Weird claim about Sentry 10V's hearing range... please help me dissect this

[archizackture]

This keeps coming to my mind, and it bewilders me every time, so I decided to finally ask about it.
Several years ago, I had a conversation with some firefighters who claimed they could hear the Sentry 10V in Berkeley Springs, West Virginia (it's my profile picture) from their fishing spot on the Potomac River. I didn't say anything about it then, but I thought it was ridiculous. Still, the possibility makes me wonder.

Here's the details of the situation:
- Any given point along the Potomac around here is 15 or 16 miles away from the 10V "as the crow flies." There's one spot that's only 11 miles away, but it's on the other side of two very tall ridges.
- There are no highways, factories, town centers, or other sources of noise anywhere in that 15-16 mile span
- The 10V is on a ridge at an elevation just over 1000 feet, higher than any other land over that 15-16 mile span, but not as high as the two ridges in the way of the 11-mile span.
- The firefighters were from a different fire department
- There's a different siren, a Sterling K-5 that sounds nothing like the 10V, close to the river on the other side
- We didn't discuss the 10V by name; I didn't know about siren models back then; we named it by the VFD where it's located, South Morgan VFD.

I know there's a method of calculating sound fade over distance, but I forget what it is. How would I take 115 dBc and calculate its intensity at 15 miles? Does it matter that the 460hz tone carries well over distance, better than higher tones? Can we be sure whether or not we've debunked the firefighters' claim?

I used to live 3 miles (again, as the crow flies) from the 10V and it could penetrate the house easily (here's my own recording), but 15 miles?? Golly!

[JasonC]

Range varies wildly with the weather. I have a 3v8 fire siren a mile from my house. Some days it sounds like its right across the street, others you literally cannot hear it going off

[DJ2226]

The weather will do it, especially wind. The wind will blow the sound. I think omnidirectional sirens are more subject to this because of the fact that they distribute their sound evenly. Rotating sirens throw all of their sound in one direction which makes it easier to counter and fight the wind. it will mess with the intensity of the SPL. I live about a half mile away from a 2810. Most times I can hear it from inside, but with a strong enough sustained wind blowing the sound in the direction of the siren it sounds way quieter. Whelen's and Sentry's omnidirectional sirens can fight it to a large extent, but the sound will definitely take on the effect of a wind vane. I've had an odd experience recording a 2805 from a distance where the wind blew the sound away from the siren. It seemed so weird and actually a little trippy, because the sound itself didn't seem like it was coming from the siren. It was like the siren was to the left of its physical location.

[archizackture]

This is all very interesting, thanks for your replies! I've certainly experienced the effects of weather on sirens, as between the 10V and the Sterling M-10 a quarter mile from where I live now, and a Model 5 near my college campus, all sounding for local emergency calls, I've been hearing sirens on a daily basis for just over 13 years. Even still, the idea that environmental and terrain conditions could multiply a siren's audible range by around FOUR TIMES has been gripping at my curiosity for years. It just seems totally absurd. But then again, as I mentioned before, there's no major sources of noise inbetween and the terrain gives the sound a pretty clear shot over that distance.

I do know some people who live around 5 miles and 8 miles away from the 10V. I suppose I could ask them if they've ever heard it. The farthest distance I've personally heard it from, very faintly, was just over 4 miles at a house near Cacapon Resort State Park.

[Stormsetter4]

I highly, HIGHLY doubt the siren they heard was that 10V. If it were something along the lines of a Thunderbolt I might believe it, but my past experience with the 10V has not been very impressive. I had one you couldn't hear very well a half mile away. All that was in the way were 5 or 6 trees and some houses.

[archizackture]

I highly, HIGHLY doubt the siren they heard was that 10V. If it were something along the lines of a Thunderbolt I might believe it, but my past experience with the 10V has not been very impressive. I had one you couldn't hear very well a half mile away. All that was in the way were 5 or 6 trees and some houses.

I'm thinking they were most likely hearing the Sterling K-5 in Hancock, Maryland since it's very close to the river where they fish. There's no other sirens within 5 or 6 miles of there besides the Sterling M-10 in downtown Berkeley Springs, which it MAYBE could be but I've only ever been able to hear that siren from 2 miles max. The M-10 is 8/16 port and the lower tone is about 432hz (I measured) so it's possible it could be mistaken for a 10V from a distance, but a K-5 doesn't sound like either of those at all. But of course, I wouldn't necessarily expect the guys I chatted with to identify pitch as easily as I, a musician, can.

I do remember asking if they were sure it was the siren at South Morgan Volunteer Fire Department, and they said yes, they were sure it was. I don't know what background they had with SMVFD, but they were convinced that they were hearing its 10V.

That's too bad about your experience with the 10V, but it's completely different from mine. The one here in Berkeley Springs (which has a relatively volatile and fragmented terrain form and plenty of forest) at South Morgan VFD has a solid 4-mile radius from my experience. And it's one of the originals, installed in the 1980s when the station was built.