Dogs feel threatened when they're approached by someone with whom they're not comfortable. Many dogs react negatively to men who are tall, have deep voices, broad shoulders or facial hair. Treating this negative reaction may take time, because barking is just a symptom. If your dog is barking at your husband, you have to change the way it feels about him.
There are "no-bark" collars, muzzles and leashes on the market that claim to help your dog stop barking. It is true that these products will cause your dog to stop barking, but it will not help your dog to feel more comfortable with your husband, so your dog will most likely continue to bark at your husband once you take the training product off.
You should involve your husband when training your dog to stop barking at him so that your dog can learn to stop feeling threatened. Have your husband present himself as less of a threat by turning slightly to the side in the dog's presence, leaning slightly away from the dog or squatting when entering the room.
You can also make your dog associate your husband with good things, like a treat or a favorite toy. Have your husband enter the room with the treat or toy in his hand. Your dog may bark at first, but command it to stop by saying "no bark" in a commanding voice. When the dog stops barking, have your husband give the dog the reward. If the dog shies away from your husband at first, he may have to toss the reward to the dog, but eventually the dog should be comfortable enough with your husband to take the reward from his hand. The key is to give the dog the reward before it begins acting negatively again.
According to Dog Time, this training process may take a long time. While your dog is learning not to bark at your husband, do not comfort it, even if it seems scared. When you comfort your dog in this situation, you are affirming that there is something to fear. While your dog is in training, show it that there is no reason to be afraid of your husband, and eventually, your dog will come around.