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Thread: Why do we hear in octaves?

  1. #1 Why do we hear in octaves? 
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    This question has been bugging me for a while:

    Why do we hear sound in octaves?

    I'm not particularly knowledgeable about the subject of sound, but to my (somewhat limited) conception of it, octaves should not exist in nature -- wavelength/frequency/period etc. simply increases or decreases, leading me to believe that we should hear all tones as something of a single chromatic scale, but we don't. We can hear tones repeating themselves at higher and lower pitches. I'm curious as to what factor of sound waves imposes this sensation in our brains.

    Any thoughts?


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  3. #2  
    Forum Cosmic Wizard spuriousmonkey's Avatar
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    I doubt we hear in octaves.


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    Many musical instruments and the human voice vibrating at the base frequency also contain overtones which are multiples of the base frequency; i.e., octave(s) up. Maybe that has something to do with it.
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  5. #4 Re: Why do we hear in octaves? 
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    Quote Originally Posted by Noobslayer
    This question has been bugging me for a while:

    Why do we hear sound in octaves?

    I'm not particularly knowledgeable about the subject of sound, but to my (somewhat limited) conception of it, octaves should not exist in nature -- wavelength/frequency/period etc. simply increases or decreases, leading me to believe that we should hear all tones as something of a single chromatic scale, but we don't. We can hear tones repeating themselves at higher and lower pitches. I'm curious as to what factor of sound waves imposes this sensation in our brains.

    Any thoughts?
    An octave interval represents a doubling of the frequency of a sound wave. It's a physical absolute rather than something we merely perceive. Different people have varying abilities to accurately judge frequency differences, or to replicate the interval themselves, but an octave is always an octave whether the person is capable of spotting it or not.
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    The pitch, why we hear an octave when the frequency doubles, is one interesting aspect. The other interesting aspect is the intensity. Why do we hear in decibels? You can read more on the lecture notes on hearing. Also, why are we more sensitive to certain pitches than others?

    Personally, I think it has to do with the anatomy of the ear and how it evolved. May be certain pitches mean danger and we evolved to be more sensitive to them. As for hearing in octaves, I'm not sure why or how that came about to be. Also, why do we hear certain combinations of notes very clashing while well known harmonics (like C major) feel very nice? or A minor feel very sad.

    Maybe an expert in physics/music wants to chime in...
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    Here's a web site that claims perception of octave equivalency was observed in monkeys.

    http://web.telia.com/~u57011259/eng7.htm
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    Noobslayer

    Quote Originally Posted by Harold14370
    Many musical instruments and the human voice vibrating at the base frequency also contain overtones which are multiples of the base frequency; i.e., octave(s) up. Maybe that has something to do with it.
    I suspect that Harold has the rights of it.

    Your basic octave is a doubled frequency (halved wavelength) and will therefore affect any resonant body (ear drum, hammer-anvil-stirrup etc) that is sensitive to the lower frequency (within limits, of course) and, to a certain extent, vice versa.

    But the other, more delicate point that Harold is making is that the octave (the Eight) is also composed of varying whole number ratios of the lower frequency.

    PEDANT ALERT: In the modern Well-tempered System the scale is no longer made up of simple ratios, but notes increasing in frequency (each 'semi-tone') by the twelfth root of 2. Traditionally, however, and by all accounts 'naturally', the scale is built on the simpler ratios 1:2, 2:3 and so on.

    These whole number ratios also, therefore, are more easily responded to by resonating bodies that are sensitive to the lower ratio. This, again, I believe, is a matter of physics.

    What evolution may well have done is take this naturally occurring sensitivity and exaggerate it in our perceptive systems so that we can take advantage of it in terms of:

    1) Increased audibility for communication (if one resonance does not get through the foliage maybe another will, but will still be recognisable as the same person/timbre)

    2) Increased scope for sexual selection (musicians always seem to get their groupies right?)

    And other possibilities that I'm not imaginative enough to think of right now.

    But, as I said, I believe it's the simple physics of resonance that makes the octave-based scale (and similar, more or less complex scales) the ones that humans use.
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    We are discussing a hypothesis as a fact. I still haven't seen any evidence we hear in octaves.

