Sometimes I hear ship whistles when visibility is poor. How LOUD are these things?

Question

Judging by their distance and apparent volume, they must be extremely loud. What decibel range do they usually operate in? Betcha wouldn't want to be standing anywhere near one when it goes off!

Answer 1

It has to be loud for the safe docking of the ship especially at night and like you said poor visibility.  Without the horn, a giant ship can be sailing quietly past you and you wont even know it lol.

Answer 2

The regulations do not specify the sound making device, bell, whistle or gong to meet certain requirements in decibels. Decibels is a measurement of power output. The distance a sound travels is more a function of the frequency, rather than power.

If your boat is under 12 meters, the requirements is that you should carry a device for making an efficient sound signal... pots and pans qualify.

Over 12 meters have more specific requirements, and over 100 meters even more requirements.

There are dimensional requirements for the whistle, and the sound must carry at least a 1/2 mile.

Answer 3

Loud!

Answer 4

I don't have the exact details with me, but in my state, you are required by law to have a horn on board that is audible for a certain distance, that gets bigger with the size of your boat.  In other words, a vessel from 18-22' must have a horn audible to 1/2mile, 22'+ must be audible from 1 mile, etc.  Then there is a cap-off obvioulsy.  Decibals, I have no idea.

Answer 5

Yes you are correct again. They are noisy. If you hear one when your driving...STOP and see how close you are to the water!!

Answer 6

They are air operated. They carry a great distance but are really not that loud onboard. I am not sure of the decibel, but they carry long range frequencies. It goes back to the old days when ships met on the one or two whistle. It determines which side they will pass on or certain ones are used for docking and such.