RaahUPSC · Audio Tools
Change Audio Speed
Play a lecture faster or slow a language lesson down without changing the pitch of the voice. A slider sets any speed from 0.5× to 2× in steps of 0.05.
✓ No upload · ✓ No sign-up · ✓ No watermark
How to use Change Audio Speed
- Add one or more audio files: MP3, WAV, M4A, AAC, OGG, FLAC, Opus or WMA.
- Move the Speed × slider; it starts at 1.5× and goes from 0.5× (half speed) to 2× (double).
- Click Convert and wait while each file is processed.
- Download the results, named with -speed and kept in their original format.
Tempo change without pitch shift
The tool applies FFmpeg's atempo filter, a time-stretching algorithm that changes duration while keeping pitch, so voices do not turn squeaky or deep. A one-hour recording at 1.5× becomes 40 minutes; at 0.75× it becomes 80. Output is re-encoded in the input's format, so WAV and FLAC stay lossless.
Aspirants revising recorded classes or newspaper analysis can often follow speech comfortably at 1.25× to 1.5×. Slowing to 0.75× helps with dictation practice, transcription and learning pronunciation in a new language.
Limitations
- The range is limited to 0.5×–2×; for more extreme changes, run the result through again.
- Strong time-stretching can add slight echo or warble, especially on music.
- The same speed is applied to every file in the batch.
Frequently asked questions
Will the voice sound higher when sped up?
No. atempo preserves pitch; only the pace changes.
What format is the output?
The same as the input. MP3 stays MP3 (re-encoded at VBR quality 2), M4A stays M4A at 192 kbps AAC, and WAV stays WAV.
How long will processing take?
Roughly proportional to the file's length and your device's speed. Desktop browsers are much faster than phones for long lectures.
Are my lectures uploaded anywhere?
They are processed locally by FFmpeg WebAssembly and never sent to a server.