    In fact, a quick browsing of the scientific literature seems to confirm that the hearing range is continuous.

    Also the structure of the inner ear suggests a continuous hearing range.
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    Quote Originally Posted by spuriousmonkey
    We are discussing a hypothesis as a fact. I still haven't seen any evidence we hear in octaves.

    In fact, a quick browsing of the scientific literature seems to confirm that the hearing range is continuous.

    Also the structure of the inner ear suggests a continuous hearing range.
    I interpreted the question as 'why are we particularly attuned to sounds arranged in octaves', not 'why can we only hear in octaves', hence my response.
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    I think it is clear that we can hear any sound in a certain range, but since we humans love patterns, we specifically pick up on naturally occurring structure in sound waves. We then find it stimulating to throw together and listen to complex arrangements of such sounds, e.g. music, speech, etc.
    Disclaimer: I do not declare myself to be an expert on ANY subject. If I state something as fact that is obviously wrong, please don't hesitate to correct me. I welcome such corrections in an attempt to be as truthful and accurate as possible.

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    Quote Originally Posted by spuriousmonkey
    We are discussing a hypothesis as a fact. I still haven't seen any evidence we hear in octaves.
    I can hear an octave interval. It's very obvious to me. I don't have any musical training either. I know that it is the same note, so something in my brain has noted that the frequency has doubled or halved more or less exactly. The very design of sheet music and musical instruments reflects the fact that most humans perceive sound in octaves.

    Quote Originally Posted by spuriousmonkey
    In fact, a quick browsing of the scientific literature seems to confirm that the hearing range is continuous.

    Also the structure of the inner ear suggests a continuous hearing range.
    The ear is the receiving device, but does not interpret the signal. It's structure places limitations on the range of tones we can receive and the clarity and "resolution" with which they can be transmitted to our brains. The interpretation of the interval (and the signal analysis overall) is done by the auditory complex of the brain. It is that complex which recognises frequency doubling and interprets it as a transposed note.
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    I'm pretty sure octaves are a part of a musical language and can be related to science but we don't hear in octaves we hear in sound waves etc.

    Theres seven notes in the western octave (atleast i'm pretty sure it's called a Western octave...) but there's something like 27 in the Indian one. Octaves are part of the musical language we don't hear in them.
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    Quote Originally Posted by mathew0135
    I'm pretty sure octaves are a part of a musical language and can be related to science but we don't hear in octaves we hear in sound waves etc.

    Theres seven notes in the western octave (atleast i'm pretty sure it's called a Western octave...) but there's something like 27 in the Indian one. Octaves are part of the musical language we don't hear in them.
    I do. An octave sounds to me like the same note transposed up in pitch. My brain recognises the doubled frequency of the sound wave. As to the Indian classical music notation system, it uses octaves and arose independantly of western musical notation.
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    Quote Originally Posted by TheBiologista
    Quote Originally Posted by mathew0135
    I'm pretty sure octaves are a part of a musical language and can be related to science but we don't hear in octaves we hear in sound waves etc.

    Theres seven notes in the western octave (atleast i'm pretty sure it's called a Western octave...) but there's something like 27 in the Indian one. Octaves are part of the musical language we don't hear in them.
    I do. An octave sounds to me like the same note transposed up in pitch. My brain recognises the doubled frequency of the sound wave. As to the Indian classical music notation system, it uses octaves and arose independantly of western musical notation.
    That doesn't make any sense, you're brain recognises the note being transposed up an octave higher if you've learnt to hear that way but it still doesn't mean you hear in octaves.
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    Quote Originally Posted by mathew0135
    Quote Originally Posted by TheBiologista
    Quote Originally Posted by mathew0135
    I'm pretty sure octaves are a part of a musical language and can be related to science but we don't hear in octaves we hear in sound waves etc.

