The GSM audio file format was created for telephony use in Europe, therefore it is mostly used for telephone quality voice. Compression and decompression are slow and the quality is not great, but the main problem is that the raw GSM format is not supported by most audio players. Converting to an intermediate uncompressed format allows you to use voice recording in any application.
In fact, the GSM format is not as simple as Wikipedia describes it. According to the 6.10 specifications, it is an 8kHz file with a bitrate of 13kbps. This is only true for raw files with a .gsm extension. The GSM codec from Microsoft supports many more sample rates, and the compressed data are stored in a RIFF container with the .wav extension.
There are quite a few GSM converters, but most are associated with IP telephony and can open files one at a time. For batch conversion of records from Asterisk or similar system you need a more advanced converter. Audio Converter Plus is the all-in-one audio conversion software, which can help you convert your GSM files easily with excellent music quality. As an output format, it allows you to use both lossy and losless formats.
1 Download GSM To WAV ConverterDownload Audio Converter Plus from our site: https://www.abyssmedia.com/downloads/audioconverter.exe
Run the downloaded file audioconverter.exe to start installation, which is fast and requires no knowledge. After installation, double click on the converter icon, you will see the user interface below.
3 Add GSM Files To Conversion List
Add the GSM audio files by using "Add File" or "Add Folder" buttons or simple drop GSM files into the converter.
4 Select the output folder
At the right bottom field you can see an Output Folder option. Click on the "Browse" button to set an output path, which will be the destination folder of converted WAV files.
5 Set Output Format
You can select any output codec from the list: M4A, WAV, MP3, WMA, OGG or AMR.
6 Start Converting
Click on the "Convert" button, the conversion task will be started immediately. After the process is completed, you will see a flashing converter icon on the taskbar.