Can people hear the CatScram cat repellent?

No. The frequency emitted by the CatScram is well outside the hearing range of humans and dogs. In rare cases, a cat may not respond to the CatScram. This happens because some cats lack the capability to hear noises as high pitched as that emitted by the CatScram. This is more common in older cats who have lost some hearing range, very young cats who have not yet fully developed, and ocassionally in rare purebreeds. No testing on other types of animals has been performed at this time.