What is a GSM file?
The GSM file format, more technically known as GSM 06.10 or Full Rate, represents a specialized audio compression standard engineered explicitly for crystal-clear human speech. Originally developed as the core codec for the groundbreaking Global System for Mobile Communications (GSM) network, this technology was instrumental in popularizing mobile phones worldwide. As an audio file type, its primary association is with Global System for Mobile Audio Format Files.
A GSM file is encoded with a lossy CBR (Constant bitrate) sound compression codec. The sample rate in a GSM audio file is 8000 samples/second whereas the data rate is around 13 kbps. The bitrate within the GSM files ensures quality during voice recording. Moreover, the GSM file format is also known as the global standard format to be used in mobile phones and WAV files can also be easily encoded using a GSM file format. Any issues with a GSM file can be easily resolved by the user himself without going to an expert.
Users can also convert GSM files into MP3 and MP4 formats.
Brief History of GSM File Format
GSM is an audio file format that was created for internet telephony in Europe. It was developed by European Telecommunications Standard Institute (ETSI) to be used as a 2G digital cellular used in mobile phones and tablets. Today it is used to store recordings of telephone conversations and voice messages.
Key Characteristics of GSM Files
| Characteristic | Description |
|---|---|
| Speech-Optimized | Excels at compressing human voice with high intelligibility but is poor for music or complex sounds. |
| Highly Efficient | Achieves impressive compression with a very low bit rate (13 kbps), making it ideal for bandwidth-constrained environments. |
| Ubiquitous in Telephony | Served as the foundational codec for 2G GSM networks and is still used in some voicemail systems and professional audio recorders for dictation. |
| Low Fidelity | The audio quality is narrowband (mono, 8 kHz sample rate) and has a distinct, slightly robotic or “tinny” sound characteristic of early digital calls. |
GSM File Format Specifications
GSM work on a structured network which consists of the following sections:
- Modulation : It is a process of transforming input data into a format that can easily be transmitted. The transmitted data is demodulated at the receiving end
- Transmission rate : GSM is a digital system that has an over the bit rate of 270 kbps
- Uplink Frequency Range : 933-960 MHz
- Downlink Frequency Range: 890 – 915 MHz
- Channel Spacing : It means the spacing between adjacent barriers which should be about 200 kHz
- Duplex Distance : It is the space between uplink and downlink frequencies which should be 80 MHz
- Speech Coding : GSM uses Linear Predictive Coding (LPC). LPC compresses the bit rate. When the audio signal passes through a filter and mimics the vocal tract. GSM encode speech at 13kbps
| Audio compression format | Algorithm | Sample rate | Bit rate transform | Latency | CBR | VBR | Stereo | Multichannel |
|---|---|---|---|---|---|---|---|---|
| GSM-HR | VSELP | 8 kHz | 5.6 kbit/s | 25 ms | Yes | No | No | No |
| GSM-FR | RPE-LTP | 8 kHz | 13 kbit/s | 20–30 ms | Yes | No | No | No |
| GSM-EFR | ACELP | 8 kHz | 12.2 kbit/s | 20–30 ms | Yes | No | No | No |
FAQ
Q1: Can I play a .gsm audio file on my modern computer?
A: Yes, but you may need a dedicated media player like VLC or an audio converter, as support isn’t always native in operating systems like Windows or macOS.
Q2: Is the GSM format still used today?
A: While largely superseded by more advanced codecs like AMR-WB (HD Voice) in modern 4G/5G calls, GSM is still found in some legacy voicemail systems and as an export option in audio software.
Q3: Is GSM audio quality good for music?
A: No, the GSM format is specifically designed for speech and will significantly degrade the quality of music, resulting in a muffled and compressed sound.
Q4: What’s the difference between a GSM network and a GSM file?
A: The GSM network is the cellular communication standard, while the GSM file format is the specific audio codec used within that network to encode voice calls.
Q5: Why would I use a GSM file today?
A: Its primary modern use is for voice recording in applications where small file size is critical and high fidelity is not, such as dictation, some voice memo systems, and specific telephony logging.
