What is louder (dB rating)?

[BIGMIKE SOCAL]

What is louder (dB rating)? A Chrysler-Bell air raid siren or the German Pintsch Bamag HLS warning siren? Links to the actual specs would also be great...
Thanks,
Big Mike

[der Papst]

The Crysler produces >130dB in 30m distance, the HLS also, the SPL should be similar.
I think both create >160dB at the horns

BTW: Both sirens work without electric supply at full power, i think that is really uniqe.

[acoustics101]

At 138 dB at 100 feet (30 meters), the 180 HP Chrysler siren was the loudest warning device ever built. Here is the website for it.
http://www.victorysiren.com/x/main.htm

What is louder (dB rating)? A Chrysler-Bell air raid siren or the German Pintsch Bamag HLS warning siren? Links to the actual specs would also be great...
Thanks,
Big Mike

[BIGMIKE SOCAL]

At 138 dB at 100 feet (30 meters), the 180 HP Chrysler siren was the loudest warning device ever built. Here is the website for it.
http://www.victorysiren.com/x/main.htm

What is louder (dB rating)? A Chrysler-Bell air raid siren or the German Pintsch Bamag HLS warning siren? Links to the actual specs would also be great...
Thanks,
Big Mike

What about the dB rating for the German Pintsch Bamag HLS warning siren?
Thanks,
Big Mike

[acoustics101]

The word going around is that the HLS is rated at 130 dB at 100 feet omnidirectional. That is still 8 dB less than the Chrysler.


[quote="BIGMIKE SOCALWhat about the dB rating for the German Pintsch Bamag HLS warning siren?
Thanks,
Big Mike[/quote]

[der Papst]

What about the dB rating for the German Pintsch Bamag HLS warning siren?
Thanks,
Big Mike

It's rated at 163-165dB/1m, at 30m the SPL is around 135db - omnidirectional

acoustics101: You compare 4 Chrysler to 1 Pintsch-Bamag, a little bit unfair^^

[acoustics101]

135 db at 30 meters from an omni source? That is hard to believe unless the HLS is considerably more powerful than the 180 HP Chrysler with its 3 dB louder rating over a narrow beamwidth. American Signal's 50 HP omni Cyclone produces only 125 dB at 30 meters (100 feet). It would have to be 500 HP to achieve the 135 dB omnidirectional SPL you are talking about.
http://www.americansignal.com/products/ ... -C-125.php

Sentry Siren's 40 HP 40V2T achieves 130 dB at 30 meters omni by limiting vertical dispersion through a double phased array of choppers and horns. Even it would take 120 HP to achieve the type of output you are referring to.
http://www.sentrysiren.com/warningsiren ... tion=40V2T

The HLS is certainly not a double phased array, so it would have a lower directivity index than the Sentry model, but due to the larger size of its horns, would most likely have a somewhat higher directivity index than the American Signal model. The actual HP requirement would probably be closer to 300 HP than 500 HP. Is it anything close to that?

What about the dB rating for the German Pintsch Bamag HLS warning siren?
Thanks,
Big Mike

It's rated at 163-165dB/1m, at 30m the SPL is around 135db - omnidirectional

acoustics101: You compare 4 Chrysler to 1 Pintsch-Bamag, a little bit unfair^^

[der Papst]

The HLS is not compareable to any other siren because it's a completely different system.
Every other siren uses a fan or a multistage turbine (Chrysler) to produce the airflow when it's needed.

The HLS has a compressor and a very big storage tank.

What do you think why the HLS stores 6000 liters of compressed air?

The compressor is not able to generate the needed air in realtime.
It's also for security in the case of lack of diesel or a broken engine, but the main reason is, the compressor has not enough power.
It's also not necessary to use such a strong compressor because the siren is active for a few minutes and has then hours to recreate it's storage.

The secret of the enourmous SPL is just the pressure.
An axial fan or a turbine has much more airflow but can never reach a pressure of around 20 bar - what the compressor of the HLS does.

I think it would be usefull to write a detailed description of the HLS-system in english...

[acoustics101]

Regardless of its actual dB rating, the HLS is the most impressive siren I've heard about outside of the 180 HP Chrysler siren and Bell Labs 95 HP Big Bertha. It is a very powerful siren capable of being heard indoors from great distances. Even 130 dB omni (outside of vertically stacked arrays) takes more total acoustical power output than a unidirectional source, such as the Chrysler or Penetrator 50.

A directivity index of 13 dB, as in the Chrysler, takes only 1/20 the acoustical power of a truly omnidirectional source to produce the same SPL on axis. The HLS is not, however, a truly omnidirectional source, due to the size of its horns relative to the wavelength and produces more of a doughnut shaped sound field around it, giving it a directivity index in the range of 3-6 dB.

Some so called omni vertically stacked loudspeaker arrays have directivity indices approaching 20 dB, requiring as little as 1/100 the total acoustical power for a given output! That is how they can give impressive SPLs on as little as 4 kW. There is really not much acoustical power involved, but the doughnut shaped pattern around the unit is squashed rather thin. This gives rise to skip and dead zones. When dealing with physics you can never get something for nothing.

I was disappointed by the video of a unit looking similar to the HLS which indicated a mere 100 dB at a mere 20 meters from such a unit. Either the sound level meter had a bad battery, the meter was defective, or the siren's air supply was low.

[Thunderboltlover]

Regardless of its actual dB rating, the HLS is the most impressive siren I've heard about outside of the 180 HP Chrysler siren and Bell Labs 95 HP Big Bertha. It is a very powerful siren capable of being heard indoors from great distances. Even 130 dB omni (outside of vertically stacked arrays) takes more total acoustical power output than a unidirectional source, such as the Chrysler or Penetrator 50.

A directivity index of 13 dB, as in the Chrysler, takes only 1/20 the acoustical power of a truly omnidirectional source to produce the same SPL on axis. The HLS is not, however, a truly omnidirectional source, due to the size of its horns relative to the wavelength and produces more of a doughnut shaped sound field around it, giving it a directivity index in the range of 3-6 dB.

Some so called omni vertically stacked loudspeaker arrays have directivity indices approaching 20 dB, requiring as little as 1/100 the total acoustical power for a given output! That is how they can give impressive SPLs on as little as 4 kW. There is really not much acoustical power involved, but the doughnut shaped pattern around the unit is squashed rather thin. This gives rise to skip and dead zones. When dealing with physics you can never get something for nothing.

I was disappointed by the video of a unit looking similar to the HLS which indicated a mere 100 dB at a mere 20 meters from such a unit. Either the sound level meter had a bad battery, the meter was defective, or the siren's air supply was low.

Although this example is not an HLS siren, it is of a similar issue (not measuring on axis).

Back in April of 2010, I had a brand new SPL meter and a brand new battery in it. I went to record a 2001-DC. I was at exactly 100 feet from the pole (I measured it with a tape measure) and measured it as soon as it went off. I got a 102 dB(C) measure. Only. Just because I wasn't recording on axis. I'm just saying, you can't believe a decibel rating at 100ft from the siren unless it was recorded on-axis.