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Psychoacoustics - what is it and why does it matter?

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  • Psychoacoustics - what is it and why does it matter?

    This new section of the Harbeth Knowlwedge Archive looks at psychacoustics, meaning the way the human ear and brain perceive sound and interpret it.

    Our entire auditory system developed not for listening to music or even speech, but to make us aware of our environment and specifically, predators in close proximity. In fact, in evolutionary terrms, music is a complete irrelevance, as it appeared only about 35,000 years ago.

    I am not an expert on the hearing system, but even a rudimentary appreciation of how we hear is absolutely essential to be able to understand and intrpret why we like some sounds, and not others. And above all, to caution us about making irrational, emotional decisions when purchasig audio equipment because we've allowed (or encouraged) our ears to be seduced by our hearts and overrule our brain. In my opinion, audio should never be critically evaluated with the eyes open; a blindfold is essential. Failing that, look at the floor in the middle distance, but never at the equipment.

    Some links: Overview here

    This thread is in the objective, knowledge-tree part of the HUG. I welcome objective posts that further illuminate this fascinating and complex subject and draw on published research or professional experience. This is an important subject, and is Moderated.
    Alan A. Shaw
    Designer, owner
    Harbeth Audio UK

  • #2
    National Geographic "The Musical Brain"

    I now remember the name of the documentary about musicians' brains. It's a Canadian TV production for National Geographic and its called "The Musical Brain" looking at the work by Dr. Daniel Levitin of McGill University. He has also written 2 books called "This is your brain on Music" and "The World in Six Songs".

    The documentary features amongst others Sting, Michael Buble and Feist, exploring music, creativity and the mind. Very interesting as it also looks at brain activity under an MRI during listening, creative and imaginative phases of Sting’s brain.

    Comment


    • #3
      Hearing and perception

      We used to have a sub category under "Hearing and Perception" where I posted a few link regarding recent progress made in understanding our auditory system. The category isn't visible any longer. Would discussion contained be relevant to this topic?

      ST

      {Moderator's comment: seems some threads have (temporarily?) vanished during relocation ... }

      Comment


      • #4
        The brain and its fallability

        I think too that the brain hears what it wants to hear. To wit, better sound after an exotic component is dropped into the system. Ears are just transducers after all, it is the brain that hears at the end of the day. So if I know from reviews that the exotic adds an extra dimension to the sound, I end up hearing it. Particularly if I have also paid fancy money for it.

        Given this, the effect of alcohol on the brain must also be the reason why the system sounds a lot better to me after moderate imbibing. Turning the lights down low is another useful audio tweak!

        Which brings me to the famous glow of tube amps. I wonder how the music would sound with a powered up tube amp in the component rack, even if it wasn't connect to anything. It wouldn't fool the person that has set it up, since he or she would know the situation. But I am pretty sure it would fool a lot of audiophile visitors into gushing over the liquid warmth of tube sound:-)

        Comment


        • #5
          Surviving in a fantasy ...

          The importance of recognising that the brain predominates in the perception of sound, rather than we just receiving pure sound, is hard to exaggerate; we filter it, process it, habituate to its quality, and learn to focus on aspects of it to the almost complete exclusion of all others.

          The ear, as Alan says evolved in a survival context, very much unconcerned with music, with the minor exception that I believe music evolved before speech; one can imagine the use of music as an inter-tribal communication form. (War drums).
          Dr Oskar Heil did much work in evaluating the sensitivities of the ear, and came to the conclusion that its main sensitivity was to transient sounds and not to the relative intensity of different frequencies, and he developed a tweeter with a good transient response as a result.

          I think that our brains, metaphorically like very powerful computers, apply massive amounts of processing to sound, these dependant on contextual objectives in differing environments, and this process is never free from the psychosocial needs, political pressure, and the aesthetic considerations of the individual.

          Personally I find a day at a Hi-Fi show exhausting, and a listening session with a dealer more so because of the perceptions of his work load in changing equipments, and pressure to buy.

          To me a very difficult and often ignored factor in listening to music on Hi-Fi, is that evaluation of Hi-Fi requires the scientific objectivist evaluative approach, but the musical medium, which we so often use to do such is one of the most emotional mediums there is.

