The electromechanical siren was invented around the turn of the twentieth century and local governments bought them in spades during the Cold War. Last I counted, Delaware County has more than thirty outdoor warning sirens, and Muncie’s trio of elderly Federal Signal Thunderbolt 1000s are my favorites.

When I worked nights, nothing was better than being startled awake by the apocalypse every Friday morning at eleven when those outdoor warning sirens were tested! I had Federal Signal Corporation to thank for my wakeup call since that company developed the Thunderbolt-1000 from 1949 to 1952 for civil defense purposes to alert communities to an impending Soviet attack. Nearly everywhere I’ve lived in the post-industrial midwest is said to have been on Khrushchev’s hit list at one time or another, so six Thunderbolts arrived in Muncie on January 9, 1958, at the order of Marshall Sipe, Delaware County’s Director of Civil Defense. The first wave of Muncie sirens were installed at the following places and promised a circular mile of coverage:

• Riley Elementary School
• Roosevelt Elementary School
• Franklin Middle School
• Covalt Dairy
• Broderick Company
• Ball Stores

The Thunderbolt at Ball Stores was the last siren purchased and was installed in March of that year¹. The city’s Thunderbolts were first tested at 11:00 a.m. on Monday, March 24, 1958. Although the siren at Franklin failed to start, the rest were fully functional². Soon, smaller towns got in the game too, by hooking their old fire call sirens -often old Darley models or smaller Federal Signal sirens with two or five-horsepower motors- up to their county emergency systems.

Although Federal Signal’s Model 2 was introduced in 1907, the Thunderbolt was the world’s first supercharged siren when it appeared more than forty years later. Hearing one, even during a scheduled test, is terrifying thanks to their unique wind-up and throaty tone. Here’s how they work, or should have, in the case of the Thunderbolt at Franklin Middle School: the sirens were activated by a phone signal from the police radio station at 1201 North Broadway Street in Muncie³. Once a Thunderbolt got word to start screaming, three assemblies -a blower, a chopper, and a rotator- began moving.

The blower, or supercharger, forced air up a pipe towards the chopper, which consisted of a high-speed axial fan called a rotor within a stationary component called a stator. The spinning rotor opened a series of integrated holes called ports, which caused air from the blower to project into the big trumpet at the end, technically called an exponential horn. The tone that came out varied based on how fast the rotor was spinning and the number of ports. A separate assembly allowed the horn to spin in a circle so people from all directions could hear the siren.

A separate assembly allowed the horn to spin in a circle so people from all directions could hear the siren. Thunderbolt 1000s featured the same universal motor and single-tone 5-port chopper motor that the venerable Model 2 utilized, but the sirens were twenty-five decibels louder than their older contemporaries thanks to the supercharged air flowing through them.

At full speed ahead, a Thunderbolt can generate sound across an overall frequency range of about 128-700Hz. They’re powerful: single-tone units can reach intensities of 127dB from 100 feet away! Thunderbolts typically produce two tones, a steady signal called “alert,” and “attack,” a wail that varies steadily in pitch. Thunderbolt 1000 models produced a single tone, while Thunderbolt 1000Ts, like the one at Southview Elementary School, sounded off with a dual tone signal. Fortunately, I’ve never been in enough of an emergency to hear wail or fast wail cycles through a mechanical siren, but I’ve been close!

In 1973, the Thunderbolt atop Ball Stores was removed to provide room for new air conditioners installed during a remodeling project. Although the initial plan was to reinstall the siren on Muncie’s downtown water tower⁴, it was eventually relocated to Storer Middle School on the city’s northwest side⁵. That year, a plan was drafted to begin using the sirens for tornado warnings after the 1974 Super Outbreak destroyed the White County Courthouse in Monticello⁶. I believe that the siren on top of the Delaware County Building, an ACA Banshee 110, was added to the county’s roster around that time.

After it was relocated, Storer’s Thunderbolt proved problematic: in the early morning hours of Friday, May 2, 1986, residents were awakened with a start when it randomly started blaring for fifty-five minutes beginning at 1:30 in the morning⁶. The following year, the siren failed to activate during a statewide tornado drill⁷. By 1995, sirens in Muncie were located at Southview Elementary School, St. Lawrence Elementary (the former Franklin Middle School), Northside Middle School, Riley Elementary, and the former Broderick Company plant⁸.

