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Since its inception ten years ago, the Harbeth User Group's ambition has been to create a lasting knowledge archive. Knowledge is based on facts and observations. Knowledge is timeless. Knowledge is human independent and replicatable. However, we live in new world where thanks to social media, 'facts' have become flexible and personal. HUG operates in that real world.

HUG has two approaches to contributor's Posts. If you have, like us, a scientific mind and are curious about how the ear works, how it can lead us to make the right - and wrong - decisions, and about the technical ins and outs of audio equipment, how it's designed and what choices the designer makes, then the factual area of HUG is for you. The objective methods of comparing audio equipment under controlled conditions has been thoroughly examined here on HUG and elsewhere and can be easily understood and tried with negligible technical knowledge.

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Frequencies, sound waves and hearing

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  • Frequencies, sound waves and hearing

    I will admit that I am not scientifically minded, but I have been reading many of the threads here on the Forum since I purchased my Harbeths and have begun to learn much about sound, acoustics, and how and what to listen for. As a little knowledge may be a dangerous thing, I have begin to wonder about whether sound waves can be changed - lowered or raised frequencies- after they reflect from a surface? Does a surface reflect the sound wave back at the same frequency, and cause new and different sound waves due to exciting the molecules of the object, or does the surface actually change the frequency of the incoming wave?

    I am curious about this due to the "discussions" that occur on various web forums between the digital crowd and the vinyl gang as to what sounds better...[From my perspective, I tend generally to listen to vinyl and have digital on in the background, however, if I do not have some music on vinyl, I will certainly sit and listen to it]. Vinylites will argue that there is more sound while digitalites will dismiss them as ludites. As there is more sound on vinyl up to 100khz as opposed to 20khz in digital that may seem correct, however if I understand it correctly, all of that sound above the 20khz is outside the range of most human hearing ability, thus logically there should be no difference between the two mediums...and the reason for my question (There are also arguments on getting a vinyl sound from digital theough all sorts of ways but that is for another thread).

    If the sound wave frequency can change there would be more sound in the room from vinyl than from digital assuming that the room has been treated acoustically and thus the sound is good, and if not vinyl guys are making up the "more sound" argument. Sorry for the long winded commentary but as noted, a science mind I was not graced with.

    Cheers

    George

    ps do we physically feel sound even if we cannot hear it?

  • #2
    Wave reflections

    ...Does a surface reflect the sound wave back at the same frequency...
    Yes, I believe so. I don't believe surfaces can change the wavelength of a sound wave in the same way as iridescence changes the wavelength of reflected light.

    However, surfaces can and do reflect frequencies by varying degrees. And since sound is rarely made of simple, single frequencies, certain frequencies in reflected sound will be suppressed and others enhanced. Thus the reflected sound sounds different from the original.
    Ben from UK. Harbeth Super HL5 owner.

    Comment


    • #3
      Sound waves ... and bombs

      Originally posted by Macjager View Post
      ... I have begin to wonder about whether sound waves can be changed - lowered or raised frequencies- after they reflect from a surface? Does a surface reflect the sound wave back at the same frequency, and cause new and different sound waves ...ps do we physically feel sound even if we cannot hear it?
      You've raised enough question in this one post to keep us busy for days! But just to look at the first and last.

      The fundamental property of a sound wave is its frequency. By that we mean the cyclic or rhythmic repetition of an event that gives it a rolling predictability that we call a wave. (If this cyclic predictability is absent then we can't talk about waves - we will just have a 'noise').

      Let's imagine we are standing on a beach on a windy day looking out to sea. We'd notice that there was a certain periodicity to the waves as they arrived and rolled up the beach. This predictability is so evident that if we didn't want to get our feet wet we could (hopefully!) anticipate their frequency and escape just in time. And where do the waves come from? It's a combination of the gravitational pull of the moon dragging the huge mass of the oceans upwards, the wind generated by the spinning of the earth's atmosphere, tidal flow etc.. Providing that the moon remains at the same distance, the earth spins at the same rate and the sun shines as brightly (heating the earth) the frequency of those waves will be the same in 1000 years as they were 1000 years ago. That's because the conditions remain the same and hence the same amount of energy is creating the waves.

      But imagine all those energy-input factors remain constant - how could we change the periodicity of frequency of waves arriving at the beach? We could replace the oceans H20 water with .... treacle. In other words, if we change the density of the medium we could (I assume) change the frequency of the waves. And the same must apply to sound waves. In air, at ground level, anywhere on earth, at a given temperature, air has a certain thickness or density. The sound wave does not know that it is being generated in your living room or in a Brazilian forest - it just 'is'. And it recedes from the source at a velocity which depends on temperature, pressure and density. Assuming these remain constant as it recedes, then the frequency must remain the same. But if we make a dramatic change in the density (you will your room from top to bottom with treacle) then yes, we could well change the frequency. But as that's not going to happen soon, I think we can say with confidence, that there is no likely mechanism in the real day to day world that is going to cause one frequency to morph into another.