          This is in my experience compounded by the excitement I have experienced, and with which I have also seen others overcome, when a much loved piece of music is played in a way which seems more revealing. It may occasionally be so, but I think that often a change in frequency response can be found to be responsible for emphasis of a particular instrument, and hence it is perceived more clearly and separately. Kumar Kane's comment about the brain hearing what it wants to hear regrettably can, I feel, be extended very widely to much perception; often people perceive only that which they wish to, they being more than happy to reside in fantasy, this being described by psychologists as a survival strategy.

          Comment


          • #6
            Frozen in time?!

            Very interesting post. You mentioned a few things that I have observed too.*

            I am not so sure about perception when we judge sound. At least it wasn't *the case when I first heard Harbeth singing. It was a Compact7 which looked so old styled and frozen in time. I think I didn't wait for the track to finish to recognize its quality. That's the first time i heard the name Harbeth. It is possible that we can chose not to hear what we don't want to recognize, IMO.*

            Could you explain what you mean by :-

            To me a very difficult and often ignored factor in listening to music on Hi-Fi, is that evaluation of Hi-Fi requires the scientific objectivist evaluative approach, but the musical medium, which we so often use to do such is one of the most emotional mediums there is.*
            Btw, it is probably true that we are preprogrammed to appreciated music long before we learn to speak.

            Comment


            • #7
              The surgeon and the sound enthusiast

              I think that the technical/scientifc/evaluative, and the receptive/emotive artistic aspects of the pursuit of Hi-Fi as an interest, are entiely different paradigms, and care has to be taken, and discipline applied, to avoid confusing them. We all by now know about the objective/subjective divide, originating I believe in the 80s.

              To evaluate Hi-Fi we use certain well established technical criteria which show a correlation between their increase or decrease, and that also of the percieved sound quality, though there are many more to be discovered I suspect.

              I have with many friends/colleagues strained over the years to try to screen/filter out the pleasurable/artistic response, which probably occuring at a 'lower' level of the brain, perhaps towards the limbic system, and to perceive purely the tonal changes due to a modification or change in equipment whilst also bearing in mind the established technical criteria. This struggles reflects the fact that music at its best can send one into raptures of enjoyment, but in each of these states of receptivity, I think that the brain is in a very different configuration or mode.

              I know it may be a rather crude analogy, but one may be a motor enthusiast, and tune up/modify or tweek one's vehicle, and subsequently take it for a test drive. Whilst sweeping through the beautiful country passing through gloriously green and browning Autumn foliage, one has to deliberately focus on the sound of the engine, or feel of the gear stick in an effort to observe any improvement resulting from one's work. I believe music to be the greatest of the arts, it providing me with enormous pleasure, this making only harder the struggle invoved to be in the 'objectivist' mode.

              We all in life have to screen out things and focus on the specifics we are trying to affect, but in this case, when the thing we are trying to screen out is so enamouringly pleasurable and potentially overpowering, it is I think harder. Another analogy has just occured to me.

              Imagine being a top breast surgeon at a Harley St. clinic, and being presented with an already very beautiful woman who is requiring an improvement to her breasts. The surgeon has to remain very filtered about his task, ignore his own personal reactions to her, and pay attention to the technical aspects of his work, the resulting aesthetics of it, and how she feels about his intentions.

              With regard to your case when you "first heard Harbeth singing", I have also come to the conclusion that the division between two brain modes or functions is not always clear. After a modification I listen concsiously to evaluate the results, but do not always appreciate them fully in so doing. Then, whilst in a less conscious state, not in intense focus, I often hear other improvements not noticed when trying so to do, and also, an improvement can 'slap one in the face' with its substantialness, as though 'caught of guard'.

              I have over the last few years come to the conclusion that there are for me two criteria which mark a genuine improvement in sound quality; hearing things never heard before on well know music, and, the removal of general mushioness, clutter and din, this latter often revealing just how flakey and amateur a perfomance is. I recently heard an old 'Stones track, and was amazed at how 'clunky' and amateur it sounded.

              Comment


              • #8
                Getting under the skin

                Originally posted by Pharos View Post
                ...Imagine being a top breast surgeon at a Harley St. clinic, and being presented with an already very beautiful woman who is requiring an improvement to her breasts. The surgeon has to remain very filtered about his task, ignore his own personal reactions to her, and pay attention to the technical aspects of his work, the resulting aesthetics of it, and how she feels about his intentions....
                Two good analogies.

