Researchers believe smoke alarms may sound at too high a frequency to wake up children. They are testing a combination of a lower frequency and a female voice.

The project is led by Dave Coss, a fire investigator whose local area covers a house where six children died in a fire despite an alarm sounding. He’s now working with the University of Dundee.

The team has carried out a small study involving 34 children aged two to 13, each sleeping in their own homes. The researchers repeatedly sounded a standard smoke detector while they slept. The Guardian reports that overall the child slept through the alarm 80 percent of the time, with only two children waking up for every alarm.

In a surprising – if not necessarily statistically significant – finding, none of the 14 boys involved in the test woke up for any of the alarm soundings.

When the researchers repeated the experiment with a combination of a lower frequency and a spoken warning in a female voice, the overall “wake-up” rate rose from below 20 percent to 94 percent.

The researchers now want to repeat the study with 500 families to see if the findings hold up.