    Theres seven notes in the western octave (atleast i'm pretty sure it's called a Western octave...) but there's something like 27 in the Indian one. Octaves are part of the musical language we don't hear in them.
    I do. An octave sounds to me like the same note transposed up in pitch. My brain recognises the doubled frequency of the sound wave. As to the Indian classical music notation system, it uses octaves and arose independantly of western musical notation.
    That doesn't make any sense, you're brain recognises the note being transposed up an octave higher if you've learnt to hear that way but it still doesn't mean you hear in octaves.
    The gist of it is that your ear can detect anything with a certain frequency range, but our minds have developed towards "paying more attention" to certain frequencies and combinations of frequencies. This has almost certainly been shaped by the advent of language and music as a social bonding activity, certain sounds of nature that can be recognised faster as a predator or fire, thunder or whatever. Octaves form part of all of these, in that it provides an easily recognised structure required for use in communication and music. Our brains can almost certainly recognise the similarity between notes separated by octaves, while still recognising the difference. This adds further potential for use in a variety of applications as an easily recognised pattern. So TheBiologista's brain is probably geared to easily recognise octave instances, as are most other brains. So it does not mean that you hear in octaves, just as catching a ball doesn't mean your brain can do calculus behind the scenes. Anyway, I think most of these points were already made by others first, so there you have it.
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  17. #16  
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    Quote Originally Posted by mathew0135
    That doesn't make any sense, you're brain recognises the note being transposed up an octave higher if you've learnt to hear that way but it still doesn't mean you hear in octaves.
    It does make sense if you think about it. Let e try to explain it better. An octave is the name we apply to what we now know to be sound wave frequency doubling. Thus it is an interpretation of information. Our ears pick up sound waves and transmit that information to our brains. From the ear's point of view, no we don't "hear in octaves" since the ear has no interpretive function. It may transmit with varying degrees of fidelity, but that's about it.

    Hearing however, is not just the reception of sound but it's interpretation by the brain. It may sound rather like the old "tree falling in the woods" question, but what is "hearing" without a mind to hear?

    The brain of an average person, assuming they have been able to hear since brain formation, tends to interpret two tones separated by a doubled frequency as being the same note in differing octaves. This is called "octave equivalency" or "octave circularity". Were this trait not almost universal in humans, we would see quite disparate musical notation systems across the world. But we don't. Almost all musical systems, even separated by large geographical distances, are based on octaves. There are exceptions to the ability to interpret intervals, of course. Some people seem unable to make the distinction between all but the most extreme intervals, or may not recognise octaves at all. But these are not the norm. In fact octave equivalency is not only common in humans but has been observed in other primate species too. It is generally now accepted to be a "hard-wired", evolved characteristic.

    A rough summary with some primary research attached:
    http://web.telia.com/~u57011259/eng7.htm

    Quote Originally Posted by KALSTER
    So TheBiologista's brain is probably geared to easily recognise octave instances, as are most other brains. So it does not mean that you hear in octaves, just as catching a ball doesn't mean your brain can do calculus behind the scenes.
    The flaw in your point is that the brain does do complex calculations subconsciously to judge collisions, depth perception and all manner of similar problems.

    My core point is that "hearing" is the combination of ear and brain. The absence of either component renders the function non-existent.

    Edit: Oops, Harold already pointed us to that link above. It's good though.
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    Quote Originally Posted by TheBiologista
    Quote Originally Posted by KALSTER
    So TheBiologista's brain is probably geared to easily recognise octave instances, as are most other brains. So it does not mean that you hear in octaves, just as catching a ball doesn't mean your brain can do calculus behind the scenes.
    The flaw in your point is that the brain does do complex calculations subconsciously to judge collisions, depth perception and all manner of similar problems.

    My core point is that "hearing" is the combination of ear and brain. The absence of either component renders the function non-existent.
    My point was that it is more a learned feedback system than actual calculations going on. No?
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    I tried this myself with an electronic keyboard. I have zilch musical training.

    Play 2 notes an octave apart. Then play two notes that are an octave plus or minus one note. The octave sort of blends together but the octave plus or minus a note definitely sounds more like two different notes played together.

