It would definitely be less than half the output running it at half the speed. That would decrease the output by only 3 dB. Generally it takes about four times the power to run a machine with wind resistance at twice the speed. This would indicate a loss of at least 6 dB. If the frequency dropped be...

Considering that nothing is changed but the number of ports and that the open to closed ratio and total radiating and flow area are the same, reducing the speed would reduce the pressure and thus the output on a siren with a common shaft for the blower and chopper. In the case of a siren with an ext...

Both ACA's Hurricane and Federal Signal's Thunderbolt were good sirens, due to their being able to maintain high output into the lower frequencies. Unfortunately both of them have been discontinued. Here are some videos of them. http://www.youtube.com/watch?v=T9wuwv7j-KE http://www.youtube.com/watch...

Plenty. The Thunderbolt is a somewhat unique siren in that unlike other sirens it maintains its output well into the wind down. This would also be true with the ACA Hurricane, but does it also have adjustable chopper levels? Since the chopper levels are adjustable on a Thunderbolt you can take advan...

From where we live we can hear several of Paducah's Thunderbolt sirens, the Jackson Street firehouse siren being the farthest at about 3 miles and the Concord Elementary siren being the closest at about 1 mile. We can also hear the Tbolts at Lourdes Hospital and the Lone Oak Firehouse, both at a lit...

Paducah, KY and the surronding communities of Lone Oak and Concord does audible testing of their sirens at 1:00 PM on the first Saturday of every month just like clockwork. They used to have nine Thunderbolt sirens, but at least one of them on the southside near Cole Lumber and Don Peck's Moving &am...

Before you mount the horn could you do me a big favor and get a full power SPL reading at 100 feet with the horn off. I've always wondered just how much these horns add to the on axis output. I estimate about 15 dB. I would like to know if I'm right. I was playing around with my T-bolt, I am almost ...

Thanks Mike! This is the most useful information yet about the Pintsch Bamag HLS pneumatic siren. First and foremost, the most important reading is the SPL at 30 meters (100 feet). There is some confusion about the measurement at the mouth of the horn and at 1 meter. Normally you would measure the S...

As far as manufactures go they always go for the unit's maximum SPL. That means getting the on axis reading. Any others testing the output of a unit should do the same at 100 feet. By the time you reach the unit's 70 dB radius it doesn't much matter as long as the unit is not on a hill or in a valle...

From posts to this board within the past year we know this is the case for at least one major manufacturer. Testing in an anechoic chamber can yield accurate results in the near field if the tests are done correctly. Chamber tests should correspond well to dB at 100 feet ratings. However, long range...