How Does a Glass Break Detector Work?

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Door and window sensors sound an alarm when someone opens a door or window to your home. But if a burglar were to break into your home by smashing a window—instead of forcing it open—the window sensor wouldn’t trigger.

Glass break detectors complement door and window sensors by monitoring sound or vibration. When they detect the frequency or shock waves associated with glass shattering, they sound an alarm. These devices are great additions to a home security system because they can remain armed all the time, unlike motion detectors, which must be turned off when you or your family are at home.

Here’s a closer look at the technology that makes these window break alarms work.

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The science behind glass break sensors

There are two main types of glass break alarms. The first type features shock sensors, which monitor for the vibrations of breaking glass. These are generally mounted directly on the windows they’re monitoring. It’s worth noting that these types of detectors can sometimes set off false alarms, as a door slamming could mimic the same vibrations of glass breaking.

If you’re worried about false alarms, you can opt for a glass break detector that relies on acoustic sensors instead. A small microphone listens for the specific frequencies of breaking glass. If a burglar were to break through a window, the detector would pick up on the high-pitched shattering sound to trip the alarm.

Where to install glass break sensors

Glass break detectors are ideal to use in rooms with large windows and sliding doors. The detector is a small device you attach on or near your windows. Like a motion sensor, the range is limited, so you’ll likely want multiple glass break detectors for your home.

Adjusting device sensitivity

When considering glass break detectors, many people worry about triggering false alarms if they accidentally break a glass plate or are watching an action movie. Potential false alarms are why you should test and adjust sensitivity levels when you first install your glass break detectors.

The testing process will differ depending on the detector you purchase, but most have a “test” button. When testing, you’ll clap your hands loudly near your windows. You can also play a video of glass sounds for greater accuracy.

Even after testing, there’s always the chance of a false alarm, so you may want to avoid placing glass break detectors in the kitchen or near your television, where other shattering noises are likely to be loudest.

Security brands that sell glass break sensors

Vibration-based glass break sensors are sold by these security brands:

Acoustic glass break sensors are more common among security brands: 

If your security company doesn't sell a glass break sensor, you're still in luck if you have an Amazon Echo—it has a built-in glass break sensor. Just turn on Alexa Guard.


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Celeste Tholen
Written by
Celeste Tholen
Celeste has dedicated her decade-long career to reporting and reviews that help people make well-informed decisions. She oversees editorial strategy and production for SafeWise, with a goal to help everyone find the information they need to make their homes and lives safer. Prior to SafeWise, she worked as an editor and reporter for KSL and Deseret News. She holds a Bachelor's degree in Journalism. In her free time, she volunteers at the local botanical garden and writers for the community newspaper.

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