This article originally appeared in Horn & Whistle Magazine, Issue #88, Summer 2000.
Reprinted here courtesy of Horn & Whistle Magazine.

Thursday, October 28,1999 was a day I will never forget for the rest of my life. I finally had the opportunity to hear a Chrysler 180 HP siren close up. During the several years that I have subscribed to Horn & Whistle, I have called and corresponded with a few of you, most frequently with editor Harry Barry. Last year, while returning from a pipe organ assignment in Michigan, I met Harry for the first time since I was driving right through the northeast comer of Pennsylvania and my route took me within a few miles of his home.

Harry definitely has what must be one of the most diversified collections of acoustical signaling devices anywhere. With great interest I looked at his impressive assortment of big and small whistles, many different locomotive air horns, and even a lighthouse diaphone fog signal. At that time he showed me among other things his Chrysler air raid siren, although it was not yet fully operational so I could only look and try to imagine what it might be like. Now, finally, I had a chance to see and hear it in full operation.

When I knew that I would again be making a trip to Michigan the last week in October, I called Harry and arranged to visit him. I looked forward greatly to seeing and hearing his now fully restored and operational Chrysler siren. From time to time I've seen mention of these sirens in Horn & Whistle, and Harry had an article about this siren a while back as I recall, but although the article gives a good description of the machine, I wondered what does this thing really sound like? Perhaps many of you other readers have also wondered about that. Therefore, I will now do the best I can to convey an accurate impression of what is most likely the loudest, and indeed perhaps the ultimate, commercially produced audible signal device ever created.

Although I frequently spoke the Finnish language as a young child because of my ancestry, I nevertheless was born in the USA and went to school here. Therefore I consider that my English usage skills are at least as good as the next person's. However, I can think of no accurate way to describe the power of the Chrysler siren with words. So rather than even attempting that, I think it is better to chronicle the observations and impressions that I had while experiencing this most unusual signal and let you infer from that what its sound is like.

When I arrived at Harry's home that afternoon, I noticed the siren, beautifully restored and painted in a nice glossy red, looking very impressive and majestic mounted on its own special trailer. Yes, that's right! This siren requires a trailer for transportation. Because of the proximity of neighbors, Harry told me that we'd have to move the siren to a very remote location. We then proceeded to an isolated road near a reservoir perhaps ten miles away from his house. As we drove to his siren testing site, I could feel Harry's truck bucking and straining as it pulled the heavy machine along. Already this should tell you something.

Here is a siren which requires a trailer behind a truck to be transported from one location to another. Even the idea that sounding it requires it to go to a very isolated location miles away from other people suggests that it must be very loud indeed. Anyhow, as Harry and I rode with our 5000+ lb load behind us, he told me a little more detail about some of his earlier experiences with it. Finally, seemingly miles away from anything or anyone else in an isolated rural area we stopped and pulled over beside the road. First Harry had to turn the trailer around because he wanted the siren to point away from the town. Towing this monster around for a while now has given Harry lots of practice and he does an expert job of maneuvering the trailer. If you've ever tried to back a trailer into position, you'll know that there is more to that than meets the eye. Anyhow, with the siren now parked beside the road and facing away from town, Harry then started its engine. For those of you unfamiliar with this monster siren, here is the briefest of descriptions. A 180 HP Chrysler V-8 industrial gasoline engine drives a three-stage centrifugal compressor at 4500 RPM. The compressor housing appears to be about 42 inches in diameter and 18 inches deep. The entire output of the compressor section then enters an integral circular chamber to which are attached six cast aluminum horns. The horn throats are arranged in a circular pattern at 60 degree intervals. Just inside this circular chamber is a heavy circular steel plate with six ports. As this plate rotates (also at 4500 RPM), the ports alternately open and close the throats of the six horns. This modulates or chops the air flow from the compressor section into a series of pulses which constitute a high amplitude sound wave.

The pressure in the Chrysler siren is not actually all that high, rising only to about seven PSI; however the quantity of air moved is very great indeed, probably several thousand CFM. A centrifugal compressor is really a specialized form of blower, and blowers typically move large quantities of air. Since the sound pressure level of a signal device which modulates an air stream is a function of both pressure and flow, we can see that a signal device which moves large quantities of low pressure air can indeed compete favorably with a signal which moves smaller quantities of higher pressure air.

Anyhow, after Harry started the engine, he let it idle for several minutes to warm up. At this point, it sounded like any normal engine idling, except that there were no mufflers on the two engine exhaust pipes. When the engine had warmed up sufficiently, Harry then threw the clutch engaging the compressor and siren rotor plate. Although at this point the engine was probably only idling at 500 RPM, the siren began to produce sound, an enormously powerful and deep tone, not unlike the bass of a pipe organ flue pipe but much louder and with more harmonic development. Interestingly enough, although this low tone made the air pulsate, it was not unpleasant to the ear, even though I could feel the sound in the air. Finally, determining that everything was ready, Harry flipped a switch which activated a solenoid attached to the engine throttle.

At this point, the engine began to pick up speed and reached top speed in about ten seconds. I stood at a respectful distance to the side and behind the huge siren and held my ears. As the machine approached rated speed, I could actually feel the pavement of the road vibrate. The sound level even behind the siren and with my ears stopped was unbelievable. The maximum rated pitch of this siren is around A 440 or so, considerably lower than the pitch of most air raid sirens and especially vehicle sirens. I walked around a little, still staying behind the siren and still staying about 30 feet away from it. No matter where I went, I could feel the ground vibrate. At first I thought I was feeling mechanical vibration from the engine and the compressor, but the rubber tires of the trailer would have absorbed that. The vibration of the ground was strictly the result of the siren sound output. Finally Harry flipped the switch to the other position and the siren slowed down until again it reached idle speed.

