GSM, Global System for Mobile Audio File (.gsm)
The GSM Audio file format
GSM is the file extension used for audio files that store strong digital audio data on a computer or mobile device. This file format is generally used by cell phones. The GSM file format was designed particularly for telephone use in Europe and optimized for recording voice audio like any type of telephonic conversation.
Technical details of GSM files
GSM files can be compressed and uncompressed for the purpose of reducing the size of the file. This is done often by using lossy compression. The data can be a raw bit stream in an audio coding format. However, it is generally rooted in an audio data format or a container format with defined storage layer.