The volume of an electric automotive horn is related to the amount of current flowing through the horn coil. When the contact preload increases, the current flowing through the horn coil increases, which makes the volume produced by the horn louder, and vice versa.
Whether the contact pressure is normal can be judged by checking whether the horn's operating current matches the rated current. If the operating current equals the rated current, it indicates that the contact pressure is normal; if the operating current is greater or less than the rated current, it indicates that the contact pressure is too high or too low and should be adjusted.
For cylindrical and spiral electric automotive horns, first loosen the locking nut, then turn the adjusting nut to adjust (turning counterclockwise increases the contact pressure and volume); for basin-shaped electric horns, the volume adjusting screw can be rotated to adjust (turning counterclockwise increases the volume). Do not adjust too hastily; generally, turn the adjusting nut no more than 1/10 of a turn each time.
The volume and tone quality adjustments of an electric horn are not completely independent; they are actually interrelated, so both need to be adjusted repeatedly to achieve the best effect. The sound level of an automotive horn, measured at a distance of 2 m in front of the vehicle and 1.2 m above the ground, should be 90–118 dB(A).
