Works great on medium sized dogs but we have 2 chihuahuas next door that could care less

I do have to use this once in a while when a neighbor 2 doors down leaves his dog outside at night and the dog keeps barking

The dog stops barking once i turn it on outside in the backyard

The instant his family puts him outsidewhich they do several times a night between 11 pm and 3 am in complete defiance of city noise ordinanceshe starts to bark twice per second in an unrelenting staccato rhythm that is unlike anything ive ever heard from any other dog and he sustains this barrage until he is let back inside