The first part of the article described the methodology for full-scale experiments conducted to determine optimal parameters of high — and low-volume sound signalling devices of locomotives. At the first stage, the propagation of sounds of various frequencies over railway tracks was studied. The clarity of perception of these sounds against the background of their masking by a characteristic transport noise was studied at the second stage. However, it was much more difficult to create a hardware and test such devices that would meet the set requirements. The article below describes the solution of this problem.