How do glass-break sensors work?
Glass-break sensors often come as standard with car alarms sold in New Zealand. As the name suggests, they are designed to trigger the alarm when a window gets smashed to access the vehicle.
They are simply a microphone that detects high-pitch sound and, in turn trigger the alarm if (in theory) when a window is smashed. Normally they are installed in the front area of a vehicle, either below the dashboard or above it.
You won’t find glass-break sensors in factory installed car alarms. Most manufactures prefer ultrasonic sensors if adding anything other than just door, boot and (sometimes) bonnet protection.
Why glass-break sensors are not always effective
Whilst glass-break sensors often do the job well, they are not effective on some vehicles. They are not suitable for cars with:
- Pillarless windows
- Window tint film
Pillarless windows
Pillarless windows can be pulled open to access the cabin without smashing the glass or making the required sound to trigger the sensor.
Window tint film
After-market window tint film can stop glass break sensors from being effective.
Window tint film changes the acoustic sound of the glass breaking. The sensor is designed to detect a high-pitch shattering sound. The film muffles the sound of the glass breaking.
Glass-break sensors can also cause a false alarm if the sensitivity is set too high. The materials inside a car can cause a creaking sound as they expand and contract with a change of temperature, which can be enough to trigger an overly sensitive sensor.
Over sensitive glass-break sensors cause false alarms
Glass-break sensors are far less effective in large vehicles
Glass-break sensors are not very effective for large vehicles. Whilst they will detect a sound in the front of a vehicle, they are not as effective if the sound is further away. If you have a van alarm, then it is unlikely they a sensor installed at the front detect the rear window being smashes as the sound reduces over distance.
Don’t dial the sensitivity to full!
The temptation here is to turn up the sensitivity, but it is not a good idea. If the sensitivity is set too high you end up getting false alarms.
The materials inside a car can cause a creaking sound as expansion and contraction occurs with a change of temperature. This can be enough to trigger an overly sensitive sensor.
Tips to avoid getting a smashed window
Place security warning stickers on the most vulnerable windows
It’s often the smaller windows that get smashed on a vehicle.
It’s worth thinking like a car thief. Ask yourself which window would you break to be able to reach in and access the internal door handle?
Take the Toyota Aqua for example, the front quarter windows are the most common to ones to smash.
Why the front quarter window?
Because they are hidden behind the side mirrors so it’s less obvious to notice that it’s a stolen vehicle.
The cost of a broken window
A smashed window costs you both time and money
Having spoken to a number of customers, a replacement front quarter window typically costs about $400.00 to replace if it’s not covered by insurance. Even if it’s an insurance claim, there is still the excess to pay.
Even after it’s fixed, it’s still frustrating
It doesn’t matter how much care is taken to clean up the glass – you’ll be reminded about it for years to come. Glass fragments go everywhere! They fall down behind the trim, get lodged under the seats, and even fall into the air vents where they can rattle around whilst you’re driving.
It’s best that it never happens in the first place.
Glass-break sensor alternatives
Ultrasonic sensors are a far more effective and reliable way of protecting the internal space in a vehicle and would be my choice over a glass-break sensor every time.
Thatcham-certified alarms (CAT 1 and CAT 2-1) require movement detection, such as ultrasonic sensors or a microwave sensor, so glass break sensors are not approved under these standards as it is known that they may not work.
