The ultrasonic sound cat deterrent is recommended by the RSPB. It’s effective between 22-46% of the time and is therefore moderately effective in deterring indoor/outdoor cats from coming into your garden. If they get past the barrier of high-pitched sound, they spend less time in the garden because it is uncomfortable. This device is one of the few which actually works to a certain extent. There are many proposed methods of deterring a neighbour’s domestic cat from coming into your garden or backyard but many are ineffective.
The ultrasonic cat repellent should not be audible to people because if it is, it’s not going to work as there will be a background noise permanently in your backyard or the backyard of your neighbour if they have one. The objective of this device is that it is audible to domestic cats but not to humans because they can detect ultrasonic sound and humans can’t. They can deter foxes too and other wild animals able to hear high frequencies.
Ultrasonic sound describes sound frequencies greater than 20 kHz (20,000 Hz – 20,000 cycles per second). Humans in the prime of life can hear noises up to about that level but it sinks to around 12,000 kHz at retirement age. Cats on the other hand can hear sounds up to a maximum of about 100 kHz according to Dr. Desmond Morris in his book Cat World.
So ultrasonic cat repellents make a noise which is beyond the normal ability of people to hear. My research indicates that they make a sound between 30 and 55 kHz. This fundamental fact makes them useful and acceptable to people. However, there is a story in the Mirror newspaper today about a mum who became disgruntled because her neighbour fitted multiple ultrasonic cat repellents and she can hear the noise.
She said that it makes it “really uncomfortable” for her to use her backyard. She explained that she hears a “very shrill” noise. She’d heard it for several weeks and couldn’t work out where it came from until she did some research online and discovered what was going on.
In fact, she doesn’t have to be in the backyard to hear it because when she is in her home with the windows open, she picks it up. And as we are in the summer months, her windows are going to be open a lot.
She posted her complaint on the website Mumsnet and said: “For the past few weeks I’ve been hearing a really high-pitched sound while in my garden. It’s very shrill and has made sitting outside in the sun really uncomfortable because it’s like a needle feeling in my ears. It’s coming from various parts of my next-door neighbour’s garden, sometimes multiple bleeping at once.
“I did some Googling and realised the sound could be ultrasonic cat detectors, although my research suggests they’re meant to be inaudible to humans. I popped next door to ask them and see if they did indeed have these deterrents in place.”
She found out that they have five in their front garden. They installed them to prevent cats from pooping on their lawn and they also have some in their backyard. It is possible that the high number of devices makes them audible to this lady.
The mum claims that she hears them more in the sunshine and they give her a headache. She claims that they go off more in the sunshine. When it rains, she can barely hear them. Note: this may be about sound transmission rather than the devices going off more.
Clearly, this is not meant to happen. It would seem that this lady’s hearing is particularly acute at high-end frequencies which is very unfortunate. This is bad luck because ultrasonic cat repellents are quite unusual. And it is also unusual for a person to be able to pick up the sound that this device makes. Two unusual circumstances have come together to create an intractable problem. The only solution is for her neighbour to remove the ultrasonic repellents which they will be reluctant to do. Lastly, you do not want an argument with your neighbour. That’s the last thing you want.
Below are some more articles on a cat’s hearing.