1. A spark trainer for welders, comprising: a welding electrode simulator; an electric spark generator which simulates the welding arc and has an output; said output being connected to said welding electrode simulator; a welding object simulation unit, a spark discharge simulating the welding arc being produced between said welding object simulation unit and the tip of said welding electrode simulator, said welding object simulation unit comprising a simulated welding object having a surface along which the simulated welding process is performed; a unit for monitoring the position of the tip of said welding electrode simulator wiht respect to said simulated welding object, which has outputs; a training process control unit having an input, a first output, and a second output, said input of said control unit, connected to said outputs of said unit for monitoring the position of the tip of said welding electrode simulator; said first output of said control unit, connected to said welding electrode simulator; a helmet provided with earphones and connected to said second output of said control unit in order to supply to the welder audio signals indicative of the position of the tip of said welding electrode simulator with respect to said simulated welding object.