We deal with loud environments often: concerts, construction sites, etc. It can be physically painful if the ambient noise is loud enough. Because of this, it makes sense that many people avoid such settings in an attempt to avoid hearing problems in the future.
If this is true, then why are fire alarms so loud?
Fire alarms are LOUD
NFPA 72 outlines the requirements for fire alarm notification appliances, which take two primary forms: audible and visible.
- Horns and sirens provide the audible alert, sounding off at 65 to 120 decibels (dB) when standing 10 feet from the device.
- Strobe lights provide the visible alert, flashing once per second at 15 to 1,000 candelas, depending on the setting.
It’s well known that repeated exposure to loud noises can be damaging to your hearing. The National Institute on Deafness and Other Communication Disorders (NIDCD) states that 85 dB and higher is the danger zone for hearing loss.
Here are some comparative noise examples to help you understand the loudness of different decibels:
- Indoor conversation: 50 dB
- Chatter in a restaurant: 60 dB
- Vacuum cleaner: 70 dB
- Garbage disposal or food blender: 80 to 90 dB
- Power lawn mower or motorcycle engine: 100 dB
- Thunderclap: 120 dB
- Jet take-off from 25 meters away: 150 dB (eardrums may rupture if exposed to this volume without ear protection)
So… Why are some fire alarms louder than others?
The goal of a fire alarm is to make sure everyone in the building knows to evacuate. That’s why the NFPA requires fire alarm horns and sirens to sound louder than ambient noises.
The precise requirement is 15 dB above the average noise level or 5 dB above the maximum ambient sound, whichever is greater. This means it may be appropriate to program fire alarm horns to 75 dB for a restaurant or office setting, but an industrial facility with loud equipment may need to sound off closer to the maximum 120 dB level to ensure the sound stands out from other ambient noises.
The high volume requirement for fire alarms accounts for the fact that distance from the horn decreases its perceived volume, and building materials absorb noise, especially if the doors are closed between rooms. Due to these factors, the decibel level must be high at the source to ensure the sound travels to every corner of the building.
Can I protect my ears from the noise of a fire alarm?
When you hear the shrill noise of a fire alarm, your first instinct is to cover your ears. This is actually an effective way to defend against hearing loss while you walk calmly toward the exit and make your way out of the building.
More importantly, however, is to create a fire evacuation plan and hold fire drills regularly. This way, everyone is confident about what steps to take and where to evacuate in case of an emergency. By planning ahead, you can limit confusion and reduce the time you’re exposed to loud volumes.