The Rats Are Fleeing – New Sound Technology Tricks Their Brains

Rat infestations are on the rise in Swedish cities, with the most severe problems reported in Stockholm, Skåne and Västra Götaland counties. Now, researchers at Luleå University of Technology have developed a method to combat rats without killing them. By using unpleasant sound signals, the rats are affected in a way that triggers their subconscious flight reflex. The rats leave the area.

“We have developed a way to simulate acute threats through sound for the rat. It is not about volume but about influencing the subconscious with the right type of signals so that the rat flees,” says Örjan Johansson, Professor in Engineering Acoustics at Luleå University of Technology and research leader.

The focus is on the brown rat, the only rat species found in Sweden. It grows to over twenty centimeters long, excluding the tail. Brown rats thrive in basements and sewers. They can gnaw through almost anything, damaging buildings, and food supplies, and can spread viruses and bacteria to humans. As rat problems grow in urban areas, legislation around chemical pest control is becoming stricter.

“Our sound technology can create entirely new opportunities to keep pests away without using poisons or causing unnecessary suffering,” says Örjan Johansson.

In the research study, the technique of repelling rats with ultrasound was tested on brown rats through field trials in controlled environments. The experiment was conducted in three different spaces: a room, a corridor, and a storage area in a multi-family building with documented issues with wild rats. The sound patterns are designed to trigger the rat’s limbic system, the brain’s centre for fear and survival. The signal’s time characteristics mimic a warning sound that rats themselves produce by grinding their teeth, and peak levels exceed 100 dB at a distance of one meter. The technology is based on years of research in bioacoustics and sound design, where sound signals are modelled to elicit specific reactions and effects.

“It is about tricking the brain into believing something dangerous is approaching, without it actually happening. Unlike simpler electronic deterrents, which animals often get used to, these signals are designed to provoke a reflexive response,” says Örjan Johansson.

The research study on designed sound signals for rats is a collaboration between researchers at Luleå University of Technology and the Swedish University of Agricultural Sciences (SLU). The study is part of a larger research initiative in bioacoustics, where researchers examine how different animal species react to sound. The research group has also observed early results of reflexive flight behavior in mosquitoes and marine animals such as seals when exposed to species-specific designed sound signals.

“We are seeing promising results across several species, but rats are the first animals where we can demonstrate a scientifically validated effect in practical tests. We are now continuing to map out exactly how sound signals should be generated and designed in relation to different species’ perception,” says Örjan Johansson.