The Siren Board

im just wondering if there is a way to make a siren the loudest by designing the chopper/rotor a certen way.

RylanPalmese wrote: ↑

Wed Feb 13, 2019 10:43 pm

im just wondering if there is a way to make a siren the loudest by designing the chopper/rotor a certen way.

well the thunderbolt has a small chopper but its special horn design causes the sound to increase not to mention it uses a blower to make the sound increase even more so i think it mostly depends on what horn and what your supercharging it with, but it also can depend on the size of the chopper because if you look at the ACA P-50 for example you will notice it has a pretty big chopper and with the giant horn a ton of sound gets produced.
Or if you take a motor like this https://www.youtube.com/watch?v=ciJtbY-JcaM you might be able to make a pretty loud siren with it, if you design it in a certain way, or if you use a motor thats as big as this https://www.youtube.com/watch?v=pdSKT_8OfKg you might be able to design a siren so loud it will be louder than the Chrysler air raid siren.

So yea it mostly depends on how you are designing the siren whether its the size of the chopper, what horn design you are using and what motor you want to use.

The design of a rotor will effect its output. For example, Federal Signal manufactures their rotors with the vanes (the fins that move the air) in between the ports so the chopper can move in either direction without decreasing sound output: Look at the left picture of the single tone model. You can see that the vanes don't butt up to any one side of the ports.
It isn't the most efficient but is the most plug 'n' play in my opinion.

Then there's directional choppers, where the vanes are located at the end of one of the ports, shown here:
https://www.youtube.com/watch?v=iwRHrSA ... 6h&index=2
This means, for optimal performance, the chopper should run in the direction where the vanes butt up to the side of the ports, as that is where the most air is efficiently moved. It will still work when running in the opposite way, but it won't be as loud.


Having multiple rows of ports on one rotor will also affect its performance, however this is a minor point anyway.

The loudest design would probably be a variation on the pneumatic siren, since a large amount of energy can be turned into sound very efficiently and quickly. The German pneumatic sirens make use of either a disk (F71, etc.) or drum (HLS273) with very tight tolerances and compressed air stored in a tank. Since the air does not need to be moved by the rotor itself, the deign of the siren can focus on tight tolerances and does not need an internal fan, so a siren with a very small and simple rotor (in some cases just a disk with holes) can produce more sound than most standard electro mechanical sirens. Not necessarily the most practical design, but the most potential for an extremely loud siren. As far as normal mechanical sirens, yes, the rotor can be optimized to make the best sound output, in much the same way as optimizing the performance from a vacuum cleaner fan. Compare for example, the rotor of a Federal 508 which is engineered for maximum output (I would assume), and the rotor of my cheap Ebay grey siren, which is engineered for maximum cheapness.

WindowsWhistler2419 wrote: ↑

Thu Feb 14, 2019 12:19 pm

RylanPalmese wrote: ↑

Wed Feb 13, 2019 10:43 pm

im just wondering if there is a way to make a siren the loudest by designing the chopper/rotor a certen way.

well the thunderbolt has a small chopper but its special horn design causes the sound to increase not to mention it uses a blower to make the sound increase even more so i think it mostly depends on what horn and what your supercharging it with, but it also can depend on the size of the chopper because if you look at the ACA P-50 for example you will notice it has a pretty big chopper and with the giant horn a ton of sound gets produced.
Or if you take a motor like this https://www.youtube.com/watch?v=ciJtbY-JcaM you might be able to make a pretty loud siren with it, if you design it in a certain way, or if you use a motor thats as big as this https://www.youtube.com/watch?v=pdSKT_8OfKg you might be able to design a siren so loud it will be louder than the Chrysler air raid siren.

So yea it mostly depends on how you are designing the siren whether its the size of the chopper, what horn design you are using and what motor you want to use.

I'm also pretty sure that the design of the P-50/Cyclone rotor creates alot of drag. So honestly it's rotor design is actually pretty inefficent.

One thing I've always wanted to see is if a rotor with a size such as an STH-10 could be supercharged by some sort of blower. However I think a blower powerful enough to supercharge it would be impractical and uncalled for in a standard outdoor siren system. I'd still like to see how much you could supercharge one though.

Cemoman17 wrote: ↑

Fri Feb 15, 2019 9:27 am

One thing I've always wanted to see is if a rotor with a size such as an STH-10 could be supercharged by some sort of blower. However I think a blower powerful enough to supercharge it would be impractical and uncalled for in a standard outdoor siren system. I'd still like to see how much you could supercharge one though.

I've always wondered about that too - it would be interesting to try it out. It may be awfully loud but I think it would be cool personally.

you would need a blower capable of a ton of CFM to supercharge an STH 10. theres a reason why the thunderbolt only has 1 port.

What about a squirrel cage type furnace blower? those are designed to move lots of air...

Roots blowers will move a lot more air at a lot higher pressure. This is why they're used on superchargers and the like because of the sheer volume of air these things can pump out, especially given their relatively small size. By comparison, you'd need a pretty large centrifugal type fan to move the same volume of air.