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The White Noise of Smell 82

Frosty P. writes "Scientists have discovered a new smell, but you may have to go to a laboratory to experience it yourself. The smell is dubbed 'olfactory white,' because it is the nasal equivalent of white noise, researchers report in the journal Proceedings of the National Academy of Sciences. Just as white noise is a mixture of many different sound frequencies and white light is a mixture of many different wavelengths, olfactory white is a mixture of many different smells. In a series of experiments, they exposed participants to dozens of equally mixed smells, and what they discovered is that our brains treat smells as a single unit, not as a mixture of compounds to break down, analyze and put back together again."
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The White Noise of Smell

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  • by Trepidity ( 597 ) <delirium-slashdot.hackish@org> on Saturday November 24, 2012 @07:37PM (#42084027)

    White noise is actually not perceptually neutral noise. It's mathematically random noise, with a flat power spectrum, meaning that for example the sound energy between 25-75 Hz is the same as that between 15000-15050 Hz. But because the human ear's perceptual loudness curve is not flat, the perceptual frequency distribution of white noise is not actually flat. To produce perceptually neutral noise, you need to apply the inverse of the human ear's perceptual loudness curve to white noise, which results in grey noise [].

    But beyond that, it seems they actually mean something different, more like "perceived as indistinct background noise". That's a wider range of things, and has to do with being able to resolve specific, distracting components, not necessarily with mathematical definitions of noise.

    • I'm guessing they got it confused with white light, which the authors mention in the abstract. (And hey, what's a normalization curve between friends?) But you're right, a paper on perceptual physiology should not have made that glaring a mistake.
    • From the summary, I think they're talking about a random composition of smells. Perceptual neutrality is related to our brains ability to adjust to a shifting noise floor. As a Vermonter, I'm used to doing this with smell on an annual basis [].
    • by Anonymous Coward

      True grey noise would kill you. The 19999.9Hz component that's being amplified 10^20 times so you can hear it would blow up your head by mechanical action.

      • by Anonymous Coward

        True grey noise would kill you. The 19999.9Hz component that's being amplified 10^20 times so you can hear it would blow up your head by mechanical action.

        Assuming that you normalize the noise based on the 400Hz amplitude or whatever.
        If you use the 19999.9Hz as a reference and attenuate the rest of the frequencies from that to get grey noise it won't.

      • I don't know about you, but at 39 I can still hear 20kHz just fine.

        • I too am one of those males that has hearing extending above the normal human high range described as belonging to "children and some young women". I grew up hearing the scream of 17.5kHz flyback transformers in TV, but now it is the 20-25kHz ballast in more than half of the flourescent bulbs that annoys the hell out of me. I'm 48 years old

          • by Anonymous Coward

            You're quite possibly hearing harmonics rather than the fundamental tone. I can "hear" florescents too, but I can't hear anything above 16 KHz.

            • by Lumpy ( 12016 )

              How did you test this? If you used your computer speakers, then you did not hear it. very few speakers and computers can actually generate a clean tone above 16Khz.

              By using a real signal generator with frequency counter and a studio grade horn tweeter I found I have a roll off starting at 22Khz at the age of 45. I also discovered the tinnitus I have is at 15.53Khz and a reverse waveform will NOT eliminate it. I was hoping the mind would resolve the polarity of what it "hears" so I could use technol

            • Harmonics would be higher, not lower.

    • To produce perceptually neutral noise, you need to apply the inverse of the human ear's perceptual loudness curve to white noise, which results in grey noise

      For similar reasons, to produce a smell that perceptually blends out and obscures other smells, you would have to take into account the receptors of nose you want to obscure it from, and what molecules it's most sensitive to.

      This means "olfactory grey" would be different between species, possibly between individuals.

    • by Bobtree ( 105901 )

      Sound may be a better analogy than you realize. See []

  • Well, we all know what the brown noise of smell is.
  • by Jafafa Hots ( 580169 ) on Saturday November 24, 2012 @07:50PM (#42084087) Homepage Journal

    the amount of "white smell" if you use Dolby Nose Reduction.

    Personally I think analog smells are way more realistic than digital.

    • >

      Personally I think analog smells are way more realistic than digital.

      Well duh.

      Digital smell- You smell it or you don't

      • Well there is error-correction for reproducing the lost smell bits, but it tends to make everything smell like bacon.

    • the amount of "white smell" if you use Dolby Nose Reduction.