Then he invited me to try it. I stepped up on the trailer and went to the small control panel on the side of the engine compartment to flip the switch. Although I now wore Harry's hearing protectors, it soon became evident that they weren't sufficient and I slid a finger under each earmuff to hold my ears. At this point I was standing probably about seven feet behind the compressor-siren assembly. Suddenly, everything else disappeared from existence. The engine was running wide open at 4500 RPM with no mufflers on its exhaust, but I never heard it at all even though it was right beside me. There was only this incredible tone of A 440 which obliterated everything. I felt the sound in the air; in my face, in my hands, in my whole body. I looked briefly at my clothes and saw the fabric appeared blurry. My garments were vibrating at this same frequency! I even felt the sound in my beard and moustache. In a very short time of only a second or so, it began to be extremely uncomfortable standing there on Harry's trailer right beside this gargantuan siren. My nose and the area just below my eyes began to ache slightly and I noticed my eyes beginning to tear over, not from emotion but evidently from the incredible vibration that enveloped me completely.

I felt as though I could reach out and touch the sound, or lean on it or even sit on it, maybe even pick it up with a shovel or swim in it. It was that physically real, as though the sound itself had taken on a new and somewhat viscous, liquid form. Now, I had to figure out how to shut this thing down without removing my fingers from my ears. Finally, I reached up and hit the switch with my right elbow! Then I stepped down and back as the siren once more slowed to idle speed.

At this point Harry asked if I wanted to hear how the siren sounded from up front. Remember that until now I had been either behind or beside the siren, but always at a respectful distance from those killer horns on the front section. He also suggested that I stand at a considerable distance, which I would have done even without being told. As Harry positioned himself at the controls, I ran ahead down the road until I was about 200 feet away. Then I turned to signal him and he revved the big siren up once again.

Now, many of you have a set of two-, three-, or five-chime railroad locomotive horns, and probably every one of us has been close to a railroad crossing when a train has approached. I know that I have stood a hundred feet ahead of three- and five- chime railroad horns several times. There's no question that these are really loud if you stand directly in front of them even 100 feet way. But, although annoyingly loud, at that distance you can tolerate a multi-chime railroad horn without ear protection although I wouldn't recommend it. However, at two hundred feet, the Chrysler siren's tone is, when standing in front of it, so powerful that I could not, although I tried, take the sound for more than maybe a second or two before I had to hold my ears. And remember, this siren makes just a single note, not a multi-tone chime sound.

From many years of restoring pipe organs, I have learned to analyze pitches and sound quite accurately by ear, and I can therefore tell that the fundamental or first harmonic of the Chrysler siren is extremely powerful. Interestingly enough, however, the sound of the big siren does have a considerable amount of harmonic development. The second and third harmonics are quite prominent. I also noticed that the entire band of harmonics from the fourth through the twelfth are very strong also. When sounding its top pitch of approximately A 440, this siren has a sound somewhat like that of an air horn, although without the really sharp, biting edge that a horn under full pressure develops. Nevertheless, there are frequencies present in the siren output that approach 3,000 Hz or more. At two hundred feet directly in front of the unit, these add a very piercing and sharp quality to the sound, which along with its incredibly strong fundamental pitch make its sound painfully loud even at that distance.

Finally, Harry shut it down for the last time as it was becoming evening, and we returned to his place. I could not get over how this thing sounded. I have never in my 55 years of existence heard anything even remotely close to the sound of this humongous howler before, and I truly believe, as Harry had stated, that under favorable conditions one could hear a Chrysler siren 50 miles away. It certainly adds an entirely new impression and understanding to the words loud sound. Comparing this to a normal fire engine siren is like comparing an elephant to a mouse. Harry at that point went on to tell me about another Horn & Whistle member who has a similar siren and tested it in or near his garage, where it shattered all of his fluorescent lights. He also mentioned that if you placed a leaf just before one of the monster siren's six horns, the main portion of the leaf would rapidly disintegrate and leave only the stem and veins. We then went on to speculate about what would happen to any person unlucky enough to be directly in front of the siren horns when operating at full power. Although we certainly aren't going to try it, I have no doubt that it would do serious and possibly even fatal structural damage, and accomplish that in a relatively short time.

In the same sense that ultra-low temperatures and very strong electrical fields create entirely different environments and cause some substances to exhibit markedly strange properties, I believe that at close range the sound of this enormous siren would likewise create a new and different environment within which some ordinary things would exhibit new and different behavior. Certainly for me, the idea of sound as being an all-pervasive and tangible entity was a concept that I never had until now. (Does the Chrysler siren at close range alter perception?) I never knew, for example, that a sound could be so loud that it would make eyes water, sinuses ache or that you could see clothing take on a blurry appearance from rapid motion.

At this point, it was time for me to continue on my journey back to New England. I am very grateful to Harry for sharing this with me. There is no doubt that this entire concept of collecting and using horns, whistles and sirens as hobby interests can take you on a truly exciting journey wherein you will meet some really fine and interesting people and see and experience many unusual things which remain beyond the reach of those whose interests are more conventional.