On Friday, I was happily taking care of the dishes while half listening to a local radio station playing in the next room. Suddenly, over the sound of the running water, I heard the most unholy buzzing screech. I had to turn off the tap and run to the centre of my home to locate it and figure out what it was — Was it an air raid siren? The carbon monoxide detector?!
It took a good couple seconds for me to realize it was coming from my radio, and signaled an active Ontario-wide Amber Alert for a missing Welland girl. When the robot voice started giving the details, I relaxed — but then got to thinking about the effectiveness of the noise in getting me to drop everything and pay attention!
Turns out there are people out there whose job it is to design alarms: and not just to sound so freaky that you freeze and listen, but to make us understand the nature and urgency of the thing we’re being warned about. Plus, they have to circumvent our highly developed brains’ instincts to ignore or disable alarms we have determined to be false or too annoying — with sometimes fatal results. The design specifications are very precise:
“The faster an alarm goes, the more urgent it tends to sound. And in terms of pitch, alarms start high. Most adults can hear sounds between 20 Hz and 20,000 Hz— [designe Carryl] Baldwin uses 1,000 Hz as a base frequency, which is at the bottom of the range of human speech. Above 20,000 Hz, she says, an alarm ‘starts sounding not really urgent, but like a squeak.’
Harmonics are also important. To be perceived as urgent, an alarm needs to have two or more notes rather than being a pure tone, ‘otherwise it can sound almost angelic and soothing,’ says Baldwin. ‘It needs to be more complex and kind of harsh.’ An example of this harshness is the alarm sound that plays on TVs across the U.S. as part of the Emergency Alert System. The discordant noise is synonymous with impending doom.
The Emergency Alert System (have a listen here!) has similarities to the Ontario Amber Alert alarm. But I find the differences really point up what the listener’s reaction should be: to me, the former spells, well, “impending doom,” so I my instinct is to sit calmly and absorb all instructions; and the latter makes me want to get up and do something — like find a child.
The next big project facing alarm designers is forming an “alarm philosophy:” a way of organizing multiple alarms in an environment, so that the most important don’t get drowned out or ignored. Meanwhile, the Amber Alert for Layla Sabry of Welland is officially called off, but she is still missing: familiarize yourself with her case here. And keep your ears open for the next terrifying screech from your radio — someone worked hard to bring it to you!