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Difference in level (loudness) - situations in which this occurs

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  • Difference in level (loudness) - situations in which this occurs

    We here on HUG have repeatedly mentioned the significance of the loudness variation when comparing audio events, including musical instruments, sound recordings, loudspeakers, audio amplifiers and so on. The science of audiology is based on understanding this predictable character of the human ear and has been studied in great depth for nearly one hundred years. The ear/brain interaction is one of the best understood in medical science, as a little desk research will prove to you.

    Despite this, there is little or no effort made in audiophiledom to treat this core nature of the ear brain with due respect. The importance of taking care to make sure that event A and B are loudness matched, fundamental to a valid, repeatable comparison, is rarely discussed, less so implemented in making audio comparisons.

    I wonder if this is in part due to a disconnect between the discussion of 'loudness', as a scientific measure, and spotting instances where loudness variation can creep into the comparison of A and B. Can we start a list of examples where a loudness mismatch is present?

    1. Moving one row closer to the orchestra
    2. Moving one row further away from the orchestra
    3. Swapping to another speaker stand that is 2cms shorter or taller
    4. Comparing a vinyl record with the same performance on CD
    5. Turning the volume control the smallest step
    6. Closing the curtains in the listening room
    7. A second person entering the listening room
    8. Swapping to another source
    9. Selecting a different radio station
    10. Selecting another streaming source
    11. Changing LP records
    12. Changing CDs
    13. Playing another DVD
    15. Pulling up your shirt or jumper or jacket collar
    16. Room temperature 15 degrees or 30 degrees
    17. Hearing acuity at age 50 compared with 35
    18. Pulling loudspeakers forward 10cms
    19. Pushing speakers backwards 10cms
    20. Rearranging furniture in the listening room

    Your thoughts?
    Alan A. Shaw
    Designer, owner
    Harbeth Audio UK

  • #2
    Suggestions

    My thought is that there is another factor:

    21. Perception of loudness varies over time in a way that is related to what you are listening to. For example, the typical listening session starts off quiet, but the volume is cranked as the evening wears on. It doesn't sound any louder at the end!

    To that we could add:

    22. It may be impossible to 'level match' two setups if they are tonally different - and in the speaker world this may be a fundamental part of the experiment.

    Comment


    • #3
      More

      Hmmm - I would not have given too much thought to some of the things in that list before this challenge, but now that you have listed those 20 items, the only one that I think would not change the loudness is number 17, assuming that any A/B comparison does not take place at age 35 and then a long wait until reaching age 50 :-)

      {Moderator's comment: They all have a bearing on 'loudness' regardless of time period.}

      Comment


      • #4
        Additional loudness factors

        Originally posted by A.S. View Post
        I wonder if this is in part due to a disconnect between the discussion of 'loudness', as a scientific measure, and spotting instances where loudness variation can creep into the comparison of A and B. Can we start a list of examples where a loudness mismatch is present?
        Your thoughts?
        23: changes in blood pressure (physical)
        24: changes in air pressure (physical)
        25: humidity (physical)
        26: electro static changes when a mobile phone rings (physical)
        27: pre-biased in favor of A or B (psychological)
        28: being distracted - not fully concentrated (psychological)
        29: illness (physical/psychological)
        30: being medicated (physical/psychological)
        31: asking one self "what the hell am I trying to prove here?" (psychological)

        The disconnect will always be there because this list will be endless just as human brains function endlessly different from person to person, from moment to moment.

        Winfried

        Comment


        • #5
          Local background noise

          One of my pet peeves. I nevertheless rarely convince people just how incredibly important this step of matching loudness is when comparing items.

          32. A change in the listening area noise floor.

          You know the HVAC kicks on. Often unnoticed, but never without changing the noise floor. It has the effect of a sound level change. Or the obverse if it kicks off while doing a comparison.

          Another related one. You often see people talk about cleaner electricity at night and much nicer the system sounds. Almost surely they simply are experiencing the results of late night being quieter. The cliche example is listening to the ol' rig quite comfortably late at night. Turn on the same rig the following day, and finding the volume needs advancing considerably to come close to listening comfortably.

          Comment


          • #6
            Don't want to hear, or see....

            Originally posted by esldude View Post
            One of my pet peeves. I nevertheless rarely convince people just how incredibly important this step of matching loudness is when comparing items.

            29. A change in the listening area noise floor.

            You know the HVAC kicks on. Often unnoticed, but never without changing the noise floor. It has the effect of a sound level change. Or the obverse if it kicks off while doing a comparison.

