Skimmed the internet some. Here is my impression of the consensus about dogs hearing relative to humans.
First off, there is quite a bit of individual variation, as well as variation by breed, but roughly speaking.
Humans and dogs have roughly the same range of peak frequencies around the few kilohertz range, where there hearing is most sensitive. In this range humans and dogs have about the same sensitivity (with humans winning by a few dB over most breeds). At lower frequencies, again, humans and dogs have roughly the same sensitivities, though dogs may be able to hear slightly lower frequencies than humans can.
At frequencies above the peak region, humans' sensitivity drops off more quickly than dogs' do, and dogs can hear much higher frequencies than can humans -- although not that well, the sounds have to be pretty loud for them to hear them in the ultrasonic range.
Overall, my reading of this is that dogs can hear sounds we can't because of high frequency, but they can't really hear things significantly further than we can. I think anyone claiming that a dog can hear an ordinary car (as opposed to a revved up Formula 1 race car) at 20 miles under natural conditions has quite a claim to back up.  |