First time I heard Sonic howl was in his sleep, one time while sleeping he started howling and he sit up *he was still sleeping* and I was like sonic you ok and pet him and he layed back down lol.. I think he has vivid dreams he seems to act them out, his tail wags, one of his paws moves like he is swimming, sometime he runs or howls lol. This happened like a week ago me and one of my niece's were on the way to town to pick up Chinese food I had to make a stop at grocery store for a few items, my niece stayed in the car when I came back she said sonic gave a little howl. I think it is sooo cute when he howls.
here is a video of him howling he howls if im not home.