Change Audio Speed
Speed up or slow down audio, optionally preserving pitch.
How to change audio speed
- Add an audio file.
- Pick a speed. 1.5× is a comfortable listening speed for most speech; 2× is fast but intelligible.
- Pitch preservation is on by default — disable it only if you want the pitch shift as an effect.
About this tool
Listening at 1.5× or 2× speed is a common way to get through long podcasts and lectures. The technique works because human speech recognition is remarkably robust to tempo changes — the brain can extract meaning at speeds well above normal speech rate as long as the pitch and formant structure are preserved. Without pitch preservation, doubled-speed speech sounds like a small creature rather than a fast human.
The practical upper limit for pitch-preserved time-stretching on speech is around 2.5×, where most listeners report needing to concentrate hard to follow. For music the limit is lower — the phase-vocoder trades off accuracy against artefacts and music has more complex spectral content for it to manage. At 2× with pitch preservation, drum transients in particular develop a smearing character that is not present in the original.