I frankly think there are better ways to control barking than the intimidation method just described.
Dogs bark because that's the only voice they have. When a boxer barks at something, generally speaking, since they are guard dogs, they are
alerting you to possible danger or something that isn't right. They have a job to do and should be allowed to do it.
If you yell at the dog to "Be Quite" he thinks you are barking too and will continue and do even more barking because he now thinks you are as concerned about the strange noise as he is. Never yell "QUIET" or "SHUT UP" to a barking dog. It will only make them bark more.
They can also make bad associations from intimidation practices. Say for instance your dog sees a person coming through your yard and barks. You go and squeeze your dog's jowls, give him a challenging stare in the eye and growl. The dog perceives that YOU are angry and that bad person who walked across the yard is the cause of the dog getting "punished." He then feels that anyone in his yard has the potential to cause him to be punished by his master, and he becomes even more determined to get that person off his yard by barking more and more and more loudly and more viciously. You defeat the purpose using NEGATIVE TECHNIQUES such as this.
Let me explain how I trained my dogs about barking.
When they found their barks as young dogs and were experimenting, etc., as soon as Maggie would bark at some strange noise or whatever, I would immediately say "Maggie, Thank you!" in a happy tone. This tells her that "I hear you" and you've done your job to alert me. Thank you." Beleive it or not, dogs do understand "thank you." This serves to interrupt the barking in a low key, positive way and redirects the dog's attention back to you.
Then I immediately got up, walked to where the dog was and looked. If it was nothing to be concerned about (usually the case), I would say "good guard girl, come!" and walk with her away from the distraction. Redirect her attention to play or cuddling or something else to reward her for a job well done.
As leader it is your job to protect the pack. So if you are alerted to something by your dog, it is YOUR JOB to thank them for their work and then DO YOUR WORK.
After a while, when the dogs become acclimated to this
consistent response to barking, and if you redirect them the same way each and every time, your dog will beging to "woof woof," then look at you for direction OR, woof woof and then go play with the toy you always give or come to your side and sit if that is how you have conditioned the dog to respond after you say Thank You.
So, now, when my dogs bark at something, if I recognize the sound (such as a car door or something) I simply say, "Thank you, Come" and they stop barking and come to my side. Then I pet them and tell them what good girls they are.
Sometimes I forget or don't say "thank you soon enough" and they woof woof, and then turn and look at me like, "well, we did our job, what's with you? Why aren't you thanking us?" Then they run to me to see what's wrong with ME!!
If this is about barking for attention or to be let out of the crate, don't give in to that demanding behavior. Ignore it. Don't give the dog ANY ATTENTION WHATSOEVER for this behavior and he'll soon discover that if he wants out of the crate or your attention, he has to be quiet and calm before he gets it and that barking won't ever get him what he wants. No need for intimidation. Just don't give the dog what he wants for bad behavior. Reward good behavior by giving the dog what he wants AFTER he displays proper behavior.
Consistency is the key. If you show your dog consistently how to respond to noises and what to do when they bark, they will learn it and do it all the time (unless of course there is something really wrong and they keep insisting. Then you definitely need to get up and check it out.) You'll begin to learn their barking sounds and know what is "just noise" and what is "potentially serious" in their tone and you'll be able to react accordingly.
Good luck.