                Regarding the surgeon and (female) cosmetic surgery, it is one matter for the woman to be self-motivated to seek out the scalpel, but quite another to feel peer pressuriesed into taking action. What I strongly object to is to the extreme language (which is to my mind so obvioulsy tongue in cheek) we read in the media and on fringe forums celebrating this or that new height in audio when the reality is that of extremely small incremental steps over a generation. This constant bombarding of the vulnerable (female) with ideas of inadequacy are precisely the same tricks used in many industries - including this - and miss the point entirely. A beautiful person has nothing to do with external appearance* and the appreciation of music can be greatly enjoyed on a portable radio.

                *Just a few nights ago, in the UK TV series "Beauty and the beast, the ugly face of prejudice" we were introduced to a London narcisist and the terribly disfigured Regie Bibbs from Houston. As my wife and I watched and Regie's quiet personality revealed itself, we ceased to focus on his appearance and became completely beguiled by his normality. Self evidently, under that misfortune, Regie is a truly beautiful man with a deep care for others. The outcome of the programme was most unexpected and refreshing.

                The analogy between the body beautiful (or not) and high-end audio was striking indeed. Look under the skin - be sensitive to whatever is motivating you. Reject the shallow.
                Alan A. Shaw
                Designer, owner
                Harbeth Audio UK

                Comment


                • #9
                  Group sociology

                  I agree entirely about the miniscule, if any, progress in audio reproduction, and have discussed with friends, the use of changing appearances throughout the 80s to the present with; shiny cones, frame finishes obviously aimed at th eye rather than function, excessive use of gold, twee mouldings which add nothing to function, and very excessively elaborate cable structures and finishes etc. Audio jewellery.

                  The real improvements are small, and I liken the changes to the process of traveling up a helical spring; if we are not careful we go round and round in accordance with the latest fashion, this seeming to me in many walks of life to be based only on the idea that we have found a new truth, but in reality the vertical assent, (real progress), if any, is very small. We have had in my audio interest, numerous swings towards each of the bass loading techniques, illustrated by manufacturers each producing models following this new trend.

                  The pressure to conform seems ubiquitously used in capitalism, and the pressure to change and aquire a new technology obviously promotes sales, and hence the profits of manufacturers. Group sociology does much to ensure compliance of the individual, as discovered by Soloman Asche in the 40s or 50s, and if a hen with a white head feather is placed in a coop with a hundred others with red ones, they will peck it to death.

                  I do however think that physical beauty can be part of person's beauty, but it is only one aspect of them and it is given by nature, not aquired by personal endeavour. I too watched the programme, and found the end refreshing, but I wondered how sincere the narcisist was. Yes, reject the facile, the easy, and work towards producing the substantive and ultimately more sutainable and rewarding.

                  Regarding the apparent emphasis currently on superficial 'beauty', I am reminded of a song by Al Stuart from "Modern Times" entitled "I really don't believe what's going on"; Group"She walks like Greta Garbo, and talks like Yogi Bear".

                  Comment


                  • #10
                    The substantive

                    Originally posted by Pharos View Post
                    ...Yes, reject the facile, the easy, and work towards producing the substantive and ultimately more sutainable and rewarding...
                    Very succinct. That sums up what we strive for at Harbeth.
                    Alan A. Shaw
                    Designer, owner
                    Harbeth Audio UK

                    Comment


                    • #11
                      Psychology and perception

                      Human perception is the most difficult thing to norm out.

                      I have a high school friend of mine that is now a researcher in Cognitive Science - and does research in the "familiar/unfamiliar" processing - indicated last time we chatted about his research he indicated to me that the brain appears to be a pattern processor first and foremost - and in things that are familiar (his work is visual not auditory so take it with the grain of salt) the brain spends less time processing new sensory data - but actually spends most of the energy on memory. ( papers )

                      If applicable (big "if") to auditory stimulation - this might imply that you don't really listen to music if it is familiar to you - but use the pattern of it to recall a memory that is what you really "hear" - this would cast a shadow over A/B testing in general unless this phenomenon were worked out. Might also mean only an unfamiliar piece of music is workable - or perhaps the experience is so wholly subjective it is impossible to norm it out scientifically? Or we are such pattern beasts we might completely miss over a gross tonality difference with an A/B switch?

