A Simple Solution...Really!
I'm one of those people, horrible I know, who hates to hear dogs barking mindlessly.
When my boxer, Katie Scarlett, was a new member of the family we had a "learning experience".
Her first night, she was in her crate and started whining then barking. I was waiting outside the kitchen door. The first bark, the lights went on, I took her by the jowls to control her head and make her make eye contact, did a low growl. then went away.
"Hmmm" she thought, "that wasn't pleasant".
A minute or so later, she was whining and barking again. My reaction was the same, lights on, a stern unhappy growl and then leaving. It took about 20 minutes of this and she was quiet.
Of course, I made sure she'd hit the bathroom, so it wasn't a "gotta' go" pleading.
The next night, the same thing. It only took about 15 minutes.
The third night, she was quiet.
She also learned not to bark. If something/someone concerned her, she'd look at us and give a "grrrr" as a heads-up. No barking just because the neighbor's dogs were barking their brains out...she was a real lady.
She would go stay at a friends house when we'd be on vacation. Their dog would bark away, and Katie would look over her shoulder and give a quiet "woof", doing a Boxer smile the whole time.
She wasn't "crushed" or the least little bit curtailed by not barking, Katie was a dog who could go anywhere and be a perfect guest.
If you would like a quieter dog, now's the time to do it.