Hello mate, I know exactly what you're experiencing.
My neighbour has 5 dogs.
It started with a large dog, then a snoopy type breed, and then the little brown fox-like canines with their shrill, high-pitched bark.
Having lived in different countries, I'm used to dogs barking at all times of day, but these little dogs have a special kind of piercing sound that goes right into the middle of your skull!
Initially, I talked to my neighbours and she was quite obliging about it and would take them inside after a certain hour. Feeling that she was up for being helpful, I sent her some details I found online, such as an anti-bark collar, and also the idea to leave a radio on when they left the dogs alone, as it is often the case that the dog misses the owner when left for extended hours.
There's my first suggestion, gently bring up the barking with them, as they may not realise it's being a nuisance to you.
In my case, the noise subsided, was controlled/monitored for a while. Then it went back to the same. I kept texting the lady whenever it bothered me, and at one point she started complaining that I was being a bully. I then started telling the husband about the noise.
One day, the dogs were barking at 11pm and I called him to say the dogs are barking and it's disturbing me. His answer was, "well, they're dogs, that's what they do!"
I then contacted my council about it. They asked me to keep a diary of the noise for 2 weeks, and then send it in to them. I did that and they then came round and installed some expensive noise recording equipment for a week.
They also visited the neighbour to assess the living conditions of the dogs, and despite them being left alone for the entire day in the garden, it was assessed that the dogs were healthy and happy. Go figure... they're NEVER taken out of the house for a proper walk!!!
The idea is that you record the noise whenever it disturbs you, and then at the end of the week they take the machine away and assess whether the noise levels constitute a nuisance or not. Sadly, I was unable to continue recording over the whole week due to some personal stuff.
I will be making a new diary and then resubmit the complaint. Apparently each residence is allowed 4 recording attempts.
It's a strange scenario where the onus is on you to prove the noise is a nuisance rather than sensibility taking over and seeing that 5 dogs in a garden space of 15x20ft left alone all day long will very likely bark for no apparent reason! I feel sorry for the dogs that they don't get out for walks at all, to a park to sniff a new dog's arse :-P, or experience the various smells that dogs enjoy by being out n about. But apparently the council expert thinks the dogs are doing fine!
I don't hold much hope that a 2nd complaint/recording will achieve a different result, but I will keep trying. The final recourse is private legal action, which is basically the end of the "friendly" neighbour facade!
So, I'd say, if talking to them doesn't help, you'd need to call your local council and see what their procedure is for dealing with noise complaints.
Good luck!