An electronic device detects the presence of an animal such as a pet in a protected area and outputs a deterrent signal that preferably includes the voice of the pet's owner admonishing the animal. The animal is detected by sensing at least one of sound, heat, vibration, and motion. The deterrent signal may include loud noises, and signals audible to the animal but not to humans. The deterrent signal may also include bursts of light. The device can vary the nature and quality of the deterrent signal if the animal remains near the protected area for a predetermined time.