speech. With music, use 128 kbps. Mono halves the size further.

  3. 3

    Download the result

    The original size, the final size and the percentage saved are shown.

In detail

Bitrate, and why a voice needs very little of it

Bitrate is the amount of data stored for every second of audio. The human voice sits between 80 and 3,500 Hz, well below the 20 Hz to 20,000 Hz range a CD must cover; that's why a CD uses 1,411 kbps, while a voice recording works perfectly with a fraction of that figure.

A voice recording at 96 kbps is indistinguishable from one at 320 kbps to the human ear, while taking up a third of the space. Below that, the difference becomes noticeable: at 48 kbps the voice takes on a metallic quality, though it remains intelligible. With background music, the recommended floor rises to 128 kbps.

Recording in stereo stores the same voice twice

Recorders default to stereo, a setting designed for music. Applied to an interview, meeting or lecture, this means storing the same sound twice over, since both channels contain nearly identical audio.

Converting to mono is the most effective reduction available for a voice recording, and one most compressors don't offer directly. It's applied with a single option, works on any existing recording, and doesn't affect what's heard, since there was no real difference between the two channels.

Frequently asked questions

Need to transcribe a video?

Upload it and get the text with timestamps, each voice identified and a summary. No account needed to start.

Transcribe my recordingSee pricing

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