First of all, here's a quick management solution while you educate your dog about this new situation: Limit his access to the "guilty" window.
I've had this problem with my dog too when I moved from Belgium to France. And I know how difficult it is, especially during the night. The first thing I did was to cover the window with an opaque fabric and put obstacles so he couldn't get to the window. That's just management and it doesn't solve your problem. But at least you can get a good night's sleep.
The next step is this behavior modification called "desensitization". It simply means that you'll get your dog to associate something positive with whatever it is that's triggering him outside the window.
For example, when your dog hears that noise, you immediately feed him a tasty special treat that he usually doesn't receive. Get that treat into his mouth with the speed of light, before he gets to bark. Like, when he's breathing in preparation of a bark.
Feed him this special treat each time the noise happens. After enough of these repetitions, he'll start to drool when hearing that noise and he won't be afraid anymore. So he won't have a reason to bark anymore.
Now, I realize this might seem like a daunting task, because you can't predict when that noise happens. But it's actually easier than you think. You only need to make the noise predictable. So ask a friend to make that noise outside the window. This way, you get to control the situation.
You can do three 15 minute sessions per week and it shouldn't be long before your dog is ok with whatever happens outside the window.
But until then, make sure that you cover the window when you're not doing the training.
Please, let us know how it goes
P.S.: Do the same "desensitization" for all the window related triggers. So, when he sees the thing outside your window, immediately feed him the tasty treat. Just like the noise desensitization.