The arc sound signal in the GMAW contains plenty of welding information, which is relevant closely to arc behavior, melting metal transition mode, arc stability, and it is an important signal source of welding quality control. Aiming at on-line monitoring of welding quality, the modern signals analysis methods were adopted to analyze the time and frequency characteristics of the arc sound signal in short circuit GMAW, and the relationship between arc sound and welding states. Then the concept of tone channe...