Why do dogs howl when they here the siren of an ambulance or a cop car passing by?

This is because the siren Is a loud pitch sound and since dogs hearing is very sensitive it hurts their ears. So since dogs can't talk the howl when their ears hurt from loud noises.

Many dogs howl at sirens because they are loud and they sound kinda like howls to dogs so the dogs howl back.

maximum individuals assist you to recognize that it hurts their ears, yet that isn't the case. in the wild, dogs howl to speak with others of their very own species. in the sirens there's a tone that instinctively reasons the dogs to howl.

Well as far as I'm concerned these noises hurt my ears & a dog's hearing is way more sensitive, so I imagine it is somewhat upsetting for them to hear these high pitched noises.

More than likely the noises hurt the dogs' ears. They have more sensitive hearing than humans do.

I was actually wondering the same question. So I asked my dad and he said that it was because it was high pitched, and dogs have like 10x better hearing then us, so it hurts their ears....just like what the other answerers said