20-Mile skeptikal argument

[Bonteburger]

Hi!

I usually lurk here and read a little. I don't think I've skipped a Skeptiko episode since its inception in Feb '07 though!

An argument against dog telepathy made me do a mental doubletake - it went along the lines of "well, dogs can hear the individual hum of a car from 20 miles off, you know" but I couldn't find anything on google about it (yet).

I know that Polar bears are supposed to be able to SMELL a seal from 20 mlles away in the binding whiteness of the arctic.

Hearing an approaching car's special whine against the noisy backdrop of a Californian city, hmmm... other story?

250 yards is all I could come up with yet (I'm not very good at imperial but I do know it's a considerably shorter distance). The 20-Mile-debunk argument came up in the youtube comments. Can anyone substantiate this?

If true, it would require that some changes be made to the experiment.

Marco

[Topher Cooper]

It is possible, I suppose though it seems unlikely. An ordinary, running, car engine is roughly the same loudness as human conversation. So we are talking about the ability to hear someone talking at 20 miles away.

I judge it on the edge of plausibility that when measured at the ideal frequency spectrum for a dog, under conditions of complete acoustic shielding a difference of this magnitude at the maximum sensitivity level for dogs might just be discernible by a dog (probably with a high error rate).

The ability to do reliable recognition of such a sound at that level in a natural, noisy environment, with many almost identical sounds seems very implausible to me. It might be worthwhile, though, for someone who is a little less rusty on acoustic physics run the numbers and see what this claim actually amounts to.

[Topher Cooper]

I just did a quick calculation. Assuming I didn't screw it up (a big assumption -- I really don't remember my acoustics unit in physics very well) then this would require dogs to be able to hear sounds 21dB below the threshold of human hearing, or, roughly speaking (so to speak), sounds 100 times lower intensity than humans can hear. I don't know how well dogs can hear relative to humans but I would say that being able to hear 2 or 3 times better than humans would be impressive. Although they can definitely hear sounds higher than we can I have never had any reason to suspect that dogs can hear more than a bit better than we can in our overlapping range.

And of course, the difference between being able to detect a small difference under ideal conditions (what we mean by the threshold of hearing) and being able to reliably differentiate a complex sound from among a cacophony of similar and masking sounds is still apropos -- unless you are planning to conduct your tests in the middle of a deserted arctic ice-field when the air is still and the ice is stable.

[Topher Cooper]

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.