I think it's probably a cat scare device. I have one and sometimes it activates from neighbors walking by my gate. It's the same sound but softer..
Like this: https://www.amazon.com/Powerhouse-Products-LLC-Electronic-Repellent/dp/B003HHFW8S
But you have them for raccoons too, or humans indeed. It depends on your location what's logical for your neighbor to have..
Creo que los gatos odian los citricos, asi que se podria armar algo con eso. O algo con sonido (?) https://www.amazon.com/Powerhouse-Products-LLC-Electronic-Repellent/dp/B003HHFW8S