Audio Speed Changer

How to change the speed of an audio file

Three steps, in your browser.

1. 1

   Drop the recording

   MP3, M4A from an iPhone, WAV, FLAC and other common formats up to 100 MB and 60 minutes. The page reads it and shows how long it runs now.

2. 2

   Pick a speed and listen

   Drag the slider or tap a preset, 0.75× to 2×, or type a value up to 3×. The pitch is kept by default, so voices sound natural. Press play on the preview to hear the original at that speed before anything is written.

3. 3

   Process and download

   The whole file is rendered at the new speed with a progress bar, then saved as an MP3 at the bitrate you choose or as a 16-bit WAV. The new length is shown next to the file name.

Pitch kept or pitch changed

• Keep the pitch for speech

  The default. The page stretches time without moving the pitch, so a voice at 1.5× is the same voice, just quicker. This is what you want for interviews, calls, lectures and podcasts.

• Let the pitch move for effects

  The second option resamples the audio the way a tape deck at the wrong speed would: faster is higher, slower is deeper. Useful for sound effects or music experiments, not for understanding speech.

• How the pitch is kept

  The recording is cut into short overlapping slices, each about 40 milliseconds long. To go faster, slices are dropped; to go slower, slices are repeated. Each cut lands where the waveform lines up with the previous slice, so the join does not click.

• What it costs in quality

  Up to about 2× speech stays clear. Beyond that, consonants start to blur into each other and music can sound smeared, which is a limit of the method, not of this page. Slowing down below 0.75× adds a slight echo-like texture on sustained sounds.

When a different speed helps

• Listening back to an interview

  An hour of recording is forty minutes at 1.5×. Pitch kept, the speakers still sound like themselves, and you can slow down again for the quotes you want exactly.

• Slowing a fast talker for transcription

  At 0.75× a rushed answer becomes easy to type along with. Keep the pitch so the words stay clear; letting the pitch drop makes them harder to catch, not easier.

• Reviewing a sales call

  Jump through the small talk at 2×, then drop to 1× for the objection and the close. The saved file keeps its timestamps in proportion, so a note at minute 30 is at minute 15 in the 2× copy.

• A podcast episode on the commute

  Save an episode at 1.25× or 1.5× as MP3 and play it in any app, including ones without their own speed control.

How long a 60-minute recording runs

The new length is the old length divided by the speed.

What changing the speed does not change