Most of the horns I have looked at are 113 DB , which I believe is the same as stock. I did see some 300DB, but now I have to search for them. If I can find them again I'll give them a try.
Ah yea no
There is ONLY one correct way to measure Db of a thing like a horn that is DOT approved aka meant for the road or FRA (trains) Specific humidity and distance (100 feet). There is a reason for this, sound travels at different speeds depending on its "tone" or rather wave length or pitch, some of those can interfere with others and some others can amplify others. This is why you have DUAL tone horns BTW. You can make all sorts of noise up close but far away you want to have the right sound = loud vs crappy. Remember we need people inside cars with the radio on to hear it. Those BS tests are from just a few feet away. FFS a fire cracker is about 130DB within a few feet
The stock horn is actually about 75 to 80 DB. Measured correctly
Most of those aftermarket non bs brands are fairly accurate but usually never top 110db from a few feet but are usually LESS than stock horns measured from the correct distance. The Porsche Cayenne we have has a REALLY NICE small horns that are about 104 DB but from 100 feet away its probably no more than 90. VERY SMALL for what they do.
My train horns are legit 146 DB but from 100 feet away its only 108.
Oh btw, the loudest recorded sound in history was 310 DB and was that epic volcano eruption heard around the earth many times.
1883 eruption of Krakatoa
So unless your horn literally blew out the windows of all the buildings within 20 miles and was more powerful than a space shuttle launch I am extremely skeptical of your claims. Btw the space shuttle launch was 136 from a distance but up close is about 260 DB.
Here are some good videos