      Indeed, if that was a concern then fixed musical pitch would be impossible and speech communication could be garbled. So you can definitely discount this worry. There is 100% predictability about frequency (given fixed temperature, pressure and density) everywhere and everywhere on earth where those three factors are fixed.

      As to 'do we feel sound' we most certainly do, but only at the very lowest frequencies (perhaps below 20Hz, in the sub-audio band), notes generated by the very longest and biggest organ pipes. And yes, our organs will resonate at those frequencies, and yes, if enough energy is applied, that LF sound will kill us. That is one characteristic of a bomb: the shock wave alone can kill from the inside even though externally we may look OK. (This also happens in car accidents).
      Alan A. Shaw
      Designer, owner
      Harbeth Audio UK

      Comment


      • #4
        Vinyl - a composer's nightmare?

        Originally posted by Macjager View Post
        ...I am curious about this due to the "discussions" that occur on various web forums between the digital crowd and the vinyl gang ... Vinylites will argue that there is more sound while digitalites will dismiss them as ludites. As there is more sound on vinyl up to 100khz as opposed to 20khz in digital that may seem correct, however if I understand it correctly, all of that sound above the 20khz is outside the range of most human hearing ability, thus logically there should be no difference between the two mediums.
        OK, we have covered this vinyl-v-digital debate here before (anyone find the links? I remember an LP groove photo).

        You mention the (theoretically) wider frequency response of vinyl as being the defining characteristic of its claimed superiority* by those 'vinylites'. But have you considered that that is only one of the characteristics of any reproduction system or media what has to be considered before a valid conclusion can be arrived at as to its acoustic merit? Picking on one - and in fact the only one - that is theoretically superior in vinyl - is a convenient bending of the truth, which is that in all other technical parameters, vinyl falls far short of digital.

        To honestly assess any medium we'd need to look at:
        1. Distortion; type, quantity and how related to replay loudness
        2. Noise; background and how related to replay loudness
        3. Channel separation
        4. Dynamic range; the maximum loudness envelope between the loudest possible sound and the quietest sound below which all other sounds are masked by hiss, crackles etc.
        5. Storage and durability and degradation with time and handling
        6. Repeatability; could identical 'pressing' duplicates be made year after year?
        7. Compression; how much if any is needed to ensure that the consumer's equipment can actually reproduce the dynamics and frequencies of the original master tape (makers can't assume any consumers have studio-grade audiophile equipment)
        8. Playing length per 'side'
        9. Susceptibility to impulse noise; scratch resistance
        10. Frequency response

        It's rather obvious to anyone at the recording end of the process that for points1-9 (and in practice 1-10) that digital reproduction is technically superior by a very big margin. Despite that, many listeners - me occasionally included - can enjoy listening to vinyl. But if we're honest, for 'emotional reasons' concerned with the performance of playing vinyl not for an technically justifiable reasons.

        One thing that absolutely must be remembered is that from the first second to the last on an LP side, there are clicks, scratches, grumbles, ticks, random noise due to the molecules in the vinyl compound and mechanical groove tracing distortions. Due to the way that music masks those when it is playing don't kid yourself into believing that it is only in the fade-out and run in/out grooves that those nasties are present. They are they are there continuously right under the music; you just don't detect them until the music level drops when they are revealed to the human ear.

        As I know for certain that those noises were not part of the performance or recording, I don't want to ever hear them. And as they would vary from pressing to pressing, replay system to replay system, listener to listener they are adding a degree of randomness which was neither in the composer's mind nor that of the conductor and orchestra.

        * In practice, the theoretically wider frequency response of vinyl opens-up wider audio spectrum to clicks (impulsive noise) which can indeed extend out beyond 20kHz and add nothing to the music whatsoever.
        Alan A. Shaw
        Designer, owner
        Harbeth Audio UK

        Comment


        • #5
          The digital divide?

          Hi Alan

          I am still having a hard time getting an image of treacle running down my Harbeths out of my head!

          If we agree with your points about digital reproduction as correct ( and I have no reason not to), then those who argue that there is something about vinyl that makes it "better/fuller/real, are simply imagining things?! I like listening to vinyl, but I think that it may be the contemplative act of putting on a record, and forcing myself to listen to the music; each track. It is not a convenient medium to say the least, and when CDs came out, I like many others cheered the convenience...and yet, we still hear the argument that digital is too clinical, dry, etc., and companies strive to add an analog sound to their equipment - SACDs, DACs, cables and cords etc., that cost silly amounts of money.

