What kind of mix, do you know? Have you owned the dog since he was a puppy? What relationship does the dog have with your husband versus you? Who is/was the trainer, disciplinarilan? Does this dog have a dominant personality? Is he challenging your husband for alpha or is this behavior shown out of fear? How does your husband approach the dog in normal circumstances? In the agressive circumstances? Has ever attempted to bite or is he just threatening with his voice? What is yours and your husbands response to this behavior?
If we can get a better idea of what is happening someone here might be able to gear you in the right direction.