At approximately what distance will a single artillery round set off a car alarm?

SPC Elijah J. Henry, MBA — Wed, 17 Aug 2022 07:38:23 -0400

I realize the answer will vary based on a lot of factors, and I realize there are many kinds of artillery rounds, but I'm looking for a ballpark figure.

Response by SSG Carlos Madden made Aug 17 at 2022 7:55 AM

SSG Carlos Madden — Wed, 17 Aug 2022 07:55:43 -0400

I'm no artillery expert but I'd imagine it would depend on the type of round, weapons system it was fired from, and the surface it impacts. For example, a round fired from an M119 from a short distance into sand would likely be very different than an XM1113 round fired from an M109 at long range into a concrete structure.

Response by CSM Darieus ZaGara made Aug 17 at 2022 8:18 AM

CSM Darieus ZaGara — Wed, 17 Aug 2022 08:18:24 -0400

A car would not be that close to an artillery piece. Not a wise move.

Response by CSM William Everroad made Aug 17 at 2022 12:07 PM

CSM William Everroad — Wed, 17 Aug 2022 12:07:35 -0400

Most car alarms pick up low frequency "vibrations" in their shock sensors. They operate in a range from 10 to 200 Hz. Since mortar explosions can send a sound shockwave up to 400 Hz, it can set off the shock sensor. The consideration is the "noise" traveling in a pressure wave. At this level you get the highest amount of sound pressure in terms of decibel rating. Even at 400 Hz, the receiver has to detect the sound wave, so the db (sound pressure level) level matters, thats why a very loud high frequency noise won't do it. Additionally, blast overpressure is the result of displaced air, but that will set off the tilt sensor in the car alarm from the physical movement of the car. The sound pressure level drops off over time: an 81mm exceeds 130 db out to 5000m, but the pressure level drops significantly (can hear it, but not feel it; still damages hearing though).

Napkin math suggests that @ 100m you stand a good chance of setting off the alarm with decreasing reliability (depending on surface material at the impact site, humidity, and temperature) as you move out to 300m.

Response by SFC Kelly Fuerhoff made Aug 17 at 2022 6:02 PM

SFC Kelly Fuerhoff — Wed, 17 Aug 2022 18:02:42 -0400

I don't know but about 4-5 years ago when I was in Nebraska, someone set off a very large firework in our apartment complex area that set off several car alarms. It sounded like it came just from the other side of my apartment building lol. I don't know what the firework was but it sounded like an artillery boom...and at least 3-4 car alarms went off in the parking lot lol.

Response by MSG Douglas Wilson made Sep 1 at 2022 7:12 PM

MSG Douglas Wilson — Thu, 01 Sep 2022 19:12:01 -0400

Lived about twenty miles from impact range when low ceiling cloud cover car alarms would go off

Response by Cpl Robert Sutton made Sep 22 at 2022 1:18 AM

Cpl Robert Sutton — Thu, 22 Sep 2022 01:18:51 -0400

15 feet