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Testing audiophile claims and myths

Discussion in 'Sound Science' started by prog rock man, May 3, 2010.
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  1. KeithEmo
    It is funny how that circle keeps going around and around....
    (Although I'm not sure where it exactly started this time.)

    1)
    You pointed out how a null test will demonstrate even the tiniest differences...
    I agree entirely, however, as I pointed out, if you null two of anything carefully enough, you always fine a little difference...
    So, rather than prove "two things are actually identical"...
    We always end up back at "now that we know exactly what the difference is we have to decide whether it counts or not".
    At which point someone chimes back in with that mystical knowledge that a certain null is "good enough we can act as if it's inaudible without bothering to test it".
    (I suspect you're right, and that some difference is "small enough to be inaudible", but I'm not quite sure exactly where that number lies... maybe we need to test it.)
    (And I think that's even more true with digital systems - where you can have extremely large measured differences that only occur for very brief amounts of time.)

    2)
    I do apologize for #2.
    I personally am willing to accept that the results from those particular tests were what you say.
    (But a lot of other folks on this forum seem to think that "all claims are anecdotal if we don't get the data that goes with them".)
    And, yes, those results are interesting... especially that they show that, at least under those conditions, experience seems to be more significant that "raw hearing acuity".
    (But we still don't actually know if the massive difference in the hearing acuity of a five year old would override that difference - until we test it.)

    3)
    That's good... and eliminates one possible issue with the results that many others seem to overlook.
    (Like the tests that only include the rather narrow demographic of members of some particular "audiophile group".)

    4)
    Perhaps "common sense" was a poor choice of words.
    When we design a test that is intended to "prove a general case"....
    The general advice is to include any and all test samples that may reasonably be expected to prove the case.
    Since a single outlier renders you unable to make a generalization about "everyone" you have to try as hard as you can to find all the outliers.
    This is always a balance between practicality and thoroughness... and always ends up excluding a few that "everyone agrees won't matter"...
    This is a flaw that is present in all tests and is, for all practical purposes, unavoidable.

    I would, however, point out that it is much more of an issue in some situations that others.
    For example, there is a lot of incentive provided for fast human runners to come forward.
    The possibility of an Olympic gold medal, and a few $million in endorsements, makes it extremely likely that most fast runners HAVE been clocked.
    Even further, anyone who exhibited unusual aptitude in school has a good chance of receiving additional training to achieve their maximum potential.
    However, there is no such clear-cut incentive for people with exceptional hearing to come forward and be tested.
    Therefore, in practical terms, only a tiny percentage of every human on Earth has even had their hearing tested.
    (At a wild guess... very few five year olds, with their excellent hearing acuity, has ever gone to a course to train them how to listen properly.)

    5)
    On the last part of your last comment...
    I very much doubt we have many five year old customers...
    (And, to be honest, I doubt many of our customers would buy equipment just because their five year old child preferred the way it sounds.)
    However, as has been pointed out so often, this is not a forum about marketing... but about science.
    Whether, if five year olds could hear a difference, there would be any commercial value to that fact is a matter for another forum.
    I'm merely curious, for scientific purposes, whether it may happen to be true or not.

     
    Sonic Defender likes this.
  2. GearMe
    I'd expect this might vary somewhat by individual, the setting, etc. Gregorio would have better insight than I would.

    Not sure what 110-120 number you're referring to but I'm just using numbers that can be found on OSHA or in studies on the web.
    According to OSHA, they allow 2 hours at 100 dB TWA; 1/2 hour at 110 dB

    So...as an example, someone hitting the Club for the night at 110 dB TWA is risking hearing damage if they stay longer than a half-hour. On the other hand, someone experiencing momentary peaks at 110 dB is not at risk...if their TWA level is 90 dB or less over an 8 hour period or 95 dB over a 4 hour period.
     
  3. gregorio
    1. Yes, under some circumstances. The audience is not going to get that at a piano recital, they might possibly get it with one of the big, late romantic period or later symphonies. However, we're talking about probably one or two such peaks, maybe a handful, in a 45min symphony.
    1a. So firstly, it wouldn't be a "constant flinching", it would be very occasional/exceptional flinching. This isn't the case with some popular music genres though, where the peak level is likely to be hit quite a few times even in a short 3-4 minute song, due to the quite heavy compression employed. Why would people pay good money for this? For the same reason that people pay good money to flinch at a horror movie. It is in fact possible to induce a sense of euphoria from high SPLs, a fact often exploited in heavy metal genres in the past. However, it's become apparent over the last 3 decades or so that such SPLs come with a very significant risk of hearing damage.

    2. In fact, some of those calculations correspond to actual events. For example, the world record loudest ever gig was held for quite a few years by The Who. At 32m from the speakers at The Valley (football stadium) gig, the peak level was measured at 126dB. Obviously though, the very fact that it was the world record holder demonstrates that this was truly exceptional and not the norm! Additionally, in the '70's and '80's when being the loudest band was a serious point of pride and marketing for a number of high profile bands, they all suffered very significant hearing damage and in the late '80's Guinness dropped the category of loudest band, on the grounds that it did not want to encourage hearing damage.

    3. OSHA sets the occupational noise limits for industry and is regularly lobbied by large industries/corporations. The WHO on the other hand seem more concerned with limits damaging to health, rather than being acceptable to industry. I believe their current recommendation is peak levels no higher than 110dB, not 131dB.

    4. Yes it does, if their "use case" is dangerous! Depending on what sort of music bigshot is listening to, his reference level is not unreasonable, especially if we don't fail to ignore the fact that at the same SPL, music/audio will subjectively sound much louder in a small room (such as a sitting room) than in a large room (such as a cinema or concert venue).

    G
     
    Steve999 likes this.
  4. KeithEmo
    I agree.....