      Personally I think analog smells are way more realistic than digital.

      But you need vacuum tubes to properly reproduce it.

  • by Kargan ( 250092 ) on Saturday November 24, 2012 @08:26PM (#42084249) Homepage

    This is one of the differences between humans and animals, such as dogs, for instance. Dogs smell each component separately.

    This is why they make such good detectors for things like explosives or drugs -- they are still capable of pulling the "bomb" smell out of a complex mix of smells or when the smell is deliberately being masked, thanks in part to their highly adapted vomeronasal organ, also called the Jacobson's organ. []

    • If they smelled each chemical individually they wouldn't be able to identify people by smell, which they can. Their sense of smell works the same as ours. They just have better resolution and sensitivity.
      • by adolf ( 21054 )

        If they smelled each chemical individually they wouldn't be able to identify people by smell, which they can.

        This is non sequitur, to say the least.

        It is like saying "If they sorted the apples from the oranges individually they wouldn't be able to recognize a reindeer, which they can."

        In other words: It doesn't make sense.

        Please try again.

        • by jonadab ( 583620 )
          The other poster was assuming that the individual olfactory components of an individual person's smell (as distinct from other humans), on a per-compound basis, change from day to day.

          Admittedly, this is not common knowledge, so it would have been nice to see a citation -- but this is Slashdot, so sometimes we have to make some allowances.
      • []

        Sounds to me like they can smell each chemical individually.

      • by gl4ss ( 559668 )

        well, you read each letter individually.

        still you can recognize the words.

        • My point was that "dogs smell each component separately" appears completely unfounded. Dogs are extraordinarily good at detecting FAINT smells and identifying specific PATTERNS. That doesn't imply that they use a different METHOD of collecting and processing olfactory data.
    • by rikxik ( 1337017 )
      My python Monty has Jacobson's organ as well but people just aint as receptive!
    • Re: (Score:1, Troll)

      This is why they make such good detectors for things like explosives or drugs

      Oh really? I thought they made such good detectors because they can take cues from the body language of their trainers, thus validating a "hunch" and allowing an in for imaginary probable cause... I mean, an electronic chem sniffer would be far more accurate, thus inferior.

      Or, do you really believe that horses and dogs can do math?

    • Well this was just brought up in another thread, so I'll correct it again here. Dogs are terrible detectors for drugs, being wrong anywhere from 50% of the time to 85% of the time depending on the circumstances. []

      Although this is mainly attributable to them wanting to please their handler or picking up on the handlers body language. And personally I watched a dog search 32 jail cells once, it alerted in 8 of them, drugs
    • I'm curious now to know-- how many different odors can a (properly trained) human reliably identify when they are presented simultaneously? Like the parent poster, I'm pretty sure that the answer is more than "one". I also suspect that the answer depends on what combination of odor molecules is used. (E.g., perhaps we could identify three simultaneous odorants if they all belonged to different "genera"... floral, vinegary, and bitter... but maybe it would be harder if all three were floral.) Anyway, it

      • I'm not a professional chef, but I'm a competent cook. I can certainly pick out individual flavours to the extent that I've been able to reproduce, in one or two attempts, meals I've eaten at restaurants.

        Also (and I don't know where I heard/read this - inflight magazine?) it goes against the theory of perfume design, which is that it sort of works like a musical chord, with a bass, middle and top.

  • ... given that the function of smell in animals is to allow them to identify specific objects and substances.

    That's what the olfactory cortex is for: pattern recognition. It's a lot more useful to identify "smells like a wet dog" than have a report that lists all the chemical components of wetdogness in a list.

  • Hey (Score:3, Interesting)

    by Anonymous Coward on Saturday November 24, 2012 @09:20PM (#42084451)

    Speaking as someone with a seriously sensitive sense of smell... THE WORLD FUCKING STINKS!

    Every person is walking around in a cloud of their own personal products. Aftershave, cologne, perfume, FUCK that god dammed axe shit, body lotions, makeups, hairsprays, nail polishes, air fresheners, smoke residue, food residue and sooooooo many other nasty smells because honestly most of you are not very dammed clean either. And you just try to cover that up.

    And i call bullshit on this article. I can pick out individual smells in those massive clouds. And i don't like it. The natural world smells ok. Very low key. But the human world? Jebus wept...

    Unfortunatly there doesn't seem to be an upside to this. Theres no job for human drug dog. Altho i suppose i won't ever accidentally eat bad food. Or die in a gas leak.

