You can buy sonic dog repellents. They are used for training. If it’s a continuous local problem it might be worth it. More than one dog is a problem like that, do you live in a city?
Thanks for mentioning that. I have thought about getting some spray or carrying something to protect myself and my dog. That sonic thing looks interesting and small, which is nice, but I don’t know how my own dog would react to it. I live in the county but the neighborhood is fairly developed and there is a lot of house there. The people with the dog in question have a fence for the dog but leave the gate open! The city has tougher leash laws. If I lived there they would have done something about it.