GSM vs SOX
A detailed comparison of GSM Audio and SoX Audio — file size, quality, compatibility, and which format to choose for your workflow.
GSM Audio
Audio FilesGSM 06.10 is a speech compression standard designed for the Global System for Mobile Communications. It encodes speech at 13 kbps using Regular Pulse Excitation with Long Term Prediction, optimized for voice intelligibility over cellular networks.
About GSM filesSoX Audio
Audio FilesSoX (Sound eXchange) native format is used by the SoX command-line audio processing tool as an intermediate representation. It preserves full sample precision and metadata during complex audio processing chains involving multiple transformations.
About SOX filesStrengths Comparison
GSM Strengths
- Tiny bitrate (13 kbps) — hours of speech in a few MB.
- Speech-optimized — clear voice reproduction.
- Universal cellphone decoder adoption 1991-2015.
- Stable since 1987.
SOX Strengths
- Preserves full PCM precision between SoX steps.
- Proprietary but documented format.
- Useful as pipeline intermediate in audio scripts.
Limitations
GSM Limitations
- Speech-only — music sounds distorted.
- 8 kHz sampling — narrowband, muffled by modern standards.
- Legacy — LTE VoLTE moved to AMR-WB, Opus, or EVS.
- Tooling outside telecom is sparse.
SOX Limitations
- Niche format — almost no tool outside SoX reads .sox.
- Superseded in most workflows by WAV or FLAC for intermediates.
- Rare in production deployments.
Technical Specifications
| Specification | GSM | SOX |
|---|---|---|
| MIME type | audio/gsm | audio/x-sox |
| Extension | .gsm | .sox |
| Codec | GSM 06.10 (RPE-LTP) | Raw PCM (SoX's native intermediate) |
| Sample rate | 8 kHz | — |
| Bitrate | 13 kbps | — |
| Associated tool | — | SoX (Sound eXchange) |
| Formats SoX handles | — | 30+ (WAV, AIFF, FLAC, MP3, OGG, etc.) |
Typical File Sizes
GSM
- 1 min of voice ~100 KB
- 1 hour voicemail archive ~6 MB
SOX
- 3-min PCM 16-bit stereo intermediate ~30 MB
- 1-hour 24-bit intermediate ~1 GB
Ready to convert?
Convert between GSM and SOX online, free, and without installing anything. Encrypted upload, automatic deletion after 2 hours.
Frequently Asked Questions
GSM (GSM Audio) is an audio file format used to store sound recordings — music, voice, podcasts, sound effects. The format defines how the audio samples are compressed (or stored raw), what bitrates are supported, and how metadata such as title, artist, album, and cover art is embedded. It is part of the audio files family.
SOX (SoX Audio) is an audio file format used to store sound recordings — music, voice, podcasts, sound effects. The format defines how the audio samples are compressed (or stored raw), what bitrates are supported, and how metadata such as title, artist, album, and cover art is embedded. It is part of the audio files family.
VLC, foobar2000, and the default media players on Windows and macOS handle GSM natively. On mobile, iOS Music and Android media apps vary in their support — popular formats work everywhere; niche ones may need a dedicated app. If playback fails on a device, converting to MP3 or AAC usually solves it.
VLC, foobar2000, and the default media players on Windows and macOS handle SOX natively. On mobile, iOS Music and Android media apps vary in their support — popular formats work everywhere; niche ones may need a dedicated app. If playback fails on a device, converting to MP3 or AAC usually solves it.
Upload the GSM to KaijuConverter and pick MP3, WAV, FLAC, AAC, OGG, or any other target. Our FFmpeg pipeline decodes the audio and re-encodes to the target format at sensible default bitrates (VBR ~190 kbps for music, 96 kbps for speech). Metadata and cover art travel with the audio where both formats support them.
GSM can be lossy or lossless depending on the specific variant. Lossy variants (smaller files) discard some audio detail during compression in ways tuned to be inaudible; lossless variants preserve every sample exactly but produce larger files. For distribution, lossy at high bitrate is standard; for archival, lossless wins.