            Another related one. You often see people talk about cleaner electricity at night and much nicer the system sounds. Almost surely they simply are experiencing the results of late night being quieter. The cliche example is listening to the ol' rig quite comfortably late at night. Turn on the same rig the following day, and finding the volume needs advancing considerably to come close to listening comfortably.
            You won't convince people that loudness (i.e. level) is by far the most significant factor that they do not bother to control when making audio "comparisons" - which are not actually comparisons at all. They are self-delusions, not intentionally obviously, but as a consequence of the lack of experimental controls.

            If the pharmaceutical industry had the casual approach that those who "compare" hifi equipment have to the evaluation of the efficacy and risks of drugs they develop, one's chance of survival after taking them would be a lottery with death.

            Almost everyone would be aware that the quality of a photographic image taken with a camera is closely correlated with how wide the lens aperture is open or closed. In effect, the film or image sensor receive light rays the quantity of (or in sound terms the loudness of) which has absolutely predictable consequences for the captured image. It doesn't matter what make of camera, or lens, or whether the image is on film, plate or a digital sensor: the relationship between the quantity of light and the image our eyes subsequently perceive is 100% absolute and predictable.

            And so it is with sound. Name a brand and a sound recording or reproducing device, and there is a rock-solid correlation between how loud it plays (its sound level) and the sound image created in the listener's brain. It can't be helped.

            Pointless even attempting to think of disproving that any more than challenging the rules of optics. It is the Rule of Sound Evaluation. Our eyes are brightness sensitive organs. Our ears are loudness sensitive. Our skin is temperature sensitive. That's how we are!

            If you don't control the loudness, precisely, of A v. B under evaluation, you might as well save yourself the bother of doing any sort of "comparison" and just pick the one you like the look of, or the features of or the build quality of.

            33. Time pressure: having to reach a conclusion in a hurry (psychological)
            34. Reading a review section of a hifi magazine as you listen (psychological)
            35. HiFi salesman silently observing you as you listen, in your line of sight (psychological)
            36. Eyes open and looking at hifi equipment (physical/psychological) - a big mistake
            37. Passing traffic, seen or heard, incl. sirens (physical/psychological)
            38. Relocating your listening position during session (physical/psychological)
            39. Door to listening room opening or closing during session (physical, maybe psychological)
            40. Tea/comfort, food breaks (physical)
            41. Fag breaks (physical/psychological)
            42. Awareness of others moving around out of sight behind listener (psychological)
            43. Change in natural light level during session - afternoon to evening, or artificial room lighting (psychological)
            44. Messages or calls arriving on listener's mobile phone (psychological)
            45. Ringing of demo facility phone or door bell (physical)
            46. Conversations in the demo room or in adjacent room or corridor (psychological)
            47. Bleed-through of noise from adjacent rooms (physical)
            48. Gaps in comparison between A and B
            Alan A. Shaw
            Designer, owner
            Harbeth Audio UK

            Comment


            • #7
              I still question whether level matching per se is possible unless the two systems being compared are, to all intents and purposes, identical. If they have

              - different frequency responses
              - differing dynamic compression characteristics
              - different distortion characteristics (that may vary dynamically with signal level)

              then the signal content used for the matching, and levels at which you say they are "matched" are to some extent arbitrary.

              Comment


              • #8
                Mismatching

                Originally posted by G Spiggott View Post
                I still question whether level matching per se is possible unless the two systems being compared are, to all intents and purposes, identical. If they have

                - different frequency responses
                - differing dynamic compression characteristics
                - different distortion characteristics (that may vary dynamically with signal level)

                then the signal content used for the matching, and levels at which you say they are "matched" are to some extent arbitrary.
                We invite you to work through the issues here for public review and comment.
                Alan A. Shaw
                Designer, owner
                Harbeth Audio UK

                Comment


                • #9
                  49. Strategy of arranging two pairs of loudspeakers for comparison. Both simultaneously present in the room? Positioned how? Left A, left B, right A, right B? Left A, left B. right B, right A?
                  Alan A. Shaw
                  Designer, owner
                  Harbeth Audio UK

                  Comment


                  • #10
                    More factors

                    50. Moving closer to the speakers
                    51. Moving further away from the speakers
                    52. Speakers toed in more, less or firing straight ahead into the room
                    53. Turning the tone controls one step up or down

                    I'm not sure if items 23-48 are actually loudness factors same way as numbers 1-22 and 49-53. They rather change the attitude of the listener to the sound, but seemingly for different reasons than loudness change.