          We know that we can hear the difference between AM and FM radio signals as well as the sound emanating from cheap speakers driven by cheap equipment when compared to good/very good equipment, thus, I assume that this ability to hear the "difference" drives the digital/vinyl divide. These two opposing forces intrigue me, and thus the post.

          Or maybe we just need a bit more treacle...;-)

          Cheers

          George

          Comment


          • #6
            Vinyl, audio performance, AM-FM preferences

            Originally posted by Macjager View Post
            ...If we agree with your points about digital reproduction as correct (and I have no reason not to), then those who argue that there is something about vinyl that makes it "better/fuller/real, are simply imagining things?!...We know that we can hear the difference between AM and FM radio signals...
            Again, plenty to think about.

            First: I don't doubt for a second that the 'sonic experience' of vinyl is quite different to that of CD (I use that as a generic word for digital delivery). It is. It is subjectively and it is measurable. It's a fact. And vinyl may, on the right day with the right music on a sympathetically cut LP sound good, even great. But the acid test is really this ...

            1. Could we by some ingenious electronic processing make (or fake) a CD to sound indistinguishable from a vinyl of the same recording? Answer: Absolutely so, 100%. Quite easy to do on a digital-audio-workstation (DAW) or at home using, for example, Adobe Audition with some plug-ins.This process would require a 'down sampling' of the CD by throwing away all low level detail, adding crackles, surface noise, tracing distortion, harmonic distortion, intermodulation distortion, compressing the dynamic range, monoing the bass and narrowing the stereo width. All of this can be done.

            For a professional plug-in to achieve the vinyl-from-digital sound look here and read here. Picture here.

            2. Could we by some ingenious electronic processing make (or fake) a vinyl disk to sound indistinguishable from a CD of the same recording? Answer: Completely and utterly impossible to do this. Although we can digitally remove the clicks and some crackles, what we cannot recover is the microtones in the music buried under the surface hiss, assuming that the cutting head was of sufficient compliance that it could actually trace those extremely fine 'hairs' in the musical performance. But setting all that aside, the biggest difference between the vinyl and CD experience is one of measurable spectral balance. Or to put it simply, vinyl has more bass and less top. Not by design, not by intention - but as a by-product of the challenge of wiggling a relatively stiff and heavy diamond tip in a rotating groove cut in plastic. Nobody at the production side of cutting vinyl LPs wants that to be the case. They want vinyl to be the audio equal of CD. But that just isn't possible.

            Your second point about AM/FM reminds me of tests in the 1950 (or even before) where musicians actually preferred the AM sound over the new upcoming wider range FM sound. Are you aware of those? And just how could such a non-intuitive result be arrived at?
            Alan A. Shaw
            Designer, owner
            Harbeth Audio UK

            Comment


            • #7
              Vinyl vs. cd test

              Originally posted by A.S. View Post
              ...Could we by some ingenious electronic processing make (or fake) a CD to sound indistinguishable from a vinyl of the same recording?...
              I've already done some tests a few years ago, alone and with friends, where we compared the differences in sound from a cd and a vinyl. Both of them were playing simultaneously and we were able to switch on the fly from a source to another. Our two samples were: 1) Beastie Boys, Ill Communication and 2) Buena Vista Social Club.

              Nobody was able distinguish the cd and the vinyl.

              Since, few months, I was thinking about doing the same exercise with new LP that I have and with which the cd and MP3 are included. Those are interesting packages and more label are doing this now. 3 for 1! Here are my next prospects. Three excellent albums by the way:

              -Allen Toussaint "The Bright Mississipi"
              -Bill Frisell "Good dog, happy man"
              -Black Keys "Brothers"

              A small note on the "famous" suface noise. Many people refers to these. With a good stylus and a clean LP, there are none.

              Sebastien

              Comment


              • #8
                Musicians sonic preference

                Hi Alan

                Hmm, I had to give your comments a few read throughs, and then let them sit and percolate for the day! Addressing your question about the AM radio preference of musicians in the 1950s, I believe I came across some comments about this in one of the HUG threads. I would postulate that there are several reasons for the lack of enthusiasm on the part of musicians for "this new sound" that was to be unleashed on the public.

