What's going on that we can't hear? - Kawasaki KLR 650 Forum
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post #1 of 27 Old 05-31-2013, 02:16 PM Thread Starter
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What's going on that we can't hear?

I've wondered this for a long time.

Do bees make a lot of noise, but we just can't hear it?

Dog's can hear up to 65kHz. What do they hear?

Earthquakes and volcanoes make low frequency sounds. Is the earth groaning all the time and we can't hear it?

Is there a way to frequency shift sounds down or up into our hearing range so we can listen?

There doesn't seem to be a lot of information out there, but I'm trying to digest this.

T

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post #2 of 27 Old 05-31-2013, 02:31 PM
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Interesting theory or thought....but isn't there machines that can amplify sounds so we can hear them now? I don't know?

Plus is there a condenced version of that report? Yep....I not only can't hear bees etc I'm frig'in lazy!!!

Willys
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post #3 of 27 Old 05-31-2013, 02:46 PM
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Now you've done it!

I got into chapter 4 but intend to go back to it. I used to work on Guitar amplifiers and would hook up an audio oscillator and scope to them and crank the freq and the amplitude up at night(in the shop. I could see the waveforms being reproduced in the amp and wonder why the neighbors and their dogs were not sending the cops to my house. I finally guessed that the speakers were not capable of reproducing those waveforms('course the amp would give up also above certain frequencies....) Now - IF I could just stop this ringing in my ears! -Then, maybe I could tell whether that tree falling in the woods, when no one was around, made a noise!

Thanks, Tom(& again for the tutoring on posting new thread....).

Jim

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post #4 of 27 Old 05-31-2013, 03:28 PM Thread Starter
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Quote:
Originally Posted by willys View Post
Interesting theory or thought....but isn't there machines that can amplify sounds so we can hear them now?...
It's not amplification, it would be shifting the frequency.

What I'm wondering is if we could take a sound that is generated in the 35kHz to 45kHz range (maybe a humming bird singing "I'm A Lumberjack And I'm OK" and shift it down into the 5kHz range so we can hear it.

I think the effect would be similar to listening to someone say "I'm happy I live in a split level head" while they've inhaled helium, then listening to them say the same thing breathing normal atmosphere.

It would not be sped up or down like when Yello sang at normal speed, then set the replay to 1/3 speed during the recording of "Oh Yeah"


It would just be a shifted frequency. You'd need a microphone with a response in the right frequency range. I think most commercially available ones only cover the normal human frequencies.

T

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“'Why' and 'How' are words so important they cannot be too often used.” -Napoleon Bonaparte


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Last edited by Tom Schmitz; 05-31-2013 at 03:34 PM.
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post #5 of 27 Old 05-31-2013, 03:48 PM
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Quote:
Originally Posted by Tom Schmitz View Post
Is there a way to frequency shift sounds down or up into our hearing range so we can listen?
The short answer is "yes", but I don't know the technical details. But I'll bet a pint a Fourier transform is involved.

I saw a presentation on bat songs, and the researchers had recorded the bat sonar sounds and shifted them down in frequency so we humans could hear them. It was pretty fantastic to hear.

Autotuners also work by changing the frequency of the sound without changing the duration. Hmmm. Let me search on that.

Here we go. You're interested in phase vocoders. I guess no one's going to take me up on the bet, now. Oh well.
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post #6 of 27 Old 05-31-2013, 03:54 PM Thread Starter
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Beej, you're a damn genius, you are.

Phase vocorder. No wonder I couldn't find anything.

I want one of those.

I have to read the wiki, but do you happen to know if the dynamic range is compressed when the frequency is shifted?

If the humming bird sings with a range from 35kHz to 45kHz, would the transformation maintain the range such that we'd hear it from 5kHz to 15Kz, or is the transformation done such that the range is proportional?

I really want one of those...

T

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post #7 of 27 Old 05-31-2013, 04:06 PM
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Beej, you're a damn genius, you are.
Nah, I just took too much math in college; just enough to be dangerous, but not enough to know anything.

Quote:
I have to read the wiki, but do you happen to know if the dynamic range is compressed when the frequency is shifted?

If the humming bird sings with a range from 35kHz to 45kHz, would the transformation maintain the range such that we'd hear it from 5kHz to 15Kz, or is the transformation done such that the range is proportional?
That's a good question, but I don't know the answer. My gut says it would be a proportional transformation... but then part of me thinks the algorithm would let you decide how wide the range should be. I'm not sure enough to bet pints on this one.
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post #8 of 27 Old 05-31-2013, 04:14 PM
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That's a good question, but I don't know the answer. My gut says it would be a proportional transformation...
I did some more skimming but didn't find the definitive answer. It does, however, look like most of the phase vocoder software accepts a multiplier for the pitch, so you'd alter the pitch by 2.0, and it would change your frequency from 35-45 kHz to 70-90 kHz.
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post #9 of 27 Old 05-31-2013, 04:20 PM Thread Starter
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All I need is a Panasonic WM61A and some software...

Gad, as if I don't have enough to do.

T

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“Neither of the two people in the room paid any attention to the way I came in, although only one of them was dead.” -Philip Marlowe

“'Why' and 'How' are words so important they cannot be too often used.” -Napoleon Bonaparte


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post #10 of 27 Old 06-01-2013, 12:29 AM
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Quote:
Originally Posted by Tom Schmitz View Post
Do bees make a lot of noise, but we just can't hear it?
T
I've had an uncanny ability to hear bees all my life. If you get a lot of them together in one place, they make a hell of a lot of noise...........

Seriously, though, interesting question to pursue.



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