Thunderbolt Siren Coverage Area

[AST128_RyanK]

For the Thunderbolt siren, how far from the siren head does the sound project and what is the DB rating @100 feet?

[Chicagosiren-hunters]

The Thunderbolt 1000T/1003 has 126 Db's @ 100', and the Thunderbolt 1000 has 127 Db's @ 100'. Also, there was a rumor that a Thunderbolt 1000 could reach 131 Db's with an A2 6M blower.

[connerdstines]

Also, there was a rumor that a Thunderbolt 1000 could reach 131 Db's with an A1 6M blower.

Wasn't that the 5M A2 blower? It did have the highest CFM and pressure rating of all of them.

[Chicagosiren-hunters]

Oops...I meant to say A2. Sorry, I'll fix that.

[coastalsyrolover]

Yes it's a 5M A2. After a LONG conversation with federal signal I have found that the Thunderbolts never got a true rating but instead used a rate of diminishment formula to measure it (Instead of actually measuring it at 100 feet.) The 5M blower for the single tone heads don't really affect it all that much except the 6M might due to the pulsating sound of the slower blower. If you compare the sound of the 2001-130 and the thunderbolt (Which the 2001-130 was built at a time when they could get a more accurate measurement and is actually... As quoted by FS... 130 @100.) The single tone bolt is for sure louder. And carries further. The dual tone heads are affected by the bigger blower though. (Also please note that any noticeable change in sound usually has to have a 2-3 DB jump for our ears to notice. Quote by a friend who is studying sound.) But yea again the bolt never got a TRUE rating and with the adjustable frequency it can carry and or penetrate more. And yes... Weather it be the "Beast bolt" (Single tone) or "Bite bolt" (Dual tone) They are both LOUD!!!!!

[AST128_RyanK]

Yes it's a 5M A2. After a LONG conversation with federal signal I have found that the Thunderbolts never got a true rating but instead used a rate of diminishment formula to measure it (Instead of actually measuring it at 100 feet.) The 5M blower for the single tone heads don't really affect it all that much except the 6M might due to the pulsating sound of the slower blower. If you compare the sound of the 2001-130 and the thunderbolt (Which the 2001-130 was built at a time when they could get a more accurate measurement and is actually... As quoted by FS... 130 @100.) The single tone bolt is for sure louder. And carries further. The dual tone heads are affected by the bigger blower though. (Also please note that any noticeable change in sound usually has to have a 2-3 DB jump for our ears to notice. Quote by a friend who is studying sound.) But yea again the bolt never got a TRUE rating and with the adjustable frequency it can carry and or penetrate more. And yes... Weather it be the "Beast bolt" (Single tone) or "Bite bolt" (Dual tone) They are both LOUD!!!!!

Long story short, compared to the FS 2001-130 the Thunderbolt covers a wider area and is louder.

In the right conditions could the 1000 reach roughly 2 miles around the siren and the 1000t and 1003 reach roughly 1.5 miles around the siren?

[coastalsyrolover]

Yes it's a 5M A2. After a LONG conversation with federal signal I have found that the Thunderbolts never got a true rating but instead used a rate of diminishment formula to measure it (Instead of actually measuring it at 100 feet.) The 5M blower for the single tone heads don't really affect it all that much except the 6M might due to the pulsating sound of the slower blower. If you compare the sound of the 2001-130 and the thunderbolt (Which the 2001-130 was built at a time when they could get a more accurate measurement and is actually... As quoted by FS... 130 @100.) The single tone bolt is for sure louder. And carries further. The dual tone heads are affected by the bigger blower though. (Also please note that any noticeable change in sound usually has to have a 2-3 DB jump for our ears to notice. Quote by a friend who is studying sound.) But yea again the bolt never got a TRUE rating and with the adjustable frequency it can carry and or penetrate more. And yes... Weather it be the "Beast bolt" (Single tone) or "Bite bolt" (Dual tone) They are both LOUD!!!!!

Long story short, compared to the FS 2001-130 the Thunderbolt covers a wider area and is louder.

In the right conditions could the 1000 reach roughly 2 miles around the siren and the 1000t and 1003 reach roughly 1.5 miles around the siren?

Yes. The thunderbolt covers a wider area (Which I can attest to considering I could hear a thunderbolt through a closed house (Meaning doors and windows) and couldn't hear the closer 2001s until we opened the front door. FS also confirmed that suspicion). In the right conditions this happened: https://www.youtube.com/watch?v=JXrOaTiOJDU
Turn your volume all the way up (Video credit to TommyBNSF). This recorder picked up this thunderbolt facing just slightly north of it from 9 miles away. You can kind of hear the 2001s but not as clear as that thunderbolt. (Note though: The audio has been boosted so you can hear it clearer.)

