Why can't firefighters hear the alarm?

Firefighters are equipped with emergency alarms with quite large sound intensity. However, their colleagues participating in fire fighting often do not hear this alarm. So what is the reason?

Researchers from the University of Texas are trying to find answers to the strange phenomenon. Firefighters often carry personal alarms. In an emergency or lack of oxygen this alarm device is activated.

If the firefighter does not move, in 5 seconds it will play a loud sound, about 95 decibels (a unit of sound intensity) to send a warning signal to other firefighters who are also taking care of it. Fire. It was a sound of great intensity, but in the burning building, their colleagues often couldn't hear.

Photo: fireathletebootcamp.com

There is a simple explanation, with the chaos in the burning building, due to outside noises, dark weather or suffocating sensations and firefighters often hugging their hats. That is something everyone can see. But there is another important reason.

Sound velocity in different hot and cold air. In burning buildings there are very hot air zones intermingled with cold air areas caused by water and other fire extinguishing substances.

Heterogeneous environment causes the path of sound waves to change direction and continuously reflect. Firefighters feel like they hear sounds coming from many different locations. Therefore, they could not determine the location of the sound emitting a warning from a colleague.

Currently US scientists are studying a new warning device that can change the pitch (frequency) or tone of warning sounds to overcome the disadvantages of existing devices.