Reviews of the Best Cat Repellents

Evidence that Ultrasonic Cat Deterrents Work

The only scientific study into the effects of ultrasonic cat repellents was carried out by Evans, Bradbury Nelson in 2006.  The study undertook a large scale investigation into the effect of ultrasonic cat deterrents as a result in a surge of interest from non-cat owners unhappy that their gardens were being used by cats, leaving their poo and faeces behind.
Often advertised as being the most cost effective and reliable method of keeping cats out of gardens, ultrasonic cat repellers grew in popularity until there were literally hundreds of different types from many different manufacturers. Back in 2006 when the study was undertaken, the team used one product, called catwatch. This exact product is no longer available, in fact if you search Amazon for “catwatch”, you will get a nice list of watches instead of cat deterrents! However, today’s ultrasonic cat deterrents offer more features and are more reliable than the catwatch from 2006 for the results you get today will exceed those of this test. For the purposes of this report though, I’ll list the specification of that catwatch device they used so you can compare it with any cat repellent device you are considering buying.
  • Detects heat up to 12m
  • Ultrasonic frequency range of 21-23kHz
  • Volume of 96 db falling to 44 db
You will generally find that any ultrasonic cat deterrent found on the market today will exceed those specifications, providing greater protection from cats.
The test was carried out by supplying two sets of volunteers (total of 63) with cat repelling equipment as detailed above. However to ensure the results were genuine, one set of volunteers unknowingly received devices that did not function. This is a common testing procedure, known as a double blind test.
However where this test kind of falls short, is that neither group were given guidance on how to set the device up, specifically, WHERE to set the device in the garden. I disagree with this part of the test. To measure the best possible result that this ultrasonic device was capable of, everyone of the participants should have been told to set up the device pointing towards the entry point that cats commonly used to gain access to the garden. We should bear this in mind when reading the results of the testing, and indeed the report summary did allude to this deficiency in the report.


The results compared both the probability of a cat entering the garden with an active ultrasonic device and without, and also, how long a cat stayed in the garden (again with and without a working device).


The results were very clear.  Volunteer’s gardens had a 54% chance of being visited by a cat before the garden was protected with an ultrasonic cat repeller. After the device was setup, the probability dropped to 34%.  This proved without a doubt that ultrasonic cat repellers did prevent cats from entering the gardens. If you factor in that the devices could probably have been set up better, as described above, then that figure could easily have fallen below 30%.

When cats did enter a garden, they were observed to stay for almost a full minute in unprotected gardens, but after an ultrasonic device had been placed the duration fell to as low as almost 30 seconds.
If you combine those two results for protected gardens, you can see that the effect of ultrasonic cat repellents is extremely positive, and supports why ultrasonic devices are so popular.
You can check our selection of Ultrasonic Cat Repellent reviews for more details.