Ultrasonic Rat repellers have been on the market for over forty years. But despite hundreds of models and thousands of promises, only one product - Repello - has been scientifically tested and shown to be effective against rats. This is according to Professor Örjan Johansson at Luleå University of Technology, who led the research behind the technology.
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- Many products are marketed with big words, but lack any scientific basis. It is not uncommon to see devices being sold that basically do nothing at all," says Johansson.
Both Swedish Consumer Agency och National Association of Homeowners has long warned against misleading marketing of electronic pest controllers. As early as the 1990s, Villaägarna described large parts of the market as "bluff product"However, the product was cancelled because the devices had no documented effect. The Swedish Consumer Agency has repeatedly pointed out that companies claiming efficacy without scientific evidence may be guilty of misleading marketing - which can lead to bans and sanctions.
Common scams - and why they're not true
❌ "Covers up to 300 square metres"
Many devices claim to cover huge areas - sometimes entire houses. But ultrasound doesn't work that way.
- High frequency sound waves are quickly attenuated in air. Even after a few metres, the effect is very weak. It is therefore completely unrealistic that a small device could affect an entire house," explains Johansson.
In laboratory tests, it has been shown that the effect diminishes drastically within 2-3 metres, depending on the room. Claims of "hundreds of square metres" are therefore ren bluff.
❌ "Goes through walls"
Another common claim is that sound travels through walls and spreads between rooms. But this is physically impossible.
- Ultrasound is effectively stopped by solid materials such as wood, concrete and plaster. "If you have the scare in the kitchen, you can hardly hear it in the living room," says Johansson.
Ultrasound cannot penetrate walls, furniture or floors. Therefore, it requires a device in every room if you want to cover multiple surfaces - but most scam products never mention that.
❌ "Sends pulses through the power grid that scare away rats"
Some manufacturers claim that their devices "send electrical pulses" through the house's electrical wiring that are supposed to create vibrations or disturbances that scare rats into the walls. It sounds technical - but it is ren bluff.
- Sound and electricity are two completely different things. Sound is the mechanical vibration of air, while electricity is the movement of electrons in metal wires. Sending out small electrical pulses in wall sockets cannot affect rats at all," says Johansson.
In addition, such weak signals are filtered out by transformers, fuses and appliances in the home. No scientific study has ever shown that mains-based scarers work.
The discovery - the secret language of rats
Repello is based on several years of research in bioacoustics and animal behaviour vid Luleå University of Technology (LTU), led by Professor Örjan Johansson.
The breakthrough came when researchers discovered something that had long eluded science: that rats communicate danger through a special tooth squeak - an ultrasonic warning sound that only other rats can hear.
- When a rat feels threatened, it grinds its teeth in a specific way. The sound acts as a reflexive warning to the pack - a sign of mortal danger," explains Johansson.
For other rats, this sound is an immediate signal to flee.
Just as humans pull their hand away from a hot surface without thinking, rats react to their warning sound instinctively - it triggers pure panic.
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The science behind the technology
The research team at LTU analysed and recreated the natural warning sounds of rats using high-resolution sound analysis.
By reinforcing and varying frequency, pulse and rhythm For example, they can create a signal that mimics a dominant, aggressive rat - a sound that other rats interpret as a direct threat.
- Rats don't need to learn to escape from sound. It's deeply programmed into their nervous system," says Johansson.
Together with Swedish University of Agricultural Sciences (SLU) The technology was tested in both laboratories and real-life environments.
The results were unequivocal: the rats fled the area immediately when Repello was activated - and did not return, despite the fact that both food and shelter were still available.
Repello is therefore the the only rat repellent in the world with proven scientific efficacy, based on the rats' own language.
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