                First, as is often the case when there is a new concept or a new way of presenting a previously acceptable product, in this case music, the first reaction of most humans is to reject it; change is not something that comes easily to most people. A second reason could be related to how musicians aurally perceived this new radio sound. In some of the other threads, comment has been made about the way musicians hear music in the orchestra pit, or on stage - dry, little or no echo, loud, (especially in the days before stage monitors and earphones were available), that what they heard was probably very much like AM radio! FM radio sound tends to spread out the music - left to right, and is much less screechy, ie the highs are muted, and the music is smoother across the audible spectrum, not what you hear when you play music on an instrument alone or in an ensemble.

                My music teacher told me that when thinking about purchasing a new instrument - guitar or other - you should first let the salesman play it for you so you can hear what it sounds like; what others will hear, then you can see if you like the way it feels and sounds like in your hands.

                Now, as to the digital vs vinyl question, if there is a sonic signature, and microtones in a vinyl record, then I would argue that no end of adding things via a software program will truly make digital sound like vinyl. As to making vinyl near perfect in sound, getting it to sound sonically like digital is not possible, and I would argue, taking the wrong thing away from the music.

                The question may/should also be asked as to what are we trying to capture in our recording studios with musicians and thus what are we trying to reproduce and present to the listener?

                Cheers

                George

                Comment


                • #9
                  The hifi industry - chasing the wrong dream it seems

                  Originally posted by Sebastien View Post
                  With a good stylus and a clean LP, there are none.
                  With respect, your ears have fooled you. Surface etc. noises most certainly are there in tremendous quantities but as I said, they are masked under the music. Do you understand what I mean by 'masked'? I suggest you try the experiment with music of high dynamic range - such as the 1812 overture, which is simply a torture for an analogue system.

                  If your observations are correct - and I'm not arguing with you over this - then it means that the marketing basis behind CD/digital of >100dB dynamic range (compared to, at best, about 65dB for vinyl) is a pointless technical goal and that 24 bit recording offering >>100dB is completely unnecessary. If the consumer is truly satisfied with such a pitiful 65dB dynamic range with all the background grumbles and groans, >10% distortion etc. etc. then some serious questions have to be asked about the direction the hifi industry has taken these past 30 years!
                  Alan A. Shaw
                  Designer, owner
                  Harbeth Audio UK

                  Comment


                  • #10
                    Originally posted by Macjager View Post
                    ...Now, as to the digital vs vinyl question, if there is a sonic signature, and microtones in a vinyl record, then I would argue that no end of adding things via a software program will truly make digital sound like vinyl. As to making vinyl near perfect in sound, getting it to sound sonically like digital is not possible, and I would argue, taking the wrong thing away from the music.
                    I just want to clarify what looks like a misunderstanding of what I was attempting to say. I don't want to get too deeply into the vinly debate when many audiophiles quite understandably and righly enjoy vinyl (as I do, under appropriate circumstances). But there are no and cannot ever be 'microtones' in vinyl that are not present in digital recordings (CD to name one). It is utterly impossible. There cannot be 'microtones' when the dynamic range is so very narrow between the ever present background hiss/rumble/warp noise/tracking noises and the music. The constant roar of those noises is only undetectable to the ear because the music masks them. But they are there aplenty. If anyone has the opportunity to cut or to hear a test LP record where there is a long silent unmodulated grove with no music to mask the noises they are in for a shock! Nobody in the recording business wants to hear that noise rubbish overlaid onto their beautiful performance or recording.

                    I have never met anyone in the recording business who would ever, under any circumstances return to vinyl as a carrier. Like it or not, the fact is that a good digital recording made within the obvious capabilities of the digital medium (i.e. not clipped etc.) is exceptionally faithful to the original source.

                    The point is surely proven by this: take a master digital recording. Copy it once. Copy that one again. Copy that one again. And again, and make one hundred generations of copies of copies. Compare the 100th generation copy with the 1st generation sonically and in the lab using the best test equipment money can buy. They should be identical in every detail. Then take the digital master and cut it onto a vinyl pressing master. Make an LP from that. Compare that 2nd generation with the master - sadly no comparison. And to make further copies of copies would bring even the most dedicated vinyl fan to tears.

                    Finally to be crystal clear - the analogue (vinyl) process adds noises not present in the original recording and bends the overall sound spectrum. The result is that those added noises obscure or take away detail in the recording. They cannot add detail or anything to the performance or recording - only degrade it. Anyone serious about vinyl absolutely must have a proper vacuum-based record cleaning machine.

                    The sad part for me is that there are many staggeringly beautiful turntables, tone arms and cartridges available including the SMEs made near Harbeth UK. They are technically perfect. That's not the issue - the weakness is the vinyl medium, not the mechanical replay system.