Over time, Thunderbolt sirens have largely been phased out of existence as they aged. Today, three remain in Delaware County. Only one is in its original location, the former Riley Elementary School, although it no longer rotates. A fourth was at North View Elementary School as recently as 2013. It can be seen in the Google Street View image above but has since been replaced. In 2023, most of Delaware County’s sirens are boring Federal Signal SRN-2001s, which succeeded the more complex Thunderbolt series in 1988. Today, SRN-2001s are by far the most common outdoor warning sirens in Indiana.

Nearly two-thirds of the outdoor warning in Delaware County are modern Federal Signal SRN-2001s. Thanks to the Thunderbolts, though, if you live in or around Thomas Park/Avondale, Carlton-Ludingwood, and Cowing Park, your Friday experience differs from 92% of your companions in the county. You’re hearing some history when one of Muncie’s old Thunderbolts revs up! I wish I could since I live a mere 1,600 feet from a modern SRN-2001.

Actually, I can: despite my close proximity to an SRN-2001, Thunderbolts are so loud that I can hear one clearly every Friday even though it’s more than a mile and a half away from my house. It drowns out two 2001s closer to me and a third that’s equidistant. Part of that’s due to the siren’s unique tone.

I recorded the video above from my balcony in March 2021. You can hear the SRN-2001 nearby; three others; the Thunderbolt at five seconds in; and two of Ball State’s electronic Whelen WPS-4004s near the end of the clip. I may have picked up the SRN-2001 at Beech Grove Cemetery, but it wasn’t obvious when I analyzed the audio.

I realized that I didn’t have a video of a Thunderbolt in action as I finished this post, so I took a half day at work yesterday and high-tailed it to the Gresham Center to nab some footage of the siren there. I parked about a hundred feet southwest of the aging siren and braced my phone on the rim of my open sunroof as it sprung into action. As you can see in the video, I was unprepared for the siren’s 127 decibels: the shockwave made my phone shake! I worked in the Gresham Center for about a month in 2014 and had to pray I wasn’t on the phone during a Friday test!

According to an exhaustive Google Map produced by Spencer Harman with help from Tyler Noie, Brandon Mendel, Ian Tate, Matt Hacker, and others, twenty-one of Federal Signal’s Thunderbolt 1000 sirens still exist across Indiana in cities like Auburn, Elkhart, Gary, New Castle, and Muncie, and others. That means Muncie operates 14% of these supercharged relics across the Hoosier State, and I think that’s great. I love to see history in action! Thunderbolts didn’t just operate in Indiana, of course. Just east of Muncie, Illinois, I spied an old Thunderbolt next to the penthouse of the tallest building in Danville a couple years ago. You can see it if you look closely, but I’ve read that the siren hasn’t operated since 2008¹⁰. 

Someone asked me why I’m so drawn to outdoor warning sirens. I don’t know! I’ve always had a thing for hidden infrastructure, which has often informed my research and writing. I’ve also occasionally been labeled an obnoxious noisemaker myself, so maybe that gives the best answer. At any rate, Delaware County, and Muncie in particular, is home to a shrinking breed of vintage sirens. They’re historic, and I, for one, am glad that they disrupt our schedule with their apocalyptic intrusions.

Sources Cited
1 Downtown Siren Last in CD Link (1958, March 17). The Muncie Evening Press. p. 1.
2 New CD sirens Will Be Tested Monday Morning (1958, March 21). The Muncie Star. p. 6.
3 Sirens’ Wails Are Check on CD Warning (1958, March 24). The Muncie Evening Press. p. 1.
4 Collier, W. (1974, June 7). Civil defense siren sounds in city again. The Muncie Evening Press. p. 1.
5 Canan, J. (1998, May 24). 25 years ago. The Muncie Star Press. p. 30.Canan, J. (1998, May 24). 25 years ago. The Muncie Star Press. p. 30.
6 (See footnote 4).
7 Siren Malfunction Causes Sleep Loss (1986, May 3). The Muncie Star. p. 4.
8 Annual Tornado Drill Proceeds Fairly Smooth (1987, March 11). The Muncie Star. p. 12.
9 Hale, J. (1995, March 16). No siren, but no worry. The Muncie Star. p. 1.
10 Bailey, Jennifer. “City to review warning system” The Commercial-News [Danville].  June 19, 2008. Web. Retrieved 3/17/21.