A low / hi-tech method used to communicate between two points by utilizing frequencies in the human auditory range.
Typically, the two endpoints will collect ambient noises in the existing environment and create an agreed up rotating collection of sounds to conduct communication.
The purpose of this communication method is to mask its use and existence and to prevent detection by any and all security measures. As the speed / throughput of communication increases, so does the risk of detection. Settings where there is a moderate range of ambient sound are ideal. For circumstances that include quiet settings and extremely loud environments such as concerts make undetectable communication more difficult.
Mitigation techniques include using directional and directed sound to mask the location of transmission. Movement of subjects, especially random, that are the transmission source assist in masking broadcast and transmission.
Typical uses include low bandwidth items such as text communication, low bit rate verbal communication, and even some compressed visual imagery. Realtime video transmission is unrealistic in most circumstances if the objective is stealthy communication.