What is an AMR file?
AMR (Adaptive Multi-Rate) is an audio compression format optimized specifically for speech coding on mobile networks. Developed by the European Telecommunications Standards Institute (ETSI) and standardized by 3GPP, AMR became the mandatory speech codec for GSM networks and is widely used in 3G (UMTS) networks. The format earned its “Adaptive Multi-Rate” name because it dynamically switches between eight different bitrates (4.75 to 12.2 kbps for AMR-NB) based on network conditions and available bandwidth.
AMR prioritizes small file sizes and intelligibility of human speech — qualities that make it ideal for voice calls and recordings on older mobile hardware, but unsuitable for music where audio fidelity matters.
How to open AMR files
- VLC Media Player (Windows, macOS, Linux) — Free, plays AMR natively
- QuickTime Player (macOS) — Built-in support on Mac
- AMR Player (Windows) — Lightweight free player dedicated to AMR
- FFmpeg — Command-line tool for playback and conversion
- Android — Native support in the built-in voice recorder and media player
Technical specifications
| Property | Value |
|---|---|
| Variants | AMR-NB (Narrowband, 8 kHz), AMR-WB (Wideband, 16 kHz) |
| Sample rate | 8,000 Hz (NB) / 16,000 Hz (WB) |
| Bitrates | AMR-NB: 4.75–12.2 kbps; AMR-WB: 6.6–23.85 kbps |
| Channels | Mono only |
| Frame size | 20 ms per frame |
| Standard | 3GPP TS 26.071 (NB), TS 26.171 (WB) |
| Magic bytes | 23 21 41 4D 52 (#!AMR in ASCII) |
AMR-NB vs AMR-WB
| Variant | Sample rate | Quality | Use |
|---|---|---|---|
| AMR-NB (Narrowband) | 8 kHz | Phone-quality speech | 2G/3G calls, basic voice memos |
| AMR-WB (Wideband) | 16 kHz | HD Voice quality | VoLTE, modern VoIP, better intelligibility |
AMR-WB (also called G.722.2) is significantly better quality — voices sound more natural and are easier to understand at the same bitrate. It is the codec behind “HD Voice” calls on modern carriers.
Common use cases
- Mobile voice recordings: Android’s built-in voice recorder often saves in AMR format by default on older devices
- MMS messages: Audio clips sent in multimedia messages use AMR for compact file size
- VoIP and cellular calls: The AMR codec runs in real-time on baseband processors during actual phone calls
- Voicemail storage: Mobile carriers and voicemail systems store messages as AMR files
Converting AMR to MP3 or WAV
AMR files are not widely supported outside mobile devices. Convert to MP3 or WAV for compatibility with all players:
Using FFmpeg:
# AMR to MP3
ffmpeg -i recording.amr recording.mp3
# AMR to WAV
ffmpeg -i recording.amr recording.wav
# AMR-WB (higher quality) to MP3 at 128kbps
ffmpeg -i recording.amr -b:a 128k output.mp3Online tools: CloudConvert, Zamzar, and similar services convert AMR files in the browser without software installation.
Audio quality limitations
AMR was optimized for speech, not music. The 8 kHz sample rate of AMR-NB limits audio to frequencies below 4 kHz — music sounds “tinny” and lacks bass. If you receive an AMR file containing music, converting it to MP3 will not recover lost quality; the high-frequency information was never captured. AMR recordings are perfectly clear for speech but will never approach music quality regardless of conversion format.