Convert AMR to MP3

What AMR is, and why nothing plays it

Adaptive Multi-Rate is the speech codec GSM networks used for voice calls. It encodes a narrowband signal — roughly 300 Hz to 3.4 kHz, the telephone band — at eight selectable rates between 4.75 and 12.2 kbps, switching between them as network conditions change. That is spectacularly efficient for speech and completely unsuitable for anything else.

Because it came out of the mobile-telephony world rather than the media world, desktop software largely ignored it. Windows and macOS will not open a bare .amr without extra codecs, most editors refuse it, and transcription services often reject it on upload. Yet Android call recorders, Samsung and Nokia voice memo apps, dashcams and a great many voicemail systems still produce it.

The three extensions you will encounter

• .amr — a bare AMR stream with a six-byte magic header. The classic case.
• .3ga — Samsung’s naming for AMR (or sometimes AAC) inside a 3GP container. Same audio, different wrapper.
• .3gp — the general 3GPP container, which may hold video as well. Only the audio track is converted here.
• .awb — AMR-Wideband, a later 16 kHz variant used for HD Voice. Noticeably clearer, and handled the same way.

Converting will not make it sound better

This is the single most important thing to understand, and no converter will tell you honestly because it makes their product sound worse. AMR discarded everything outside the telephone band at the moment of recording. Those frequencies were never written to the file. Re-encoding at 320 kbps produces a large MP3 containing exactly the same narrowband audio — you have changed the wrapper, not the content.

What conversion genuinely gives you is a file that opens everywhere, can be loaded into an editor, can be sent to a transcription service, and can be joined to other recordings. Those are good reasons. "Improving the quality" is not one, and anything advertising AMR enhancement is selling you a noise gate.

64–96 kbps mono is the right setting. It is comfortably more than the source contains, and keeps a one-hour call recording under 45 MB.

Getting the most out of a poor recording

If the recording is hard to make out, the useful moves are all downstream of the format:

• Force mono if it is not already — it is a single-channel source, and stereo just duplicates it at twice the size.
• Normalise the loudness using the option in the advanced panel. AMR recordings are often very quiet, and bringing them to −16 LUFS makes them far easier to listen to and to transcribe.
• Do the real cleanup in an editor. A high-pass filter at 200 Hz and gentle compression in Audacity will help more than any converter setting. Convert to WAV first if the editor prefers it.

Why these files in particular should never be uploaded

Look at what AMR files actually are. Call recordings. Voicemail. Dictated notes. Interviews. Evidence gathered for a dispute. Recordings people made because they expected to need them later. This is among the most sensitive audio anyone owns, and the standard advice — "just use an online converter" — means handing it to an unknown server governed by a policy you cannot audit.

Nothing is uploaded here. The AMR decoder is compiled into a WebAssembly build of FFmpeg served from this site, and it runs inside your browser tab; the site’s Content-Security-Policy permits no third-party origin, so there is no destination even in principle. Verify it in ten seconds: open the Network tab, or simply turn off Wi-Fi, and convert anyway.

If a file will not decode

Two things usually explain it. Either the file is truncated — call recorders are frequently killed mid-write when a call ends or a phone runs out of storage — or it is not AMR at all despite the extension, which happens when a file manager renames things during a transfer. A valid AMR file begins with the ASCII bytes #!AMR; a 3GP file has ftyp3gp near the start. Anything else needs the general audio converter, which sniffs the container itself.