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Comment by skulk | Hacker News Reader

Maybe a rock hurtling at terminal velocity straight towards your head (approximately) makes some interesting high frequency sound waves that only dogs can hear?

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No, they wouldn't. Sound travels at the speed of sound. That speed is the same regardless of the frequency (although it varies by temperature and air pressure). Supersonic things travel faster than sounds.

You could get around this by, say, making the air itself move directly towards the person nearly as quickly as the meteor, but that is probably safe to exclude as a possibility.

There is also Doppler effect, and dogs are known to be able to hear ultrasound.

Doppler effect doesn't allow sound go to faster than the speed of sound.

Dogs can indeed hear ultrasonic frequencies, but ultrasonic frequencies of sound, being sounds, travel at the speed of sound. Things that travel faster than the speed of sound go faster than sounds.

Did you see the picture and get the impression that the rock was traveling at supersonic velocities? Really?

Are you being serious? It's a known fact that meteorites travel many many times faster than sound!

When they enter the atmosphere, yes, but not when they reach the surface of the earth. Any rock-like object below ~15 m in size will reach terminal velocity before hitting the ground.

But this object was not traveling at supersonic speeds when it hit the house. Meteorites below a certain size slow down to terminal velocity long before they reach the surface.

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