Change audio speed without the chipmunk effect
This audio speed changer makes any recording faster or slower — anywhere from a quarter of normal speed to four times as fast — and saves the result as a new file. Drop in a podcast, an audiobook chapter, a lecture, a song you are learning or a voice message, pick a speed, listen to an eight-second preview and download it as MP3, M4A, WAV, FLAC or OGG.
By default the pitch stays exactly where it was, so a voice at 1.5× still sounds like the same person, only quicker, and a melody slowed to 0.75× stays in its original key. If you want the old tape-machine effect instead — higher and brighter when faster, deeper when slower, as in “nightcore” and “slowed” edits — switch the pitch setting to follow the speed.
Everything happens on your own device. The file is decoded by your browser, stretched by code running in the page and encoded locally, so private recordings never touch a server and there is no length or file-count limit beyond your device’s memory.
How to use the Audio Speed Changer
- Drop an audio file onto the box or click to choose one. Its duration, sample rate, channels, loudness and peak level appear, with the original in the Before player.
- Pick a speed from the buttons, drag the slider, type an exact value such as 1.35 in Exact speed, or choose one of the Presets. The note shows the new length straight away.
- Choose how the Pitch behaves: keep it for voices (WSOLA) or for music (phase vocoder), or let it follow the speed.
- Press Preview to hear eight seconds from the marker; tap the waveform to move the marker. The preview updates as you change the settings.
- Pick the format and quality under Save as, press Change speed, compare the result in the After player and press Download.
Audio Speed Changer features
0.25× to 4× in 0.01 steps
Six one-tap speeds, a logarithmic slider and an exact-value field, plus presets for podcasts, audiobooks, lectures, language learning, music practice, nightcore and slowed edits.
Two pitch-keeping engines
WSOLA (waveform-similarity overlap-add) keeps speech crisp; a phase vocoder with phase locking handles chords and full mixes more smoothly.
Tape mode
Let the pitch rise and fall with the speed, using a band-limited resampler so fast versions do not alias or crackle.
Live preview
Hear eight seconds of the result before processing the whole file, and A/B it against the original at the same spot.
Five export formats
MP3 (128–320 kbps), M4A/AAC, WAV (16-bit, 24-bit or 32-bit float), FLAC and OGG Vorbis; the format of the file you open is suggested first.
Private and free
No upload, no sign-up, no watermark. A progress bar shows each stage and Cancel stops at any time.
How long will it be? Speed and duration
The new length is the original length divided by the speed. A 60-minute podcast at 1.5× takes 40 minutes; a 3-minute song at 0.75× lasts 4 minutes. The table shows common choices for an hour of audio.
| Speed | Typical use | 60 minutes becomes |
|---|---|---|
| 0.5× | Transcribing a fast solo, learning lyrics | 2 h 0 min |
| 0.75× | Language learning, practising along | 1 h 20 min |
| 1.25× | Audiobooks, interviews | 48 min |
| 1.5× | Podcasts, recorded meetings | 40 min |
| 2× | Skimming lectures you know well | 30 min |
| 3× | Finding a spot in a long recording | 20 min |
Keep the pitch or let it follow?
- Keep pitch — voice (WSOLA). The sound is cut into 40 ms overlapping slices; each slice is shifted by up to 12 ms to where its waveform lines up best with the previous one, then the slices are added back together at the new spacing. Voices stay natural and consonants stay sharp. It is the best choice for podcasts, lectures and audiobooks.
- Keep pitch — music (phase vocoder). The audio is split into overlapping 2,048-sample spectra and every frequency’s phase is advanced to the new timing, with each harmonic’s neighbouring bins locked to it (identity phase locking). Sustained chords and full mixes sound smoother, but sharp drum hits can soften slightly.
- Pitch follows speed (tape). No stretching at all — the samples are simply played faster or slower, so 2× is exactly one octave higher and 0.5× one octave lower. Use it for nightcore, slowed-and-reverb edits or to correct a recording made at the wrong speed.
Getting clean results
Time-stretching always has to invent or remove a little of the sound, so quality is best near normal speed: between about 0.6× and 2× speech sounds natural, while extreme settings can add a slight echo. A gentle safety limiter keeps the result from clipping.
To speed up only part of a recording, trim it first with the Audio Cutter. If you need a song in a different key rather than at a different tempo, use the Audio Pitch Changer; to find the tempo you are aiming for, the BPM Detector measures it. For videos, the Video Speed Changer retimes picture and sound together.
Audio Speed Changer FAQ
How do I slow down a song without changing the pitch?
Open the song, choose a speed below 1× such as 0.75×, leave Pitch on one of the “Keep pitch” options (the phase vocoder suits music) and press Change speed. The tempo drops while every note stays in the same key.
Is this audio speed changer free and private?
Yes. There is no sign-up, limit or watermark, and the audio is processed entirely inside your browser — the file is never uploaded to a server.
Which formats can I open and save?
Anything your browser can decode: MP3, WAV, M4A/AAC, Ogg Vorbis, Opus, FLAC and WebM audio. You can save as MP3, M4A, WAV, FLAC or OGG Vorbis, with the format of your original suggested first.
What is the difference between WSOLA and the phase vocoder?
WSOLA rearranges short slices of the waveform and works best on single voices. The phase vocoder works on the frequency spectrum and handles chords and full mixes more smoothly. Try both with the preview — the better one depends on the material.
Why does audio sound echoey at very high or low speeds?
At extreme speeds a time-stretch has to repeat or skip a lot of tiny slices, which the ear can hear as a slight echo or flutter. Staying between about 0.6× and 2× gives the most natural sound.
Can I make a nightcore or slowed version?
Yes. Choose the Nightcore (1.25×) or Slowed (0.85×) preset, or set any speed with Pitch on “Pitch follows speed”. For the slowed-and-reverb style, add reverb afterwards with the Voice Changer’s Reverb effect.