Finding/making the loudest horn
 

You folks know me, the inveterate tester.

One of the neat features of my Android-based Nexus 7 tablet is its ability to measure dB of sound, via its built-in microphone and apps like Smart Tools and Android Toolkit.

A couple of decades ago when I was riding motorcycles, I strapped a compressed gas cylinder boat horn to my handlebars, and found it a great safety feature. A blast on that horn, and cars immediately reversed their lane changing intentions. One problem was cylinder cooling when the horn was used, greatly lowering the horn's efficiency.

I replaced the boat horn with an electric compressor twin air horn mounted low on my motorcycle frame. This horn didn't seem as loud. It was high-pitched, and I had doubts about the amount of air put out by its compressor.

Fast forward to today. Now I have a way to measure my horns. The standard is dB loudness three feet or one meter from the horn. Initial impressions are not good. I haven't found an assistant, so I held my Nexus 7 out the open window of each family car at the front corner of the door frame facing the engine compartment, and blew the horn.

Wife's 2012 Hyundai Elantra, stock dual electric diaphragm horns - 86 dB.

My 2006 Scion xB, triple Fiamm electric compressor air horns - a high-pitched and disappointingly weak 86 dB. My cheapo horns suck. I'll do proper testing with a yardstick this weekend. Maybe the horns will sound much louder at the proper distance in front of the cars.

I think I'll spend an afternoon at the shopping center with a yardstick, earplugs, and my Nexus 7.

Hypothesis. The loudest horn will be one with a large (5 gallon?) air tank under high (125 psi?) pressure, with large trumpets.

Hypothesis: Some electric diaphragm horns will do well (110 dB?). Will they be in trucks? Luxury cars?

I'll appreciate your suggestions on which horns to test, theories on the best horns, suggestions on testing methods/procedures.

Loudest horn that would fit under the hood would be a train horn.
I believe they are rated at something like 85dB at 400 meters.

For an electric, the old triple-note Cadillac has a great sound. Mounting position is what matters.

Air horns cannot be beat for sound. But there are limits (highway only on air horns for trucks).

I supplemented my RAM truck horns with the old autobahn standby: the piercing note HELLA pair (see Susquehanna MotorSports - High Performance Vehicle Lighting and Competition Accessories).

I still haven't found an assistant. I did open the hoods and front windows of both cars, and retested their horns by holding the Nexus 7 over the exposed engines, pushing the horn switches. I expected higher dB numbers without the hoods in the way, and the N7 slightly closer to the horns.

Surprise! The wife's 2012 Hyundai Elantra produced 83 dB, and my 2006 Scion xB with Fiamm triple air horns made 86 dB. Those results were the same as (Scion), and slightly less than (Elantra) the results from the front window corners with hoods down.

Tomorrow my wife or daughter should be able to blow the horns, and I'll take measurements of my daughter's car's horns and the other two cars, from three feet in front of the grills, for comparison.

Thanks for the suggestions, Slowmover and oil pan 4. I suspect mfr/distributor claims are like most mfr acceleration claims that seem to be timed with a midget driving down an elevator shaft.

Another idea to try would be to add more horn to your existing horn. Take a funnel and put it on your cell phone speaker while playing music and you will see what I mean.

I built a pair of 6 foot long PVC air horns a while back and they sounded pretty insane. It was never originally intended to be installed on a vehicle but I have seriously been considering putting one of them on my truck. Now for what it's worth it would be a nightmare to try to install something like this on a vehicle without a nice long straight empty frame rail but the concept could easily be scalled down too. The nice thing about it is it was extremely cheap to build, somewhere around $20. But you still would have to come up with some kind of air management to make it function.

I was just considering installing a 5 gallon air tank (which I already have) and filling it with shop air. I don't use my horn that much so I think this setup would work out alright for me. I would probably add a gauge inside the cab so I can keep an eye on the tank pressure and I would also keep my current small direct compressor driven air horns as a back up. I might even install a 3 way toggle so I can use either set as the situation warrents.

Here is a pic of the ones that I made hooked up to an old fire extinguisher as an air source.
https://lh4.googleusercontent.com/-a...230_215949.jpg
They are not quite train horn loud, but they are very low pitched. They sounded kind of like a pissed off battleship. I made these originally to ring in the new year last year. And the 2.5 gallon tank regulated to 50 PSI ran the horns for almost a full minute.

And here is a little diagram that I made that crudely illustrates how they were assembled.

https://lh3.googleusercontent.com/-0...%2520Horn2.png

;)

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Wow, Slow_s10! I need to visit Ecomodder more often. Brilliant, just brilliant. What kind of diaphragm material works best, and how is it cut/shaped/drilled to make the sound?

I use a Hella dual tone airhorn in my Focus...and LOVE IT!
Sounds great and is very loud...

The Internet is my friend. I found several links on how to make air horns using balloons and PVC pipes, plastic Coke bottles, etc. I'll be doing some experimenting and measuring with my air compressor. Eventually, I'll post results.