Convert AAC to AMR — Free Online Converter
Convert Advanced Audio Coding (.aac) to Adaptive Multi-Rate Audio (.amr) online for free. Fast, secure audio conversion with no watermarks or registra...
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Upload your .aac file by dragging it into the upload area or clicking to browse.
Choose your output settings. The default settings work great for most files.
Click Convert and download your .amr file when it's ready.
About AAC to AMR Conversion
AAC delivers music-grade audio at 128-256 kbps, while AMR (Adaptive Multi-Rate) is a narrowband speech codec standardized by 3GPP for GSM and UMTS voice calls. AMR operates at bitrates from 4.75 to 12.2 kbps, producing extremely small files optimized exclusively for human speech. Converting AAC to AMR is necessary when preparing voice recordings for cellular network infrastructure, legacy voicemail systems, or embedded devices that only decode AMR.
Why Convert AAC to AMR?
Telecom equipment, legacy voicemail servers, and many feature phones use AMR as their native audio format. If you have a voice recording in AAC — common when recording on an iPhone — and need to feed it to a VoIP gateway, IVR system, or legacy handset, AMR conversion is required. AMR files are also extremely small, making them practical for transmission over low-bandwidth connections.
Common Use Cases
- Preparing voice recordings for VoIP gateways that require AMR input
- Uploading voicemail greetings to carrier systems that accept only AMR format
- Shrinking voice memos to minimal file size for email attachments in low-bandwidth regions
- Feeding audio to speech recognition systems that expect AMR-encoded input
- Creating audio content for embedded devices with AMR-only decoders
How It Works
FFmpeg decodes the AAC stream, resamples to 8 kHz mono (AMR-NB) or 16 kHz mono (AMR-WB), then encodes using libopencore-amrnb or libopencore-amrwb. AMR-NB offers 8 bitrate modes from 4.75 to 12.2 kbps. AMR-WB extends the bandwidth to 50-7000 Hz across 9 modes from 6.6 to 23.85 kbps. The output file uses the .amr extension with a simple AMR file header.
Quality & Performance
AMR is a speech codec, not a music codec. Converting music from AAC to AMR will sound severely degraded — the narrowband 300-3400 Hz frequency range clips everything above mid-range. For speech, AMR at 12.2 kbps sounds acceptable on phone calls. AMR-WB at 23.85 kbps sounds noticeably better for voice content. Never use AMR for music distribution.
Device Compatibility
| Device | AAC | AMR |
|---|---|---|
| Windows PC | Partial | Partial |
| macOS | Native | Partial |
| iPhone/iPad | Native | Partial |
| Android | Partial | Partial |
| Linux | Partial | Partial |
| Web Browser | No | No |
Recommended Settings by Platform
Spotify
Resolution: N/A
Bitrate: 320 kbps
OGG Vorbis preferred
Apple Music
Resolution: N/A
Bitrate: 256 kbps
AAC format required
SoundCloud
Resolution: N/A
Bitrate: 128 kbps
Lossless FLAC/WAV for best quality
Podcast
Resolution: N/A
Bitrate: 128 kbps
MP3 mono for spoken word
Tips for Best Results
- 1Always use AMR-WB (23.85 kbps) instead of AMR-NB when the target system supports it — the quality improvement for voice is substantial
- 2Pre-process your AAC audio with a high-pass filter to remove frequencies below 300 Hz before conversion, since AMR will clip them anyway
- 3Test AMR output on the actual target device — some older implementations only support specific AMR bitrate modes
- 4For voice memos, record directly in mono at 16 kHz if you know the final output will be AMR, to avoid unnecessary processing
Related Conversions
AAC to AMR serves a specific niche: preparing voice content for telecom infrastructure and legacy mobile devices. Use AMR-WB when available for better speech quality, and reserve this conversion strictly for voice — music will sound unacceptable in AMR.