1. Mic
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    Mic New Member

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    Measuring hearing acuity?

    Discussion in 'Research' started by Mic, Jan 4, 2015.

    I have a character who wants to describe how good his hearing is. I'm wondering if there are ways of measuring this (the way you can say you have 20/15 vision). He is a very scientific and analytical character, so I'm looking for something very clinical and technical that he can use to explain just how good his hearing is. It's okay if it's not colloquial or layman, in fact it's better if not. Any help would be much appreciated, thank you!
     
  2. GingerCoffee
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    GingerCoffee Web Surfer Girl Contributor

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    Hi, welcome to the forum. There is no equivalent to 20/20 when it comes to hearing. He might discuss having an incredible range.

    Normal human hearing frequency range is from about 20 Hz (low) to about 20 kHz (high) but some people can hear outside that range. So he could say that he can hear as low as 12 Hz (which some people can actually hear) or higher than 20kHz (more controversial, most sources say 20 is the maximum frequency the human ear can detect).
     
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  3. Mic
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    Mic New Member

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    Thank you, this is very helpful!

    Do you know if there is a way to measure the loudness or softness of sounds as well? Perhaps in decibels, like is there a very low number that is hard for the human ear to detect? Or is frequency really the only measurement for individual hearing?
     
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  4. GingerCoffee
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    GingerCoffee Web Surfer Girl Contributor

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    Audiology exams generally combine decibels with frequency. Look at exam chart results:
    [​IMG]
    Range is tested with an increasingly louder stimuli. The result gives one a threshold where the frequency is detected. Normal results include the decibel the frequency is heard at and human hearing norms are established within this range.
     
  5. Jack Asher
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    Jack Asher Wildly experimental Contributor

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    Remember that the audible decibel system is on a logarithmic scale. Every six decibels the "loudness" is doubled. So a 120 decibel sound is twice as loud as a 116 decibel sound. On the low end you can hear anything down to 0 decibels. Obviously anything lower then that would be impossible to exist. That's the "threshold of hearing". On the high end 120 decibels is the absolute loudest your brain is able to process. Anything louder than that will only register in your senses as pain. That's the "threshold of pain".

    Hearing loss can be experienced at anything from 60 decibels and up, depending on the person. I would say it's very unlikely that your character would use this as a measurement to describe how accurate his hearing is, because exposing himself to loud noises would make his hearing less accurate.

    I would have him express his sentiments anecdotally because there's very little to go on. Humans are very rarely exposed to frequencies over 20khz, unless they work as a dog whistle tester. Which now that I right it doesn't seem like a job that should exist.
     
  6. SwampDog
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    You can express the fact that he's scientific and analytical, without going into detail. Could detail bore the reader? Don't know in your book. Is there room for a little humour?

    For example: (Character) went on to explain how he used to be involved in the testing of navy sonar ratings, exploring the limits of human hearing. In other words, he could hear a gnat fart at fifty paces.
     
  7. !ndigo
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    Actually, contrary to what most people would assume, you can have negative decibels. You can think of it as like the Celsius scale where water freezes at zero. For dB, zero is the quietest thing humans are able to hear (assuming no hearing damage).

    It would be next to impossible to have a negative dB environment in real life though, they tend to be created in special labs for experimental purposes.

    http://www.smartplanet.com/blog/thinking-tech/quietest-place-on-earth-causes-hallucinations/
     
  8. GingerCoffee
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    I didn't know that. I've always thought of it as the measure of the amplitude of the wave. I found this simple explanation (compared to Wiki which was confusing to a non-physicist):

    Though Wiki does include some interesting history of the term. The term evolved from Bell labs using a measure of sound lost over X miles of telephone lines.
     
  9. Jack Asher
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    Jack Asher Wildly experimental Contributor

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    That's why I specified the audible decibel scale. There are two others, the dBM scale, and one that I can't remember. My audio recording class was a long time ago.

    Edited to add: oh it's dBf. That's the scale that can have a negative decibel because it's not real noise, it's just a signal running through digital equipment.

    Edited some more: The temperature analogy is not actually correct, because while you can have a temperature below freezing you can't have a temperature below 0 kelvin. Those audio rooms that filter out echos (which is what they're there for) don't create a negative decibel, the just remove all the noise environment to which you are constantly exposed. Without that you can hear the blood pumping through the capillaries in your ears.

    This is still not a negative decibel.
     
