Before I will recommend using something on pet i.e. dogs and cats or any other animals for that concern I want to ensure no everlasting effect will cause permanent damage to their hearing or any other defects.  From the information I gathered that is not the case unless the frequency is above 45,000Hz for dogs and for cats over 64,000Hz.  On our site and the ones that we are selling are in those guide lines and I strongly recommend that you use the one that is listed on our sites because they are within the limit set and at the same time while walking you pets you will be in charge of any situation dealing with stray animals running around while you are on your walks with you pets.  Enjoy life and do not worry about the small things that that sometime get in your way and get the Electronic Dog Repeller that will make your walk more enjoyable.