AMR Compressor
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Supports: AMR
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Need help?How to Compress AMR Audio Online
- Upload Your AMR Files — Drag and drop or select one or more AMR audio files.
- Choose a Codec Mode — Under Audio Codec, select AMR Narrow Band (AMR-NB, 8 kHz sample rate) or AMR Wide Band (AMR-WB, 16 kHz sample rate). AMR-NB is the default and produces smaller files; AMR-WB offers better speech clarity.
- Select a Constant Bitrate — AMR uses fixed bitrate tiers. For AMR-NB: 4.75, 5.15, 5.90, 6.70, 7.40 (Toll Quality), 7.95, 10.2, or 12.2 kbps. For AMR-WB: 6.60, 8.85, 12.65 (High Quality), 14.25, 15.85, 18.25, 19.85, 23.05, or 23.85 kbps.
- Trim (Optional) — Set a start time and duration in seconds or HH:MM:SS.sss to extract a specific segment.
- Compress & Download — Click Compress and download the smaller AMR file.
Why Compress AMR Files?
AMR (Adaptive Multi-Rate) is the standard speech codec used by GSM and 3G mobile networks worldwide. If you have voice recordings, voicemail exports, or call recordings in AMR format, they are already compact — but you can reduce them further by switching from AMR-WB to AMR-NB or by selecting a lower bitrate tier. This is useful when you need to fit recordings onto devices with very limited storage, send voice messages over slow network connections, or archive large volumes of call recordings.
AMR-NB vs AMR-WB Bitrate Tiers
| Codec | Bitrate | Quality | ~Size per Minute |
|---|---|---|---|
| AMR-NB | 4.75 kbps | Low (minimum) | ~35 KB |
| AMR-NB | 7.40 kbps | Toll quality | ~55 KB |
| AMR-NB | 12.2 kbps | Best NB quality | ~92 KB |
| AMR-WB | 6.60 kbps | Low wideband | ~50 KB |
| AMR-WB | 12.65 kbps | High quality WB | ~95 KB |
| AMR-WB | 23.85 kbps | Best WB quality | ~179 KB |
AMR vs Other Speech Codecs
| Feature | AMR-NB | AMR-WB | Opus | Speex |
|---|---|---|---|---|
| Sample rate | 8 kHz | 16 kHz | 8–48 kHz | 8–32 kHz |
| Bitrate range | 4.75–12.2 kbps | 6.60–23.85 kbps | 6–510 kbps | 2–44 kbps |
| Audio bandwidth | 300–3400 Hz | 50–7000 Hz | 20–20000 Hz | 300–8000 Hz |
| Primary use | GSM voice calls | 3G/VoLTE calls | VoIP, streaming | VoIP (legacy) |
| Mobile device support | Universal | Wide | App-dependent | Limited |
Use Cases
- Voicemail & call recordings — Reduce AMR-WB recordings to AMR-NB when wideband clarity is not needed, cutting file size by 50%+.
- Bulk archival — Compress thousands of call center recordings to the lowest acceptable bitrate (7.40 kbps AMR-NB for toll quality) to save storage.
- Slow network transfer — AMR at 4.75 kbps requires under 5 kilobits per second, making it viable for extremely low-bandwidth connections.
- WhatsApp / messaging exports — Voice messages from WhatsApp and other messaging apps often use AMR or Opus. Trim and re-compress to keep only the relevant portion.
What is the difference between AMR-NB and AMR-WB?
AMR-NB (Narrow Band) samples audio at 8 kHz and captures frequencies up to 3400 Hz — sufficient for basic telephone-quality speech. AMR-WB (Wide Band) samples at 16 kHz and captures up to 7000 Hz, producing noticeably clearer and more natural-sounding speech. AMR-WB files are roughly twice the size of AMR-NB at comparable quality tiers.
What is the best AMR bitrate for voice recordings?
For AMR-NB, 7.40 kbps (Toll Quality) offers the best balance between clarity and file size. For AMR-WB, 12.65 kbps (High Quality) is the recommended starting point. Go lower only if storage or bandwidth is severely constrained.
Why is AMR limited to mono audio?
AMR was designed exclusively for speech coding in mobile telephony, which is inherently mono. The codec's compression algorithms are optimized for a single voice channel. For stereo audio, convert to a different format like AAC or Opus.
Can I trim an AMR file while compressing?
Yes. Use the Trim option to set a start time and duration in seconds or HH:MM:SS.sss. Only the selected segment is kept, directly reducing file size.
Is AMR compatible with modern devices?
Most Android phones play AMR natively. iOS and desktop systems may require a third-party player or conversion to MP3/AAC. If you need broad compatibility, consider converting with the AMR to MP3 converter.