Your dog's barking may be a response to something he's afraid of if:

• The barking occurs when he's exposed to loud noises, such as thunderstorms, firecrackers, or construction noise.
• Your dog's posture indicates fear—ears back, tail held low.

Recommendations:

• Identify what's frightening your dog and desensitize him to it. You may need professional help with the desensitization process. Talk to your veterinarian about anti-anxiety medication while you work on behavior modification.
• During thunderstorms or other frightening times, mute noise from outside by leaving your dog in a comfortable area in a basement or windowless bathroom, and leave on a television, radio, or loud fan. Block off your dog's access to outdoor views that might be causing a fear response, by closing curtains or doors to certain rooms. Avoid coddling your dog so that he doesn't think that he is being rewarded for his fearful behavior.