If your pooch has a penchant for howling noisily any time he hears a loud sound, he's not trying to disturb the peace. Howling along with chaotic, often high-pitched sounds isn't your dog's attempt at auditioning for a singing contest, but probably an effort to communicate with a perceived fellow canine.
Domestic dogs are closely intertwined with their wild family members -- think wolves and coyotes. On a whole, these species are highly companionable and social creatures -- they usually do things in groups, rather than independently. One of the key facets of social behavior in animals -- as in humans -- is communication. Your dog may howl when he hears specific sounds because he believes that there is another dog -- somewhere in the distance -- howling to him first. By howling along with the initial sound, your dog may be under the impression that he's having a conversation with an imaginary dog somewhere. Howling back to sounds is generally an innate canine reaction.
It is especially common for dogs to howl alongside sounds that are of higher pitches -- think ambulance sirens, soprano singing and flute music, for example. Piercing, extended noises are reminiscent of their own howling sounds. If a dog hears a persistent and noisy lawnmower coming from directly outside your home, he probably won't howl back to it. After all, there's a slim chance that he'll mistake it for another doggie's howling communication attempt.
If your dog is howling nonstop and there happens to be a siren going on in the background, you may notice that once the sound moves off into the distance and fades away completely, your pooch becomes silent too. This means, simply put, that the "conversation" is over. The "howl" is no longer happening, and your dog isn't howling back anymore either.
When it comes to your dog's well-being, you can never be too cautious. If your dog's howling seems excessive, it may not be related to noise levels at all. If you live in a bustling urban environment, don't assume that your dog's vocalizations necessarily have anything to do with street traffic or the bickering neighbors next door. Immoderate howling in dogs sometimes can indicate health and emotional issues. Whether your dog is stressed out over not being able to find a beloved toy or over intense stomach pain, it's up to you to investigate the situation further by taking him to the veterinarian. Don't wait around.