Why Do Car Alarms Go Off to Loud Noises? — Like Thunder and Fireworks

Car alarms are a standard security feature in modern cars. They are designed to respond to a range of security threats, such as break-ins and auto theft. However, sometimes car alarms can be a nuisance. They’ll unnecessarily go off when there are no security threats, blaring out and disturbing the neighborhood. This includes going off to loud noises, such as thunder, fireworks, and gunshots. Why is this?

Why are car alarms triggered by loud noises?

Fireworks exploding near a BMW X1, highlighting why loud noises like thunder make a car alarm go off
Fireworks by a BMW X1 | Niklas Bischop via Unsplash

The car alarms in modern cars have a variety of sensors. This includes shock/impact sensors, door sensors, microphone sensors, and proximity sensors. All of these alarms connect to a computer system in a car. If one of these sensors is triggered, it will send a signal to the computer, and then the alarm is activated.

Each of these sensors serves a different purpose and has a varying degree of sensitivity. However, it is the shock/impact sensor that typically causes a car alarm to go off to loud noises.

Shock/impact sensors work by detecting a vibration — and sound, including loud noises, is vibration. Sound is composed of vibrating particles, and these particles bump into other particles, enabling sound to travel. The louder the sound, the more powerful the vibration — and louder sounds also travel farther away from the source.

So, when there’s a loud noise near a car, such as thunder, fireworks, and gunshots, vibrations travel and impact the car, which makes the car alarm go off. 

Sound is a powerful force that can make a car alarm go off

Thunder and lightning over trees, highlighting why loud noises trigger a car alarm
Thunderstorm with lightning | Max LaRochelle via Unsplash

Sound, while unseen, can be a powerful force. If you’ve ever played music loudly, you’ve probably felt the vibrations. 

Earlier in my career, I was a marine biologist. While in the waters of Hawaii researching singing humpback whales, the sound from one of the songs was so powerful I could feel them vibrate throughout my body. It was so strong that my body shook in sync with the soundwaves. This was especially the case for the low-frequency sounds, which carry more vibrational force.

And that’s essentially how the shock/impact sensors work for car alarms with regard to loud noises. Thunder, fireworks, and gunshots, which are loud and have a low frequency, not only can shake the air but also solid material, including a car. Loud, low-frequency noises shake the shock/impact sensor, making the car alarm go off. 

Can I turn down the sensitivity of a car alarm to prevent it from going off to loud noises?

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Does your vehicle have a problem with loud noises often making your car alarm go off? If so, then you can turn down the sensitivity of the shock/impact sensor so that the car alarm is not so easily triggered. While car alarms are a security feature, they are not a regulation. There’s nothing stopping you from reducing the sensitivity of the shock/impact sensor, or any other sensor, in a car alarm. 

However, it is generally recommended that you don’t turn down the sensitivity of a car alarm. The purpose of a shock/impact sensor is to detect impacts and hits around your car, such as the shock of a car thief breaking a window, as detailed by Warrantywise

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If you reduce the sensitivity of a shock/impact sensor, it might not be able to function as intended. A car thief could break into your car by smashing one of the windows, and then you’ll be out of luck.

Even a minor change in sensitivity could significantly diminish its sensitivity. There’s a fine line between a sensor making an alarm falsely go off and going off to a real threat. With this in mind, it’s better to err on the side of caution and not alter the sensitivity of an alarm sensor.

However, there are other things that cause a car alarm to falsely go off, including a malfunctioning sensor. Other causes include a low battery, a broken key fob, and wiring issues. If you’re unsure, then take your car to a service professional. They can get to the root of the problem and hopefully resolve it — and give your ears, and your neighbor’s ears, a break. 

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