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  10. Mic
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    Thank you all very much for the advice and links! It sounds like bragging about being able to hear something as low as 0dB would not really be a thing? Nor would it be possible to say one can hear negative decibels?
     
  11. Jack Asher
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    Jack Asher Wildly experimental Contributor

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    Well you could brag about hearing something .0000001dB. But there's a room that allows you to hear noises that small. No one has managed to stay inside for more then forty minutes. As mentioned, you can hear the blood pump through your ears, listen to your stomach gurgle, and the rustle of your cloths become a cacophony. Not something that your brain is prepared for.
     
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  12. GingerCoffee
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    Depends on if you are writing a superhero character or something closer to reality. If you want superhuman but within reality, I'd go with a range down to 10Hz and maybe mention the decibels as being able to hear 20Hz at 'close to zero decibels', something like that.
     
  13. Jack Asher
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    Jack Asher Wildly experimental Contributor

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    If there's some flexibility in the story, you might have him turn down a pair of noise canceling headphones in a scene prior, then reference that scene when he is boasting. The noise cancellation works because the headphones are generating a pitch in the opposite wavelength as the sound the are canceling. But because it's creating and adjusting that pitch in real time, very adept listeners can hear a tiny high (very high) pitched whine when they put them on.
     
  14. Mic
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    He's a bit of a braggart because he excels at so much, but I really do want it to be at least grounded in some reality where it's at least possible for a human to do what he's claiming, even if it's spectacular.

    Would it be better to have him say he can detect sounds at 0.98 picowatts per square meter (the absolute threshold of hearing)? (It's okay if he sounds completely absurd to the layman, as long as what he's saying make scientific sense, hah.)
     
  15. GingerCoffee
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    That depends on your readers more than your character. Were I reading it, my brain would glaze over "0.98 picowatts per square meter". Keep your readers in mind as much as your character.
     
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  16. Mic
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    Thank you!
     
  17. Shadowfax
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    This may be off-topic, but I met a woman who had had to give up the flute because the minute deviations from perfect pitch caused her actual physical pain...I later found out (when my daughter was learning the flute) that this was a form of bragging, because a skilled flautist can vary the pitch being produced by adjusting the embouchure, so her pain was self-inflicted!
     
  18. Shadowfax
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    So a human can hear anything down to zero decibels, and anything lower doesn't exist? Isn't that like a tree falling in a forest when nobody is around? But what if a bear hears it? Does that count?
     
  19. SwampDog
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    Makes you wonder where the next theoretical limit will be.

    More quantum discoveries - temps below 0 Kelvin.
     
  20. Howard_B
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    Bragging about hearing wold normally be associated with high frequencies imho. have you heard about the anti teenager transmitters that some shops use ? they emit a high pitched squeak that only kids under about 20 can here and causes them to move away ?
     
  21. Jack Asher
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    Jack Asher Wildly experimental Contributor

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    Did you not read your own link? That's an average of many different atoms, some stopped and some not. It's a fucking math trick, like the fact that all American families have 2.51 kids.

    At zero decibels the atoms surrounding the sound source are not compressing. They are not rarefacting. The physical properties of sound are not happening. There's no way to go negative there. It's not a "theoretical limit", because contraction and rarefaction are positive quantities, it's impossible to have their movements be a negative factor.

    This is actually quite easy to solve. The compression and rarefaction of molecules takes place in that case, "sound" is the process by which the brain interprets that information. If no one is around to hear it, then sound cannot happen, even though the physical process by which sound is created has taken place.
     
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  22. SwampDog
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    I was merely addressing your aside on temperature, here:
    Nothing lower than 0 K, a bit like nothing faster than light. Theoretical limits until new discoveries are made. Did I read you wrong, somewhere?
     
  23. GingerCoffee
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    No, it's not like the limits of light speed. Seems like you might be missing the concept of what temperature is a measurement of and what 0.0 Kelvin means.

    Temperature is a measure of energy represented by the movement of molecules. How do you get negative motion?
    http://en.wikipedia.org/wiki/Kelvin
     
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  24. SwampDog
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    Thanks, @GingerCoffee . I always understood 0 K to be the point where all atomic activity stops - absolute zero. Several articles highlight gases forced to temperatures a few billionths of a degree below absolute zero i.e. a minus K figure. I was referring to temperature, not molecular activity, but I'll read up on it some more. Long time ago since I touched it.

    Cheers
     
  25. Jack Asher
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    Thanks @GingerCoffee, I knew you had my back on this one.
     

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