WRAL WeatherCenter Blog

The Siren's Song

Posted June 2, 2009

We've already seen a fair bit of severe weather this spring, and with more storms sure to follow, getting the word out when those storms pop up is very important.  It would stand to reason that officials would use any and all tools available to alert the public.  However, one recent transplant to the area noticed one of those tools has fallen silent.  Bill B. from Cary writes:

As the recent tornado threats become real here in the Triangle...why do communities not use the tornado sirens to warn citizens of approaching life-threatening weather? Living close to the Cary Crossroads area..I witnesses children still playing outside as your warnings were announced. (As you can imagine, moving here from the Midwest was quite a shock to see this safety measure not utilized in many communities.) Thank you.

Growing up near Winston-Salem, about a two-hour drive to the west, I remember hearing the civil defense siren tests every week.  Sirens were also commonplace during my days in Texas.  Most communities had some form of outdoor warning sirens there, and the wailing of those sirens was common whenever severe weather threatened. 

Around here, though, sirens are few and far between, and how they're used varies from place to place.  Some very small installations -- the new alert sirens on the NC State and UNC campuses, for example -- do exist.  There is also a small network of sirens around the Shearon-Harris Nuclear plant, as well.  The campus alert sirens do sound for severe weather, but the Shearon-Harris ones do not.

That is one of the most significant issues surrounding these sirens.  Since local communities are usually responsible for operating (and in most cases, paying for and maintaining them), the policies governing how they're used can vary widely from one town to the next.  During a recent workshop in Kansas City, how the sirens were used was a hot topic, especially since nearly every community in the KC area has a different idea for how they're used. 

For example, some communities only sound the sirens for tornado warnings where a touchdown has been confirmed by a spotter.  Others sound them for all severe thunderstorm, tornado, and high wind warnings, as well as at various times every day, regardless of weather.  Someone commuting from one side of the Kansas City metro area to the other might be used to not hearing them except when the weather is turning wicked and hear one of the regular "lunch hour" or "quittin' time" sirens and not know what's going on.  At its core, this is a public education issue, but it's a very sticky one without any easy answers.

There are other issues, too:

  • In spite of the sirens being "outdoor warning sirens", many people believe the sirens will be enough to wake them up from a deep sleep, at night, and inside their homes.  This is a dangerous misconception, since that will only be true for someone who lives with the siren right outside their doors!
  • Along the same line, outdoor warning sirens were intended, in large part, to notify those who work outdoors and away from other means to get the warning information.  Our culture has shifted such that the vast majority of us spend a lot more time indoors, and regardless, most of us have a cell phone, pager, or other device that could be configured to get the warnings.
  • Some sirens have different sounds for different threats, meaning the public must be educated as to what these cryptic sounds mean.  ("I heard three long beeps and a short beep -- does that mean a tornado is coming or that there is some kind of nuclear emergency?"  It's an extreme example, but think about it; what you would do in one of those situations is the exact opposite of what you would do for the other.")
  • Naturally, the sirens, must be maintained, which costs time and money -- neither of which local governments have in abundance.  They can also fail (power is knocked out by a tornado and the battery backup fails, for example), leaving people who were counting on that alert hanging out to dry.

In spite of these issues, the folks in Kansas City were almost to a one very passionate about having them, and I've found that to be true for people from the Plains or Midwest who move to other parts of the country. My personal opinion is that their time has come and gone for all but a select few places -- university campuses being perhaps the ideal example of where they can work. Think about it: they're small areas with centralized "government" and formal policies governing their use. Multiple avenues exist to educate faculty, staff, and students about them, and they're used in conjunction with other formal notification schemes, not as a standalone method for getting information out.

What do you think?  Should we have warning sirens here, and if so, what kind of events should we sound them for?  If not, is there another alternative that would reach as many (or more!) people, be cost effective, and perhaps require less public education beforehand?


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  • rjweis00 Jun 5, 2009

    Sound decays with distance according to the inverse square law of -6 dB/doubling the distance, plus a frequency dependent loss known as atmospheric absorption, in which sounds lose x dB/1000 feet at a given frequency. This loss is proportional to the frequency. A loss of 1 dB/1000 feet is typical for a frequency of 500 Hz. The frequency spectrum of most current warning sirens contain frequencies well above this. An atmospheric absorption loss of a typical warning siren today is over 2 dB/1000 feet. It does NOT decay at some arbitrary figure, such as 10 dB/doubling the distance, that is found in most siren literature today.

    Airborne Sound Transmission Loss

    The above website shows that it is much harder to stop lower frequencies than higher frequencies, as the transmission loss of common building materials increases with frequency. Regardless of the building material, the general trend is that it becomes more effective in blocking th

  • planter Jun 3, 2009

    Your weather alert system is the best method I have seen and it is very effective. Receiving a phone call when weather threatens your area probably has the capability to reach the majority of the population. The real key is public awareness of the potential dangers of severe weather. Everyone has the responsibility to protect themselves.

  • gymjudge Jun 3, 2009

    Having grown up in 2 states in the Midwest, I was totally shocked to be working in a school without a Plectron (weather alert device used widely) I asked them how they are notified if there was a tornado and the reply was: "The central office calls us". (1977) Now thanks to computers and the internet, there are much better ways but I still feel more comfortable when I am back in the Midwest. I like their system of sirens and organized, trained weather spotters (my dad is one. Differences in in our geography makes the spotters less helpful but I miss the information from the sirens!