When the cockpit recorder transcript from Air France Flight 447 was leaked to the public in 2011, many startling details emerged. The plane, which crashed into the Atlantic Ocean on June 1, 2009, killing all 228 people on board, had been under the control of pilots who were communicating poorly and not realizing one another’s mistakes. The plane’s speed slowed to dangerous levels, activating the stall alarm—the one, in the words of Popular Mechanics, “designed to be impossible to ignore.” It blared the word “Stall!” 75 times.
Everyone present ignored it. Within four minutes, the plane had hit the water.
Alarm sounds are engineered to elicit particular responses in humans. And yet, sometimes, humans choose not to respond, having decided that the situation is not urgent enough or that the sound is a false alarm. Audio alarm designers seek to avoid this by designing sounds that have an intuitive meaning and precisely reflect the level of urgency. But what makes an “awooga” sound more or less urgent than a “ding”? And how do you create an alarm noise that’s annoying enough to get someone’s attention, but not so annoying that said person disables the alarm?
Auditory alarm designers like Carryl Baldwin face these questions regularly. Baldwin, a human factors psychologist, constructs sounds in a lab, tests those sounds on human subjects to see if they are communicating the intended meaning, and ensures they are appropriate for use as alarms in household, aviation, medical, and automotive settings.
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