TORONTO -- Anger at cellphone Amber Alerts that rouse people from their sleep is misplaced and shows the need for more public education, observers said on Tuesday.

People need to understand that the emergency alerts are only issued when police need help in finding a child they believe is in grave peril -- usually the result of an abduction, they said.

Ken McBey, a professor at York University who specializes in social and behavioural elements in emergencies, said those who light up 911 to complain about the alerts are being "incredibly selfish."

"It's just one of those trade-offs: It's a matter of balancing off individual interests for what's best for society," McBey said. "Part of this is actually shaping perceptions. To a certain degree, emergency authorities have a sales job to do. They haven't done it as well as they could have."

The latest situation arose in the early hours on Tuesday, when police in the area of Sudbury, Ont., issued an Amber Alert, sending a cacophonous, piercing tone to cellphones along with details of a missing three-year-old boy and the circumstances of his alleged abduction.

As in the past, some recipients objecting to being disturbed called emergency services to vent their anger. That in turn prompted a plea from police in Toronto, where the missing child was found safe, as well as the city's mayor to warn against making such calls to 911 as they could delay response to a real threat.

"Being woken up by an Amber Alert is not an emergency," Toronto Mayor John Tory pointed out in a tweet.

Amber Alerts used to be broadcast via mainstream media, missing people who weren't watching television or listening to the radio. Social media helped, but for about a year now, the technology has allowed alerts to be sent to almost all cellphones within a certain geographic area.

Karen Chymy, with the Canadian Centre for Child Protection in Winnipeg, said she's heard complaints from people upset at the disruption. At the same time, she said, far more people understand the importance and are comfortable with the intrusion.

"It's new, so people are learning about that system and how it's being used," Chymy said. "If it were our own child, we'd want the public to be aware."

Those who seek to help children say Canadians are fortunate the technology allows alerts to reach so many people so quickly -- even those who can't help at that moment. While they say they understand the annoyance some might feel at being roused from sleep, they note an alert might still be active when those people are up and out.

"This alert is working. It's finding children, it's keeping them safe," Amanda Pick, CEO of Missing Children Society of Canada, said from Calgary. "That should be our answer every day: We will stand together to receive that information and protect children."

While individual emergency services make the call on issuing cellphone alerts, avoiding them is generally not possible. Greg Burch with the Canadian Wireless Telecommunications Association said the approach is deliberate and mandated by the federal regulator, the Canadian Radio-television and Telecommunications Commission.

"Given the importance of warning Canadians of imminent threats to the safety of life and property, the CRTC requires wireless service providers to distribute alerts on all compatible wireless devices connected to an LTE network in the target area," Burch said. "Therefore, it is not possible to opt out of receiving the alerts."

A spokeswoman said the CRTC is not responsible for the distribution or content of alerts. However, Patricia Valladao said the commission continues to discuss concerns heard from the public and others to encourage adoption of measures to improve the system.

McBey, of York University, said technology is continuing to evolve and a more refined system of alerts will likely develop. In the interim, he said, people should remember that much of what crosses their smartphones every day is trivial compared with an alert.

"An Amber Alert is a pretty important thing for society. You've got lives that are in danger," he said. "It isn't to wake you up and to irritate you."