They sound like an amazing invention. If I ever have a problem with barking dogs in my neighborhood, I will definitely look into these things.
For now, we don't have to worry about it. We live in an apartment complex which is extremely pet friendly, but dogs are not allowed to be left outside unattended. I see people walking their dogs on the property all the time but practically never hear a bark.
I'm not a dog expert, but in my experience, dogs that are nuisance barkers are often ones that are left tied up outside for extended periods of time, like the one Siwsan describes. From what I've read, being tied up like that is stressful for a dog. Here's an article that talks about the reasons why: https://trustytails.com/3-reasons-you-should-never-tie-up-your-dog-outside/
Basically, dogs can get stressed, lonely, bored, and anxious when they're tied up by themselves for long periods of time, and they express their frustration by barking. This is especially the case if the dog isn't getting enough quality attention from its humans. Dogs are very social creatures, and they thrive best when they have lots of opportunities to interact with other living tings like humans, their fellow canines, and/or other critters in the household.
As I said, I'm not a dog expert, but I read a lot, and I've watched plenty of dog training shows on TV. From what I've been able to pick up, a dog that barks constantly is almost certainly unhappy and not having its basic needs for socialization (not to mention training) met.
Unfortunately, there's not much most of us can do to fix things for a dog that belongs to someone else, and animal welfare authorities usually won't get involved except in cases of really blatant neglect or abuse. That being the case, I can't blame anyone for using an anti bark device such as one of these birdhouses to get some relief for humans and other critters in the vicinity.
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