[AST128_RyanK]

Yes it's a 5M A2. After a LONG conversation with federal signal I have found that the Thunderbolts never got a true rating but instead used a rate of diminishment formula to measure it (Instead of actually measuring it at 100 feet.) The 5M blower for the single tone heads don't really affect it all that much except the 6M might due to the pulsating sound of the slower blower. If you compare the sound of the 2001-130 and the thunderbolt (Which the 2001-130 was built at a time when they could get a more accurate measurement and is actually... As quoted by FS... 130 @100.) The single tone bolt is for sure louder. And carries further. The dual tone heads are affected by the bigger blower though. (Also please note that any noticeable change in sound usually has to have a 2-3 DB jump for our ears to notice. Quote by a friend who is studying sound.) But yea again the bolt never got a TRUE rating and with the adjustable frequency it can carry and or penetrate more. And yes... Weather it be the "Beast bolt" (Single tone) or "Bite bolt" (Dual tone) They are both LOUD!!!!!

Long story short, compared to the FS 2001-130 the Thunderbolt covers a wider area and is louder.

In the right conditions could the 1000 reach roughly 2 miles around the siren and the 1000t and 1003 reach roughly 1.5 miles around the siren?

Yes. The thunderbolt covers a wider area (Which I can attest to considering I could hear a thunderbolt through a closed house (Meaning doors and windows) and couldn't hear the closer 2001s until we opened the front door. FS also confirmed that suspicion). In the right conditions this happened: https://www.youtube.com/watch?v=JXrOaTiOJDU
Turn your volume all the way up (Video credit to TommyBNSF). This recorder picked up this thunderbolt facing just slightly north of it from 9 miles away. You can kind of hear the 2001s but not as clear as that thunderbolt. (Note though: The audio has been boosted so you can hear it clearer.)

Absolutely remarkable!

[coastalsyrolover]

Yea they don't mess around. Just too bad they never got a like... "real" rating. Personally I don't for a second doubt that the single tone ones exceed 130 @100. But that's just my opinion and what my research leads me to believe. I am sure others disagree with me on that but... Boy they are loud. Dual tone ones are VERY harsh and can perform pretty well too but (and uncommonsense pointed this out in an earlier thread) that the dual tone has a canceling effect and diminishes faster (From what I understood.) Anyways yea... This is all based on conversations, videos and my personal nerdy research that involved remembering what a single tone bolt sounded like up close compared to the 2001s. I don't have the siren expert badge but this is just what I have kind of concluded as for as the bolts go. Maybe Murrfarms and Holler can chime in and give their opinion as they seem to like thunderbolts (Single and dual tone) a lot.

[DJ2226]

The simple answer is that there is no defined dB rating, and it varies from unit to unit.

When CD was still a thing our city got ratings from FS&S and FS. Those didn't list the 100' SPL, but the 70 dB range which is more important with any siren. They rated them, at that point in time Series A2 or B 1000ATs with 5/6 port choppers at level 6 and 4M blowers, to have an effective coverage radius of 4500'. They had the same ratings with the older units with the 5M blowers. Swapping the blowers around yields a slightly louder siren, but from what I've heard in person I couldn't tell the difference, 5M vs 6M. I've actually heard some that in some instances the 4M blown siren would be louder even with the blower not forcing as much air as the 5M

Now these sirens could vary in pitch, so as you change it you'll change the SPL of the siren and the way the sound propagates. For example a 1000 putting out 575 Hz will carry differently than if the same siren was putting out 485 Hz. You can see this on the electronic side with Whelen. The upped the pitch of their sirens to 560 Hz from 435 Hz (455 and 530 Hz were also used on that controller) making sirens like the 2910 and 4004/Vortex R4 jump from 126 dB to 129, and I can tell you from personal experience that it makes a big difference with our 2810s and some of the Vortexes over yonder. With that said even when the siren could produce different pitches while sustaining volume theoretically (Thunderbolts are technically louder higher pitched as more air can flow through the head, I've heard this in person) the change in pitch dramatically changes the performance. This is why Whelen tests their sirens in alert to get those ratings, and it is also the reason the Equinox and 508 will perform the same, if not better, then the 2001-130 even though they're "quieter."

The main mechanisms I've seen that effect the way sirens perform are atmospheric absorption and ground impedance. The first one is the basic one, where the higher the pitch, the fast a sound will be absorbed into the air the second one is the absorption and scatter of sound along the ground. It's lowest at 500 Hz and stays constant as you go from 500-1000 Hz. It acts like the graph of a polynomial function with the leading coefficient's exponent being even and positive, makes a "U". 500 Hz is the sweet spot for sirens, although you could make the argument that it blend in too much with the environment. I mention this because of the dual tone vs singe tone mentioned above, but from a different perspective with the cancellation stuff aside. In this case with a 5/6 port 'bolt running at chopper level 6, half, give or take, is making ~ 575 Hz and the other ~ 690 Hz. The high tone side of the siren is absorbed into the air faster.

Even though it's kind of off topic, there was mentioned a Thunderbolt being heard from 9 miles away. I've heard a 2909 from about 10 miles away when I was recording one of our sirens. That was the closet one on Ft. Benning, GA to where I was. Pierce Chapel Rd. in Columbus, GA and 11th Airborne Rd./Moye Rd. in Ft. Benning, GA