At the local car show I metered the shocker horns, all facing down @ 150 psi.
This was with a fairly new TermLab sensor(measures pressure, not just loudness)
With the meter in the horns they did a 124.9 db run. This is pressure, not the loudness that is advertised.
Nice:)
Do you have mesured the loudness ??
I assume they used the pressure sensor? (the black box with suction cups)
if so, that isn’t accurate since it is only capable of measuring 80Hz and below. unless you have a ship horn, that won’t register correctly. 
the audiocontrol with the calibrated mic is another matter though. that can measure the full frequency range so you can measure SPL from ship horns to hand held air horns.
^ exactly. I will also add that sound is measured in pressure not “loudness”. It is called SPL (Sound Pressure Level). So I’m not quiet sure what you meant by “This is pressure, not the loudness that is advertised”.
I’m not sure what I meant when I said that either, I had a long day yesterday.
I think I was trying to say thats what the meter read but I’m sure it was not fully accurate or the best conditions to be testing it.