Speed up audio, keep the voice
Drop a recording on the box, choose a speed from 1.0× to 3.0×, hear it in the preview and save the sped-up file as a WAV. The recording is read on your own device and never leaves your browser: no upload, no account, no server that touches your audio.
The recording
Runs entirely on your deviceDrop the recording here
or — mp3, wav, m4a, mp4 and what your browser can decode, up to 64 MB
recording.mp3
0:00 / —
Checking whether this browser can keep the pitch in the preview…
The recording never leaves your browser: it is read with the File API, decoded with the Web Audio API and written into a WAV file by JavaScript on your own device. The page loads no third-party code, has no form and no account, and your file is never sent to our server. The only request the page makes besides the page itself is for the demo recording of the button “Try it on a sample recording”.
How to speed up a recording
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Open the file
Drop the recording on the box or choose it from your device. The file is read there, on your own computer, and is never uploaded.
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Choose the speed
Move the slider from 1.0× to 3.0× in steps of 0.05, or press one of the presets: 1.25×, 1.5×, 1.75×, 2×, 2.5× or 3×.
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Listen
The preview plays the recording at the chosen speed. The block under it says whether your browser keeps the pitch in the preview or not.
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Download
Press “Download the sped-up WAV”. The file is written on your device as a 16-bit WAV with the pitch of the original voice.
What each speed does to the length
The length of the recording after the speedup is the length before it divided by the speed. Nothing is rounded away: at 2× the recording is exactly half as long.
| Speed | A 60-minute recording | A 10-minute recording | Time you get back |
|---|---|---|---|
| 1.25× | 48 min | 8 min | 20% of the length |
| 1.5× | 40 min | 6 min 40 sec | one third of the length |
| 1.75× | 34 min 17 sec | 5 min 43 sec | 43% of the length |
| 2× | 30 min | 5 min | half of the length |
| 2.5× | 24 min | 4 min | 60% of the length |
| 3× | 20 min | 3 min 20 sec | two thirds of the length |
The numbers in this table are the division of the length by the speed, rounded to the second. The tool on this page shows the numbers of your own file, computed the same way.
Why the voice does not turn into a chipmunk
The simplest way to make a recording faster is to read the samples closer to each other. The voice then keeps its shape but rises in pitch — the well-known chipmunk. This tool does not do that.
- The recording is cut into pieces. Every piece covers about 20 milliseconds of the original, and the pieces are laid over each other in the output.
- Every piece is looked for in the recording. For each piece the tool searches for the place where the sound continues most like the piece before it, and takes the piece from there. The waveform inside a piece stays the waveform it was.
- The pieces are joined with a smooth window. The overlaps are summed and divided by the sum of the window, so the level of the recording stays where it was.
- The result is a shorter recording with the same pitch. At 2× the recording lasts exactly half as long and the voice sounds like the same voice.
- The preview is a separate thing. The preview is played by the browser itself, which has its own way of keeping the pitch. If your browser cannot do it, the page says so in plain words, and the downloaded file keeps the pitch anyway.
Questions this page answers
Does the recording go to your server?
No. The file is read in your browser with the File API, decoded with the Web Audio API and written into a WAV file by JavaScript on your own device. The recording never leaves your browser: the page loads no third-party code, there is no form and no account, and nothing is written to a log. The server only sends the page itself, the same way it does for every visitor.
Which files can I speed up?
Whatever your browser can decode: mp3, wav, m4a, aac, ogg, opus, flac, webm and the usual video containers such as mp4 and mov. The tool reads the file with the Web Audio API, so the list of formats is the list of formats your browser supports — and the tool says so plainly when it cannot decode a file. One file may be up to 64 MB, the same limit as the service uses.
Will the voice sound like a chipmunk?
No. The tool stretches the recording instead of speeding it up: the pieces of the recording are laid over each other, so the pitch stays where it was and only the length changes. The preview is played by the browser itself, and the page tells you whether your browser keeps the pitch in the preview — if it does not, the preview will sound higher and the page says that too. The downloaded WAV keeps the pitch in every browser.
How do I save the result?
Press “Download the sped-up WAV”. The file is written on your own device as a 16-bit PCM WAV with the same sample rate as the recording you opened, and the name of your file with the speed added to it. The page shows the size of the file and its length after the download.
How much time do I save?
The new length is the old length divided by the speed, and the block under the slider shows both numbers for your own file: the original length, the length after the speedup and the time you get back. At 2× the recording is exactly half as long, at 3× exactly a third.
Is the recording safe to use on a private conversation?
Nothing is uploaded, so the file does not reach any server — but keep in mind that the tool runs in the same browser as everything else you have open, and that the export is written to your usual download folder. If the recording must not leave the device at all, close the page after the download.
Need the text, not only the sound?
A faster recording is still a recording. When you need the words themselves — a transcript with timecodes, speaker labels and exports to TXT, Markdown, SRT, VTT, CSV or DOCX — send the file to Transcrib Si.
The guide to the service: the formats, the limits, the exports and the prices.
The service in three steps, and what it costs.
The whole history, the API keys and the billing.
Related pages
How long a text takes to say out loud, in the browser.
Subtitle characters per second
Whether the subtitles of your video can be read.
The “ums” and the “ahs” of a transcript, counted and marked.
A subtitle file from one format into another.
The other way round, also in the browser.
What the transcription services charge for your hours.
Mark Burmistrov, Founder.
The tool on this page has no server behind it: the file is read, sped up and written into a WAV file on the device of the visitor. The author of the page and the publisher of the site are the same person. Questions and corrections: support@transcrib.si.