"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?

"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."
http://www.atlasobscura.com/articles/an-alarm-designer-on-how-to-annoy-people-in-the-most-effective-ways