                      I am making no such claims myself - but I am throwing out the idea for discussion that the psychological portion of perception may be important enough that we have to figure out a way to norm that away before we can truly trust our testing due to the way we process sound? It is a mystery to me why in isolation differences can seem plain as day, but in an A/B test it is exceedingly difficult to do so! Can we really have a truly universally applicable "objective" test when so much is "in your head?"

                      Food for thought, anyway - I will caution everyone that "I have no dog in this fight" - a long time ago I realized that for me that the whole thing is an aesthetic experience - and as such fundamentally subjective and beyond anyone's judgement except mine own. And when I feel transported to a live show or into the studio as much as possible, that's my metric.

                      Comment


                      • #12
                        The sensory jolt on A-B switch-over ...

                        Originally posted by Bromo33333 View Post
                        .... that the brain appears to be a pattern processor first and foremost - and in things that are familiar (his work is visual not auditory so take it with the grain of salt) the brain spends less time processing new sensory data - but actually spends most of the energy on memory. ( papers )

                        If applicable (big "if") to auditory stimulation - this might imply that you don't really listen to music if it is familiar to you - but use the pattern of it to recall a memory that is what you really "hear" - this would cast a shadow over A/B testing in general ...
                        Again, A-B testing is designed to highlight the sonic difference between A and B at the instant of switch-over and this it does extremely well. Are you saying that if I presented you with a slide show of two pictures of family members that you were familiar with but one picture had a colour cast that you wouldn't be able to recognise it on switch-over? Of course you would: the instantaneous comparison would jolt your brain into appreciating the differences. It's exactly the same with A-B audio testing - shown on a video clip here just recently.

                        Conversely, if the slide show image A transitioned (faded) progressively into the B image over a period of minutes as you watched, do you think you would suddenly say at any one point 'wow, that family member seems to have green skin'? I don't think so. Your visual/audio memory is not designed to make long-range comparisons; there is no evolutionary benefit for that behaviour. Our senses are designed to produce snap conclusions, side by side comparisons, better/worse, yes/no, pass/fail, go/no-go, danger/safe, attractive/unattractive, loud/soft, bitter/sweet, hot/cold ....
                        Alan A. Shaw
                        Designer, owner
                        Harbeth Audio UK

                        Comment


                        • #13
                          Tuning our senses?

                          Originally posted by Bromo33333 View Post
                          Human perception is the most difficult thing to norm out.
                          If applicable (big "if") to auditory stimulation - this might imply that you don't really listen to music if it is familiar to you - but use the pattern of it to recall a memory that is what you really "hear" - this would cast a shadow over A/B testing in general unless this phenomenon were worked out. Might also mean only an unfamiliar piece of music is workable - or perhaps the experience is so wholly subjective it is impossible to norm it out scientifically? Or we are such pattern beasts we might completely miss over a gross tonality difference with an A/B switch?
                          I suspect that this is one of those cases where the devil is in the detail of what is done in the auditory experiment. On the one hand we have an effect whereby what is perceived by the higher faculties of the mind is modulated by memory; on the other hand we have the fact that many of the senses are “tuned” to detect change. (If we look elsewhere in the animal kingdom, it is not hard to find examples of vision that are poor in terms of absolute acuity but extremely good at detecting movement).

                          One might hypothesize that the first effect (memory) might mask the second effect (change detection) by arguing that what is perceived by the mind is (mostly) the content of memory pointed to by the auditory sensation. But equally one might hypothesize that our ability to detect change in sensory stimuli might actually be enhanced when the auditory input is familiar; it is not inconceivable that evolution might have tuned our senses to detect changes occurring in our most familiar surroundings.

                          For a pair of hypotheses like these the test is, of course, experiment. Informally, an A-B test (with instant switchover) using passages of music of varying familiarity to the listener would seem to be appropriate. Of course, one would have to quantify the notion of familiarity so that one could use this in a statistical model of the outcome. But, appropriately modelled (and with big enough sample size to do this!) one could determine the functional relationship between familiarity and ability to detect difference.

