There is an owl nesting in a tree immediately adjacent to my property. It hoots continuously from very early AM on into the wee hours making it difficult to rest or watch TV. I am a disabled senior doing battle with 3 life threatening health problems and sufficient rest is key. Will an Ultrasonic Sound Generator used to control other animals and birds have any effect on the owl?

No, these devices have not proven successful in repelling wildlife. I do not think it would have any impact on the owl. The owl (and its nest and young) is protected by federal and state law, but I understand that you need your rest, especially if you are dealing with health issues. I would recommend that you call the local Illinois Department of Natural Resources district wildlife biologist. I will send you the contact information for the biologist in your county.