    • Speaking as an Anosmiac, the world *stills* fucking stinks... only I can't use my nose to avoid the stink...

      Count your blessings bro/sis because you have never experienced the other eating habits are a total mess because what seems perfectly normal and delectable to others feels absolutely disgusting to eat for me... I never know when I am danger of gas leaks, and I have sat still with the gas leaking, only for a relative to come in and start a panic. My dreams of chemistry education dashed becaus

    • by sjames ( 1099 )

      Hear Hear!

      The worst part is that the 'perfumes' they put in so many products smells FAR worse than the natural smell of the product. The artificial 'floral scents' smell NOTHING like the actual flowers to me. I can't even guess which flower they're supposed to smell like.

      • Well, I've got to agree with you on that one. I once bought scented bog roll by mistake, I'll fuck the pope if it didn't smell better after it was used.

        And have you ever tried Axe deodorant? They seem to change the range twice a week but there's always one that does time travel; spray it on and you smell exactly like you would in eight hours if you didn't put any on at all.

        • by sjames ( 1099 )

          I can believe it. I avoid Axe just based on the smell as I approach it. I just use alum since it has no appreciable small.

      • by Uzuri ( 906298 )

        This this this.

        And what's the deal with scenting cat litter? First it reeks of that fake "scent", then it reeks of cat pee + the fake scent. This is not an improvement over straight cat pee.

    • I agree with you. My sense of smell is extremely sensitive. Being around people in a social situation is a horrible experience. The chemicals people use to mask their smells are worse than what they're trying to cover up. Simple pure clean is much preferred, though that doesn't last long.

      To me odors have texture and color. They can be smooth, rough, dusty, soft, bright yellow, dull red, etc..
      • by jonadab ( 583620 )
        I can see how odors might be described as having texture, in the loose sense of the word "texture". The timbre of sounds could also be described this way. A "smooth" sound might have relatively little variation in pitch from microsecond to microsecond and relatively few or relatively harmonically compatible frequencies at any given instant. A "rough" sound in contrast might have rapidly shifting and/or dissonant overtones and undertones. Something similar (albeit probably not time-based) could be said o
    • Just eat beans and cabbage to fight against people that are overly perfumed or reek of stale cigarettes. Everybody loves the smell of their own farts, so walking around in a cloud of it should make you happy.

  • by cervesaebraciator ( 2352888 ) on Saturday November 24, 2012 @10:22PM (#42084687)

    Just trying to understand how others experience the world, so please forgive me if I ask an obtuse question. I watched a video [] the other day which had been described by some with Asperger's as a very accurate depiction of their experience of a meltdown. What I noticed from the video, above all, was the way things that would have blended together as white noise for me demanded constant attention, as much as I wanted to ignore them.

    So my question is this: if what I took from the video was in anyway accurate (if not, just let me know), does anything analogous happen with smells as well? I.e. as individual sights and sounds do not equalize to manageable or meaningful levels, do smells also each cry out for individual attention?

  • by PPH ( 736903 ) on Saturday November 24, 2012 @10:52PM (#42084815)

    Also known as "locker room".

    • Vanilla isn't plain. IMO.

      • by jonadab ( 583620 )
        Most Americans perceive vanilla as plain, because as a rule vanilla products here have exactly the same amount of vanilla in them as other products. A white cake may have a teaspoon of vanilla in it. A chocolate cake will have a teaspoon of vanilla in it plus a quarter cup or more of cocoa powder. A carrot cake will also have a teaspoon of vanilla, plus carrot shavings and an assortment of spices. Similarly, vanilla icing has the same amount of vanilla in it as chocolate icing or strawberry icing or min
  • by Anonymous Coward

    This reminds me of something I've been wondering about for a while: is there a way to digitize smells, or otherwise come up with a baseline of communicating smells between people? If I want to show a friend something visible, I take a picture. If I want him to hear it, I make a recording. How do I do that for an odor? Is that even possible?

  • when walking into a bath and body works, or yankee candle store.

  • by Lumpy ( 12016 ) on Sunday November 25, 2012 @02:45PM (#42088289) Homepage

    Will "white nose" smell cause a bloodhound to not be able to follow the scent? This may be the holy grail of hunter scent masking.

  • tested by Prof Farnsworth's Smell-O-Scope.
  • If i can only discern 1 smell at a time, as one mix of a smell, i would not be able to tell you have BO AND use old spice could I?

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