As you would probably guess, the noise level in my truck cab is higher than that in most personal vehicles. This is in spite of improved sound-proofing in the relatively new model I drive. On surface streets the noise is predominantly from the engine during gear shifts. When I’m at cruise speed on a level open road (typically on an interstate or major highway with two or more lanes in each direction, in sparse traffic, usually in a rural area), engine noise is reduced and replaced with tire noise that is a roar when heard outside the truck. An additional contributor to cab noise is wind. Cab noise is significantly increased when I’m driving into wind. Add in playing my radio, and you may wonder how well I can hear an emergency siren or the horn of your vehicle.
An important variable is the type of horn in a personal vehicle. Horn sounds in personal vehicles vary from the louder blaring to a more muted monotone. The former penetrates the cab more effectively. On surface streets, I can hear sirens well. However, if you are behind or even alongside the rear half of my trailer, I may or may not hear your horn well. On the open road a siren or horn is considerably less audible, especially when the source is in those rearward positions.
What I would like you to remember is this: In general, if you ever feel in danger around my truck take immediate evasive action, then sound your horn to warn me. Do not depend on immediate corrective action from me. By the time I’ve heard your warning, it could be too late.
Do not rely solely on your horn to warn off a truck driver—take immediate evasive action first.