                          Since the mind is so amenable to suggestion, it is not hard to think of a sequence of variations on such an experiment. For example:

                          1) The subject is played a 30 second excerpt of music in which there is a “transition” at a random location in the music. Afterwards the subject is asked whether they detected a change.
                          2) The subject is told that they are about to listen to a piece of music that includes a “transition” somewhere and are asked afterwards whether they noticed it.
                          3) The subject is told that they are about to listen to a piece of music that includes a “transition” at the twenty second mark and are asked afterwards whether they noticed it.

                          Of course, the subject is randomly assigned to a piece of music that either has or does not have such a transition. Each of these variations is asking a subtly different question to do with how the initial state of mind affects the process of perception.

                          Comment


                          • #14
                            Life changing A-B comparisons?

                            Originally posted by Simon View Post
                            I suspect that this is one of those cases where the devil is in the detail of what is done in the auditory experiment. On the one hand we have an effect whereby what is perceived by the higher faculties of the mind is modulated by memory; on the other hand we have the fact that many of the senses are “tuned” to detect change. (If we look elsewhere in the animal kingdom, it is not hard to find examples of vision that are poor in terms of absolute acuity but extremely good at detecting movement).

                            One might hypothesize that the first effect (memory) might mask the second effect (change detection) by arguing that what is perceived by the mind is (mostly) the content of memory pointed to by the auditory sensation. But equally one might hypothesize that our ability to detect change in sensory stimuli might actually be enhanced when the auditory input is familiar; it is not inconceivable that evolution might have tuned our senses to detect changes occurring in our most familiar surroundings....
                            I think that it's valuable to discuss and refine and explore the academic approach to the listening process as applied to audio equipment evaluation. But we mustn't lose sight of the fact that virtually no one who puts pen to paper - particularly those doubters of the validity of the A-B process - have actually tried it for themselves. That is, put themselves in front of two pieces of equipment (speakers, electronics, accessories - whatever), taken care to equalise the levels so they are certainly playing A and B at the same loudness (by far the most influential variable), and controlling the switch-over mechanism themselves to experience A juxtaposed against B with just a tiny fraction of a second gap as the relays change over.

                            Actually putting oneself into that hot seat is a possibly a life changing experience. It was for me 30 years ago. A rationalist would surely admit that it is simply not valid to continue along the exclusively subjectivist path if before the A-B switchover the listener held (as so many do) rock solid, unshakeable, 'swear on my grannies life', 'cross my heart...' opinions of marked differences between A and B, but after actually taking the test is neither able to hear any differences at all or is unable to state a preference for one or the other or is even unable to positively identify A or B on more than the 50/50 occasions you'd expect by throwing a dice. If the listener refused to accept what he heard for himself in the A-B comparison and reverted to his former preconception (as the majority would) then that tells much about human nature and nothing about the construction of the test.

                            The reason the audio industry is in the deep rut it is is because the good products and the bad ones are presented side by side in the market, looking equally credible to the non-technical consumer. This does the consumer no favours. It stifles R&D investment and hence true progress. The audiophile industry is a law court where entirely innocent, decent upright defendants are daily found wrongly guilty and where flamboyant and more media savvy defendants are let of the hook or even lauded. We in the gallery know the truth about A v. B and shout out 'you've got it wrong - you've picked the wrong man yet again' but are powerless bystanders, drowned out by the howling of the public. Who can stand against the Law of Subjectivism prevailing at the audio court?

                            As the judge might say 'don't trouble me with the facts .... I've already made up my mind'. Simple, $20 A-B relay comparators are exceptionally valuable for getting to the facts of the comparative performance of A v. B.
                            Alan A. Shaw
                            Designer, owner
                            Harbeth Audio UK

                            Comment


                            • #15
                              ... and it's not only one person's opinion or one event which matters!

                              Scientifically and mathematically, fortunately or unfortunately depending on which side one is on, it takes more than one person's opinion or event/s to make a choice statistically significant. Who is one Mr. X to say that product A is superior over product B (and on what basis)? Trial and event wise, under no pressure, insignificant perceived differences WILL draw closer to 50/50 likelihoods, some quite obviously even after a very small number of trials.

                              It takes conviction (and bravery) for one person to say there is less difference than more.

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