                    Look here at repairing vinyl
                    .
                    Alan A. Shaw
                    Designer, owner
                    Harbeth Audio UK

                    Comment


                    • #11
                      With our ears speaking - the superiority of clean vinyl

                      Originally posted by A.S. View Post
                      With respect, your ears have fooled you. Surface etc. noises most certainly are there in tremendous quantities but as I said, they are masked under the music. Do you understand what I mean by 'masked'? I suggest you try the experiment with music of high dynamic range - such as the 1812 overture, which is simply a torture for an analogue system...
                      Yes, I absolutely understand the expression "masked". That's why, even if we don't have a music with an high dynamic range, we usually heard those noises between the different tracks of a LP. Simple as that.

                      I want to be clear again, with a good and clean stylus and vinyl, there are no noise a human ear can hear. If we talk about any other vinyls, not cleaned and used with a dirty or bad stylus, I totally agree with you, there are surface noises. For example in my vinyls collection, I have many of them bought new and well taken care of that sound incredible but there is a part of my collection which are used, old, unclean, that have a lot of surface noises.

                      While, I'm not familiar with the latest digital formats, I'll be curious to heard such dynamic range. Theory beside and only with our ears speaking, which medium sound the more natural? Many will tell you the vinyl. On my side, live music sits at the top.

                      Sebastien

                      Comment


                      • #12
                        Originally posted by A.S. View Post
                        It's rather obvious to anyone at the recording end of the process that for points1-9 (and in practice 1-10) that digital reproduction is technically superior by a very big margin. Despite that, many listeners - me occasionally included - can enjoy listening to vinyl. But if we're honest, for 'emotional reasons' concerned with the performance of playing vinyl not for an technically justifiable reasons.
                        Is it possible that one of these "emotional reasons" is the the distortions of vinyl may actually be perceived as benign and in fact pleasant by some listeners?

                        For example, an unamplified electric solid-body guitar on its own sounds rather flat and uninteresting, with not much body to the sound. But run it through an overdriven Marshall amplifier head, with those EL34s adding those beautifully fuzzy overtones, all that terrific harmonic distortion, and suddenly it sounds just great (if it's not overdone): thicker, fuller, warmer, richer - just not a whole lot like the original instrument. Maybe vinyl replay does something similar?

                        Comment


                        • #13
                          Yes i do agree that a well setup vinyl system sounds more natural & expressive than CD. However, due to the inherent musicality & correctness of Harbeths, i can enjoy lesser recordings on CDs as well.

                          Comment


                          • #14
                            Listener preference - a matter of exposure

                            As with so many - all? -audio issues, research has been undertaken sometime during the past 100 years which we can draw on. The human ear certainly hasn't evolved during that time (possibly even regressed due to continuous ambient noise of city life?) so we should not reject any solid research work just because it's printed on yellowing paper.

                            This whole subject of bandwidth v. listener preference has been studied before. For example, British audio engineer James Moir reported on this very issue in 1947/48 at the start of the FM radio era which opened-out the hifi window from the previous AM (medium wave) system. And the shocking, counter-intuitive result from a sample of 500 listeners under controlled Chinn-Eisenberg* conditions? There was a strong preference for the narrow-band warm sound of AM over FM. Especially amongst musicians. 83% of musicians preferred the AM sound over the FM on classical music.

                            I'm sure we've all experienced this ourselves and it's easy to simulate this experience. Set off on a long car journey tuned to an AM radio. Resist the temptation to switch to FM, CD, cassette. Either listen to the AM radio with all its limitations or sit in silence. After three or four hours AM listening switch to an FM radio station. Doesn't it sound thin? All top and no bass. But we know that the audio bandwidth is at least two or three times wider and there is almost no background interference. But it takes some time to become accustomed to FM. The switch back to AM is however much more palatable than FM to AM. Try it yourself.

                            Conclusion? What we consider 'normal tonality' in audio reproduction depends upon our prior exposure. I'm certain that when the vinyl record appeared those used to the 78 found it equally distressing at first and the appearance of the CD equally distressed some accustomed to the LP. What is relevant is that the young generation have wholeheartedly embraced digital and would, of course, never revert to vinyl.

                            *After a long search I found this for you. IMHO this comprehensively concludes the subject.
                            Alan A. Shaw
                            Designer, owner
                            Harbeth Audio UK

                            Comment


                            • #15
                              Music on my Harbeths ...

                              Originally posted by Gan CK View Post
                              ... However, due to the inherent musicality & correctness of Harbeths, i can enjoy lesser recordings on CDs as well.
                              Absolutely! There are some harsh sounding cd from the 1990's which are a delight to hear via my Harbeth. They soften the sound of these.

                              S.

                              Comment

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