Neuroscience For Kids

Alarming News

Voice alarms more likely to wake up kids
November 15, 2006

When was the last time you checked your home smoke alarm? Does it work? Does it have a good battery? Is it located in the best place of your house? A properly installed smoke alarm can save your life in the event of a fire.

But smoke alarms do not always awaken everyone and being asleep during a fire increases the risk of death. Children are especially difficult to wake up from the sound of a traditional smoke alarm. A new study suggests a more effective alarm for kids: a mother's voice!

Alarming Experimental Set Up

Researchers tested the ability of a traditional tone smoke alarm and the sound of a mother's voice to wake up children from stage 4 sleep. The mothers of 24 children (6-12 years old) recorded a voice alarm with their child's first name such as "Sam! Sam! Wake up! Get out of bed! Leave the room!" Both the traditional tone alarm and the voice alarm were set to play at 100 decibels.

The children slept in a sleep laboratory with electrodes attached to their heads to record brain activity, muscle activity and eye movements. Once the children were asleep and had been in the first period of stage 4 sleep for five minutes, one of the alarms went off. The time it took the children to wake up and get out of the room (an escape) was recorded. The kids were then brought back to bed and allowed to fall asleep again. When the kids entered stage 4 sleep again, the other alarm was sounded and the time to wake up and escape were recorded.

Alarming Results

Of the 24 children:

• 23 (96%) children woke up to the parent voice alarm.
• 14 (58%) children woke up to the tone alarm.
• 1 (4%) child did not wake up to either alarm.
• 9 (38%) children woke up to the parent voice alarm, but not the tone alarm.
• 0 (0%) children woke up to the tone alarm, but not the voice alarm.

The voice alarm woke up the children in an average (median) of 20 seconds and 20 of these children escaped within 5 minutes. The children were awakened by the tone alarm in an average of 180 seconds and only 9 of them escaped within 5 minutes.

Older kids were more likely to wake up to the tone alarm. Only 2 of 10 children younger than 9 years were awakened by the tone alarm, but 12 of 14 children older than 9 years woke up to the tone alarm

Alarming Questions

This experiment demonstrates that voice alarms are more effective than tone alarms in waking up children from stage 4 sleep. What makes the voice alarm more effective is still unknown. It may be that the sound of the child's name or the familiar sound of the mother's voice is the important characteristic of the alarm. Alternatively, the frequency of a human voice may be the important factor. Future experiments that compare a mother's voice to that of an actor's may reveal some answers.

Did you know?

In the United States in 2005: 3,675 people were killed as the result of fire. 17,925 people were injured as the result of fire. 115 firefighters were killed while on duty. Fire killed more people than all natural disasters combined. 83% of all fire deaths occurred in residences. (Source: U.S. Fire Administration)

Reference and more information:

• Smith, G.A., Splaingard, M., Hayes, J.R. and Xiang, H., Comparison of a personalized parent voice smoke alarm with a conventional residential tone smoke alarm for awakening children. Pediatrics, 118:1623-1632, 2006.
• Sleep - Neuroscience for Kids
• Sleep Experiments - Neuroscience for Kids

Copyright © 1996-2006, Eric H. Chudler, University of Washington