2Choose a multiplier — 0.5x for half speed, 2x for double — staying roughly inside 0.75x to 2x if the content is speech.
3Run it; the time-stretch preserves pitch, so voices stay natural instead of transposing upward.
4Download the retimed Audio file — shorter or longer in exact proportion, with the bitrate and sample rate untouched.
Change Audio Speed FAQ
How does Change Audio Speed change the playback rate?
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Concretely, pitch-preserving time-stretch is applied to whatever you uploaded, with the encode path chosen from the source codec. Choose a multiplier — 0.5x for half speed, 2x for double — and the whole file is retimed.
Will speeding it up make voices sound high-pitched?
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No. The time-stretch preserves pitch, so a 1.5x speech track sounds like the same person talking faster rather than like a chipmunk. That is the difference between a proper time-stretch and simply playing the samples faster.
Does the source format affect the result?
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It does. this format is read and written by the same streaming pipeline as everything else we support. That determines whether the retimed result can be written back cheaply or has to be fully re-encoded.
Anything specific to Audio here?
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Yes — the codec is detected from the stream, so a mislabelled extension does not derail the job. Worth knowing before you commit to a large speed change.
How far can I push the speed before it sounds wrong?
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Roughly 0.75x to 2x is transparent for speech. Beyond about 2.5x the stretch artefacts become audible on any algorithm, and below 0.5x the reconstruction has to invent too much. Music tolerates far less than speech does.
Does the file get shorter, and does it get smaller?
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Shorter, yes, and in exact proportion — an hour of audio at 1.5x is forty minutes. The file shrinks by roughly the same proportion because there is less material to encode. The bitrate, the sample rate and the channel layout are all left exactly as they were.
Which audio formats does Change Audio Speed accept?
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MP3, WAV, AAC, M4A, FLAC, OGG, Opus, WMA and AIFF. Codecs are detected from the stream rather than the extension, so a mislabelled file still works and a mixed batch is handled per file.
Is there a file size limit on Change Audio Speed?
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Yes: free accounts process audio up to 200 MB per file whichever codec you brought; ffmpeg handles the decode and encode. In practice that limit only bites on uncompressed WAV; a compressed file of the same length is nowhere near it.
Will Change Audio Speed lower the quality of my audio files?
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It depends on the source. Lossless input (WAV, FLAC, AIFF) is edited sample-exactly and loses nothing. Lossy input has already discarded detail once, so where the job can be done by copying the encoded stream rather than re-encoding it, that is the path taken.
Can I run Change Audio Speed on several audio files at once?
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Yes. The set queues in parallel with identical settings, which is how you process an album or a podcast back catalogue without repeating yourself.
Do tags and cover art survive?
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Yes — ID3, Vorbis comments and MP4 atoms are carried across along with embedded artwork, so processed files still sort correctly in a music library.
Does Change Audio Speed cost anything?
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No. Change Audio Speed is free with no account, and nothing is added to the audio. Uploads are deleted from the workers shortly after the job completes.
