Single-core cable on the bridge why the buzzing
Of course to vibrate. The conduction conductor is the same current absorption, the opposite current repulsion.
When the current is too large will have a magnetic field, when placed near the metal body, it may produce 50HZ AC sound.
The cable is sounded in the bridge because of the mechanical properties of the current. When the cable passes through the current, the cable will vibrate due to the mechanical effect of the current, so the cable will strike and hit the sound. Of course, if the current is very small, the cable will not produce too much vibration amplitude, it will not hit the sound and the impact of the bridge.