    I couldn't always tell an octave when played by someone else. Fifths sort of blend together too. But I think there probably is something there.
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    Quote Originally Posted by KALSTER
    Quote Originally Posted by TheBiologista
    Quote Originally Posted by KALSTER
    So TheBiologista's brain is probably geared to easily recognise octave instances, as are most other brains. So it does not mean that you hear in octaves, just as catching a ball doesn't mean your brain can do calculus behind the scenes.
    The flaw in your point is that the brain does do complex calculations subconsciously to judge collisions, depth perception and all manner of similar problems.

    My core point is that "hearing" is the combination of ear and brain. The absence of either component renders the function non-existent.
    My point was that it is more a learned feedback system than actual calculations going on. No?
    It can't be both? As far as I know, we do indeed learn to hear based on stimuli in infancy and that this works within the bounds of our genetics. The end result seems to typically be that we consistently end up developing octave equivalency. Those that do not are a relative minority. Thus we "hear in octaves".
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  21. #20 octave hearing 
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    Animals don't percieve music in the same way we do. Marvin minsky spent a long time on that subject as well. As he said, dogs don't tap their foot to a beat, and charned snakes in India are actually charmed more than by the movement of the flute and the music is redundant.
    Humans are special in many ways, we create concepts and do great CLUSTERING...
    On some islands where taxonists have been to, using analytical tools for assigning species in the differentiations between animals, they find roughly the same number of species as the naitves had names for. And classifying things like different birds from minute attributes is no easy task when there are hundreds.
    Humans do it naturally. It may appear wierd that a continuous spectrum of specific individual wavelengths/frequencies (assuming sound speed roughly constant),... will have groupings... Why?
    From the previous posts some responses skimmed over the concept that we hear in octaves because it is pleasant to do so. Structure learning and structure associations are an addiction to human brains. To see some structure and then to manipulate it in music is the next best thing to legos. 'this is bad' 'that is good' 'this goes well like this' etc. And babies love music too. There are lots of studies on babies learning from music, the mixtures of compatible to non-compatible musical structures assigns emotional intelligence.
    People go crazy in football games, why? Because we decided it so, it fits well. Pple like segmenting.
    And segementing notes as one note is twice the other one, is a decision which remains as simple to percieve as pleasant from a young age.
    How simple can things get?
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    People go crazy in football games, why? Because we decided it so, it fits well. Pple like segmenting.

    What a great thread.



    Finding patterns helps you survive. You don't see them, you die. You look too hard and see them when they aren't really there, you die. (Evoluationarilly speaking - so goes the idea).

    Paranoia - seeing patterns that aren't really there. Science? I'm sure there must be a difference.
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    Quote Originally Posted by Vexer
    Finding patterns helps you survive. You don't see them, you die. You look too hard and see them when they aren't really there, you die. (Evoluationarilly speaking - so goes the idea).
    Not exactly. The old anecdote goes something like this. You're a stone age man out on the savannah. You hear the grasses rustle in a distinctive way. You assume it's a lion and you make yourself scarce. It's slightly unreasonable pattern recognition. 9 times out of 10, it's just the wind. But 1 time out of 10, you die. Our minds have been selected over several million years in favour of assuming causal connections when they're probably not there. My addition to this is kinda speculation. This trait has also allowed us to resolve unresolvable questions that would plague our very curious minds out on that savannah. It's not much use trying to work out what makes the sun rise when you should be listening out for that rustle in the grass. So we invent causes. The sun is pulled by the sky chariot, and that's the end of the debate. Was that a lion?

    Quote Originally Posted by Vexer
    Paranoia - seeing patterns that aren't really there. Science? I'm sure there must be a difference.
    Of course. Science is an attempt to account for our capacity to fool ourselves. It's a philosophy that demands evidence of all things. That is rigorous in its approach to causality. Above all, it is designed to be competitive- we must always defend our ideas from others. And if our models fail to account for all observations, they're thrown out. Nothing is sacred anymore.
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    What you said is what I said: if “You look too hard and see them when they aren't really there” – enough – “then you die.”

    If you spend long enough hiding from the wind, you die. I said.


    But as for the next thing I said… given that all of Science is Wrong (technically), it’s all, technically, Paranoia. Science is instituted Paranoia. Another thread, perhaps.
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