We often get asked what is the difference between and audible cat repeller and an ultrasonic cat repeller?
To put it simply, audbile means that the sound the cat repeller unit produces can be hear by humans. Ultrasonic sound is outside of the human hearing range and so it cannot be heard by humans.
The sound is so high pitched that only cats can hear it. They find it anonoying and so want to leave the area. Its not harmful, just annoying. And very effective!
If you have cats using your garden as a toilet, this is an inexpensive way to sort out the problem.