Sunday, May 18, 2014

Slowing Down Sound So That You May Hear It?

Sometime you just have to shake your head at how badly science is mangled.

This is a "verdict" on the latest Godzilla movie. Of course, one doesn't expect accurate science reporting when it is an article on such a movie. Still, read this passage at the very end and tell me if you can't find, in this single paragraph, a couple of really glaring and puzzling errors.

But what you think you are hearing with that Godzilla roar may be deceiving. The roar is actually a decibel beyond the human range of hearing, so the design duo used special Japanese microphones to slow the sound so it falls within audience's hearing range.


A "decibel" measures the sound "loudness" or intensity. A sound may be too loud for a human being to hear comfortably, but it certainly isn't outside a human range. So to say that the roar is "a decibel beyond the human range of hearing" is rather puzzling.

But the kicker comes next where you can actually use these "Japanese microphones" to slow the sound, and thus, make it fall within the hearing range! I can understand the microphones picking up these ultra or sub-sonic sounds and then alter the frequency so that it falls within the hearing range. But slowing down the sound so that you can hear it?

I suppose if the microphone itself is filled with some dense medium that actually changes the speed of the incoming sound. But if we use our understanding of light going from one medium to the next, we see that the frequency remains constant even when its group velocity and wavelength change from one medium to the next. So I don't see even via such a picture, how one would "slow down" sound and make it fall within the hearing range.

After the earlier mistake being made on what a "decibel" is, I suppose it is hard to take anything written down after that seriously. So I am definitely making a big deal out of a mole hill.


1 comment:

johnduffieldblog said...

You sound like me when I complain about two photon physics. This bit:

"From quantum electrodynamics it can be found that photons cannot couple directly to each other..."

Oh yes they do! Pair production does not occur because pair production occurs. Spontaneously. Like worms from mud. A photon does not spend its life morphing into an electron positron pair which then morph back into a SINGLE photon which nevertheless manages to propagate at the speed of light. See turning light into matter re Breit-Wheeler.