The acoustic signal transmission includes electrically synthesizing an audible sound signal and an insertion signal to generate a synthesized sound electrical signal at the sending side, transmitting the synthesized sound electrical signal, and extracting the insertion signal form the synthesized sound electrical signal at the receiving side. The extracted signal may be used for controlling machines or for transmitting information. The acoustic signal represented by the synthesized sound electrical signal can be heard by human ears in the same way as the audible sound signal, while the synthesized insertion signal cannot be detected by human ears. The synthesized sound electrical signal can be transmitted as a sound wave in air space, as electrical signals through a transmission line or as radio signals such as infrared and electromagnetic waves. The synthesized sounds may also be transported or distributed by recording on recording media such as compact disc and DVD.