                    {Moderator's comment: Agreed that there has been some drift in the thread. Please keep submitting ideas and we will categorise them later.}

                    Comment


                    • #11
                      Meaningfully level matched?

                      Originally posted by A.S. View Post
                      We invite you to work through the issues here for public review and comment.
                      All 48 of them?! I don't think I need to: I don't dispute most of the enumerated items listed heretofore. Nor do I dispute the basic idea that in order to perform a meaningful comparison by listening, the two systems must be level matched. So for sure, in a comparison between ordinary PCM and the new wonder-process MQA, it is essential to start with the systems level-matched. In this case, I don't think there is a problem.

                      The issue for me, is that for more complex, audiophiliac systems, it may not be possible to match the levels except by specifying some arbitrary condition such as "All systems were level matched to within +/- 0.1dB at a standard SPL of 80dB using a 1kHz sine wave measured with an omnidirectional microphone at the same height as the tweeter at a distance of 1m". Yes, they are truly level matched at this point, but change the sine wave to 2kHz, or the level to 90dB, and suddenly they are not matched - unless the systems are substantially identical. Thus, a listening test to establish the difference between valve and solid state amplifiers, or vinyl and digital, or the desirability of a "house curve", has a problem: the systems cannot meaningfully be level-matched with real music. Merely stating an arbitrary condition (such as the one above) does not change this.

                      I think that this highlights an inconsistency in audio science based on listening: it concedes that touchy-feely audiophiles 'might have a point' by indulging their claims with a listening test, while simultaneously implying that audio is completely understood. If audio really is completely understood then we don't need the listening test, just the measurements.

                      Comment


                      • #12
                        Factors.

                        54. Room empty or crowded.
                        55. Folks seated or some standing.

                        ATB

                        Comment


                        • #13
                          Use more than one spot frequency?

                          Originally posted by G Spiggott View Post
                          All 48 of them?! I don't think I need to: I don't dispute most of the enumerated items listed heretofore. Nor do I dispute the basic idea that in order to perform a meaningful comparison by listening, the two systems must be level matched. So for sure, in a comparison between ordinary PCM and the new wonder-process MQA, it is essential to start with the systems level-matched. In this case, I don't think there is a problem.

                          The issue for me, is that for more complex, audiophiliac systems, it may not be possible to match the levels except by specifying some arbitrary condition such as "All systems were level matched to within +/- 0.1dB at a standard SPL of 80dB using a 1kHz sine wave measured with an omnidirectional microphone at the same height as the tweeter at a distance of 1m". Yes, they are truly level matched at this point, but change the sine wave to 2kHz, or the level to 90dB, and suddenly they are not matched - unless the systems are substantially identical. Thus, a listening test to establish the difference between valve and solid state amplifiers, or vinyl and digital, or the desirability of a "house curve", has a problem: the systems cannot meaningfully be level-matched with real music. Merely stating an arbitrary condition (such as the one above) does not change this.

                          I think that this highlights an inconsistency in audio science based on listening: it concedes that touchy-feely audiophiles 'might have a point' by indulging their claims with a listening test, while simultaneously implying that audio is completely understood. If audio really is completely understood then we don't need the listening test, just the measurements.
                          Would taking SPL measurements at various spot frequencies help, and then taking a sort of average position? But even so I would be happier if speakers were substituted into the exact same location, rather than compared side by side.

                          Comment


                          • #14
                            Serious comparisons

                            Harman Kardon designed a special listening room to evaluate speakers. Speakers are on some caroussel, moved into and out of the same ideal position, and all behind an acoustically transparent curtain to avoid expectation bias.

                            I bet they equalized levels.

                            Comment


                            • #15
                              Level matching and roll-off

                              Originally posted by willem View Post
                              Harma Kardon designed a special listening room to evaluate speakers. Speakers are on some caroussel, moved into and out of the same ideal position, and all behind an acoustically transparent curtain to avoid expectation bias.

                              I bet they equalized levels.
                              I'll bet they had a procedure that they defined as matching the levels, yes. Whether their definition was valid is a different thing. Noise will be better than spot frequencies if reflections are influencing the result. But if we are comparing a speaker that is flat down to 20 Hz with one that begins to roll off at 100 Hz, under what conditions can we say they are level-matched?

                              Comment

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