VOX is a compressed audio format most commonly used to record human speech. Data stored in VOX files in the case of an analog signal is subjected to low-frequency sampling and then saved in digital PCM form. This allows you to record a relatively large amount of audio material in a small file size and transmit them over a channel with a bandwidth of 16 to 32 kb / s. Data in VOX files are encoded using ADCPM (lossy compression).

VOX files were most often used by systems installed in mobile phones. Currently, it is a rare format.