(AP): - Children in deep sleep awoke to recordings of their mothers' voices calling them by name and ordering them out of their bedrooms even if they slept through the beeping sound a smoke alarm makes, according to a small study.

The study reaffirms previous research that shows what works for adults does not always work for children, said Dr Gary Smith, one of the co-authors.

"Clearly, the strategy that has been tried and true and used for years ... fails miserably for children," said Smith, director of the Centre for Injury Research and Policy at Columbus Children's Hospital.

The study of 24 children ages 6 to 12 found that 23 awoke to the recorded voice of their mother saying "(Child's first name)! (Child's first name)! Wake up! Get out of bed! Leave the room!" Fourteen of the children also awoke to the traditional tone alarm. One child did not wake up to either.

Those who responded to both alarms woke up faster to the voice, at a median time of 20 seconds compared with three minutes for the tone alarm, according to the study by Columbus Children's Hospital researchers being released on Monday in Pediatrics.

Both alarms were created using a large speaker and sounds measuring 100 decibels, about four times louder than levels used in standard home alarms, Smith said.

The next step, he said, is to determine why children responded to the voice alarm differently, whether they were responding to their names, their mothers' voices or the frequency at which the sound was delivered, which was lower than the frequency of a beeping alarm.