growling dog!

[stevieb]

help! i have a 3 year old schnorkie who growls all the time! any time a car drives by or someone walks by our door or it thunders, he lets out a low growl. we scold him and he just continues to do it! my dog, steve, has had issues with training but has done so well the last year since my husband has worked with him but this growling thing is out of control and we have tried everything! he doesn't seem to be really aggressive with it (his ears stay perked up, his fur isn't standing up, and he doesn't show his teeth) does anybody have any advice???