[l008com]

So I've got me a small can o' air horn. I use it in my boat. The packaging says it's 112 dB. It is VERY loud. I have to use it to get through the locks every time I go out on my boat. I don't have much room on my boat for a bigger canned air horn. But these small ones don't last long, and don't give any notice that they are running out. They simply STOP working.

Moving on, I found a few nice electric horns, but everyone says they are not nearly loud enough. However they are 108 dB. Googling tells me that two sound sources of the same dB value is adding approximately 3dB to the sound power.

If two small electric horns are going to be only 1dB less loud than my canned horn, thats still more than loud enough to get the attention of all those lock attendants. The benefit of having an electric horn is that it will never run out! And in addition, it isn't going to get lost in the glove box. The horns mount on the deck, and a small button on my dash beeps em. Nice and simple.

But does this math really add up? It seems odd that 108db would be considered too quiet, but 112db would be extremely loud. But there are lots of different sized boats and different sized locks. Maybe they don't realize how small my boat is, and how sufficient 108-112db would be. Maybe I'm underestimating how big a difference 1-3 dB makes? Maybe they underrate the hell out of air horns, so it's really shooting out 120+dB and they just label it 112dB to be safe?

I've heard plenty of opinions on boating forums. Hoping to get some opinions from some people who know more about sound, then about boating.

[l008com]

Can o' Horn:
SuperSound Horn
Doesn't mention db on the site, but the back of the packaging clearly mentions "112db blast"

Electric Horn: (x2)
"SETS" Piezo Electronic Deck Mount Horn
Also doesn't mention db on the site, but I've contact the company and they told me all their horns are 108db.

[Laminar]

dB increase on a logarithmic scale, not a linear one, so 108dB + 108dB != 216dB.

[Doofy]

Twice as loud as 108 = 111. Every three is a doubling in volume.

Get two electric jobbies. Mount them in different places (i.e. one port, one starboard) on top of yer roof or on yer flybridge. Manufacturing variances and the slight phase difference caused by the different mount locations will create a more noticeable sound at a lower level anyway.

And keep yer canned thingy for backup.

[Doofy]

Oh, and stop being so pansy. Do it properly.

Dukes of Hazzard General Lee Dixie Car Horn - WOL430

[mduell]

In addition to doubling the sound power, 3 dB is more or less the smallest discernible difference in volume for humans.

[Spheric Harlot]

^ I'd be careful with statements like that - obviously, that's a matter of training.

0.5 dB can make a huge difference in a mix (subtle though it seems, it can completely change how an instrument works).

In the context of an air horn, though, you're probably right.

[bstone]

Boats. Good times, good times.

[l008com]

So how loud is a 111 db horn? Think it will be loud enough? It's needs to be pretty loud to get the attendants attention. For lots of reasons. This is in the city remember so theres lots of other noises around, including lots of trains that also blow their horns. I'm also about 3 feet above the surface of the water, and at low tide, its about 20 feet up to the platform that had the building on it where the attendants live. And of course at night, you have to wake them up to get through. The other locks in boston are even louder. Major highway, major train station, boat traffic, plane traffic, plus giant blowers for the tunnels all crammed into one tiny spot.

[Doofy]

Originally Posted by l008com 

So how loud is a 111 db horn? Think it will be loud enough?

Truth be told, there's only one way to find out.

[mduell]

Originally Posted by Spheric Harlot 

0.5 dB can make a huge difference in a mix (subtle though it seems, it can completely change how an instrument works).

Are they talking about sound pressure level rather than sound power level?

[Spheric Harlot]

I don't think sound power is that commonly referenced outside of engine design, is it?