AMR files: a codec built for phone calls, and what that means
Why AMR recordings sound like phone calls, why no bitrate can fix that, and how to make them playable. Convert AMR in your browser, no upload.
At a glance
- Type
- Audio
- Compression
- Lossy
- Extensions
- .amr
- MIME type
- audio/amr
- Common codecs
- amr_nb
- Also known as
- Adaptive Multi-Rate
AMR — Adaptive Multi-Rate — is a speech codec rather than an audio codec. It was standardised for GSM mobile networks and models the human vocal tract specifically, sampling at 8 kHz and reproducing roughly the frequency range of a telephone call. That is why an AMR file is astonishingly small, and why music through it sounds destroyed rather than merely compressed.
Read more
The files you will find in this format are voice memos from feature phones and early smartphones, voicemail exports, and call recordings. Almost nothing outside a phone decodes AMR, so converting to MP3 is usually the only way to keep such a recording playable — and it is worth doing while tools still read the format at all.
What conversion cannot do is improve it. Everything above about 4 kHz was never captured, so the MP3 will sound exactly as narrow as the original. For that reason keep the bitrate low: 64 or 96 kbps is entirely sufficient for 8 kHz mono speech, and anything higher just stores silence in frequency bands the source never used.
Convert AMR to other formats
FAQ
Why does my AMR recording sound so muffled?
Because AMR captures roughly the range of a telephone call — 8 kHz sampling, tuned for speech. Everything above about 4 kHz was never recorded.
Can converting improve the quality?
No. The missing frequencies are not stored anywhere. Conversion changes the format so more things can play it; it cannot invent detail.
What bitrate should I use?
64 or 96 kbps. The source is 8 kHz mono speech, so a higher bitrate produces a much larger file with no audible gain at all.
Where do AMR files come from?
Voice memos on feature phones and early smartphones, voicemail exports, and call recording apps. It was the standard speech format on mobile networks.
Should I convert my old recordings now?
If you care about them, yes. Software support for AMR is quietly disappearing, and converting while tools still read it is easier than trying later.
Is anything uploaded?
No. Voice memos and call recordings are about as personal as audio gets, and they stay on your machine.