By Kathi Mestayer

Warning sounds and emergency noises are designed to get our attention using sound. It is, after all, the only kind of signal that will effectively reach everyone in the vicinity—even if we’re out of visual range, facing the wrong way, in total darkness, or even asleep.

In the case of alarm sounds, a stress reaction, or mild panic, is exactly what’s needed. The purpose is to get people’s attention, without causing them to veer off the road, or go back to checking their email.

Studies of individuals’ responses show that alert sounds should have the following properties:

1. Sufficient volume (about 15 dBA above the background noise; dBA refers to the volume as perceived by the human ear)

2. A wide range of frequencies

3. Rapidly rising frequency

4. Fast cycle time (rapidly repeating sounds with short intervals between them)

A hard-of-hearing friend was surprised to find out that he couldn’t hear his smoke alarm. He and his wife were standing under it, when he pushed the “test” button. As she bolted from the room to escape the noise, he just stood there with a puzzled look on his face. Didn’t hear a thing—his hearing loss just happened to drop out completely at that frequency. So, they got a special smoke alarm with a broad range of (lower) pitches.

One of the most mind-bending siren sounds I’ve heard online is that used by the city of Chicago. The website characterizes the tornado sirens as sounding “like a dying whale from hell.” Oh, right, I thought—they can’t be that bizarre, can they? Oh, yes, they can—the eerie whine pulsates, changes volume quickly, and climbs up—and down—and up again—over a broad frequency spectrum. But, after all, they are trying to get us quit what we’re doing, and prepare for a tornado. You’d have a really hard time ignoring it.

This is only a test…

The most-recognized alarm sound is the federal Emergency Alert System, which became official in 1997, and is used primarily for weather alerts. It’s the one you hear on the radio, with loud, corrosive klaxon blasts followed by the “this is only a test of the Emergency Alert System” script. The first sounds, called the “header,” are designed to get our attention and make us rush to the radio to turn the volume down. The header is followed by a continuous-tone “attention signal” at two frequencies, followed by the script (if it’s a test) or the emergency information (if it’s real). The message ends with a three-burst pattern of the header.  

FCC rules prohibit unauthorized use of the Emergency Alert System sounds (or anything closely resembling them), but…    

Testing, testing: zombie apocalypse!

A well-defined and thought-out system like that is just begging to be hacked, right? Well, some folks managed to do just that at a TV station in Montana to broadcast a warning about a zombie apocalypse. They were just trying to warn us, right? Here’s a segment from the Associated Press coverage of the event:

“The Montana Television Network says hackers broke into the Emergency Alert System of Great Falls affiliate KRTV and its CW station Monday. KRTV says on its website the hackers broadcast that ‘dead bodies are rising from their graves’ in several Montana counties. The alert claimed the bodies were ‘attacking the living’ and warned people not to ‘approach or apprehend these bodies as they are extremely dangerous.’”

They were just trying to help… if there had, in fact, been a zombie attack, we would be thanking them profusely, right?

My friend Steve worked at an experimental physics facility in Japan, and told me that their “crane alarm” was extremely effective—it sounded like a woman screaming bloody murder. Not periodic, just a continuous scream that was impossible (for him, anyway) to ignore. It made him nervous, got the adrenaline pumping, and he never got used to it.

Steve also observed the “alarm tune-out” phenomenon. When the earthquake warning siren sounded, he ran the protocol—turning off equipment, securing gas bottles, and finally ducking under a table. Nobody else seemed to notice the alarm, except for an occasional, curious colleague peeking under the table at him. “I think they were used to earthquakes,” he says.

Staff writer Kathi Mestayer serves on advisory boards for the Virginia Department for the Deaf and Hard of Hearing and the Greater Richmond, Virginia, chapter of the Hearing Loss Association of America. This is adapted from her reader-sponsored work on Beacon Reader.