    I would also say that it should be up to the individual listener to decide what levels they personally prefer.
    BigShot may prefer to always listen at what he considers to be comfortable listening levels...
    Someone else may actually feel that you're supposed to flinch when those cannons go off in the 1812 Overture...
    And hearing a really loud noise that makes you jump once in a while isn't dangerous... and may add a lot to your sense of realism.
    (Remember the scene in Tommy, where the Acid Queen smashes the mirror.... it's supposed to make you jump.... because smashing a mirror is really loud.)
    And someone else may just occasionally "want to make their ears bleed" - even though they know it's probably not a great idea.
    (But, yes, if you want to claim that your system can reproduce a symphony orchestra accurately, then it should be able to recreate the original levels involved, including the cymbal crashes, and the cannons.)

    I should also point out that the idea that "a device only needs to be able to perform exactly as well as you need it to" is somewhat misleading.
    Many of us don't generally drive over the 55 mPH speed limit...
    Yet very few people I know would be willing to purchase a car with a governor that absolutely limited its speed to 55 mPH... or a car that just plain couldn't go any faster...
    In fact, everyone I know owns a car that can go far faster than they could safely drive it.
    (After all, you may occasionally need to go a bit faster, to pass someone, or just because you're in a big hurry...)
    It makes equal sense to expect your audio system to be able to play louder that your typical listening level - for those days when you just want to turn it up a bit.

    It's also worth noting that our perception of loudness varies considerably.
    An average level of 80 dB is going to sound far louder to someone arriving home from their job as a librarian...
    Than it is so someone arriving home from their job repairing jet engines...
    So, odds are, their typical listening levels are likely to also vary considerably...

     
  5. bigshot
    Actually experiencing sound is the best way to judge it. When we say things like "loud normal listening level" it can be very difficult to assign a specific number to it. How loud is loud? How normal is normal? Where are you sitting? What kind of music? What kind of room? But if you are in your living room and turn the music up to the loudest comfortable volume and measure it, you can find a specific number that applies to your situation. It might be a little different than mine because my situation might be a little different. But it will be in the same general ballpark. At least by hearing it, you have some experience to know what that number sounds like.

    The way I figured out my rules of thumb was to sit down with a sound editing program hooked up to my stereo and to experiment with various parameters of sound to hear the effect. You don't have to be clinically precise or use fabulously expensive testing equipment, you just have to get a feel for what a frequency or volume level or flavor of dynamic compression or whatever you're trying to figure out actually sounds like.

    Too often audiophiles look to abstract numbers on a chart to justify pushing limits beyond what is necessary. For instance, there was one guy who claimed human ears demanded a noise floor of at least -120dB. The only way you arrive at such an extreme position like that is to not know what a peak level of 120dB sounds like... to have never figured out what a listening room's natural room tone is... and to have no concept of what kind of dynamics commercially recorded music is designed to have.

    Other people claim that there are instances of people who register brain waves to super audible frequencies. But what do those frequencies sound like? (or more specifically NOT sound like?) And what happens if you take your favorite SACD and do a high pass filter at a specific point. Theory and measurements are great, but how important is 5kHz or 15khz or 25kHz or 35kHz to Beethoven's 9th symphony? You only know the answer to that by listening.

    Everyone around here likes to put on white lab coats and serious expressions and talk about precise numbers and exacting standards, but that isn't how human ears work. There's a range to perception. Specific points within that range mean a lot less than a feeling for the overall range itself. Understanding the context of the abstract numbers comes by listening and experimenting, You really shouldn't look down your nose at a suggestion to grab a $60 SPL meter and figuring out what 80dB peak sounds like with your own music on your own stereo. Doing that might teach you something more useful than all the charts in all the books on your shelf.

    By the way, I've attended Wagner's Ring Cycle, which is probably one of the loudest things you can experience in the concert hall. It didn't get up anywhere near 90dB in my seat in the middle of the house. It was more in the range of 60-70dB with maybe a horn blast once in a while that went a bit above that. I listen to music on my home stereo louder than I've ever heard music in the concert hall and I don't get much above 80dB there. But I admit, most music I listen to doesn't have atomic bombs going off. Most of it is within a dynamic range of 45 to 50dB. I think Gregorio might be basing his loudness estimate on standard miking positions for recording in an empty house, or perhaps short impulses of less than a second. That isn't the same as a loud listening level for commercially recorded music.

    As for OSHA standards, 90dB is the top limit for long term exposure. 120dB is forbidden even for very short exposure times. 120dB is the threshold of pain. I can't picture what 130dB would be like and I don't want to find out. When you get sustained sound levels above 90, you are in the danger zone and it sure isn't comfortable to listen to music that loud. Again, grab a SPL meter and get a feel for what these numbers represent. It's all too easy to interpret the numbers to justify incrementally more and more until you get into the range of crazy town.
     
    Last edited: Jun 14, 2019
  6. TheSonicTruth
    Half an hour at 110dB SPL?

    I can't evrn tolerate 95dB in my church for 30 minutes!

    "TWA" - Wasn't that an airline??
     
    Last edited: Jun 14, 2019
  7. castleofargh Contributor
    from the few tests I've done, I don't seem to ever let my music peak at 90dB at home, be it with speakers or headphones. most of my casual listening time at night will probably peak 20dB below that. a few very dynamic tracks probably peak higher, but if they're really stupidly dynamic tracks, chances are they're not in my playlists because I can't hear **** on the quiet parts, or I really like the track anyway so I've compressed it to hear something.
    as for a live event, if it's loud I'll have prepared earplugs, won't go, or I'll leave after a few minutes. it's been socially awkward a few times, but why would I endure something that bothers me and might be bad for my ears?
    I went to see a specialist long ago because I had read about some hypersensitivity troubles and thought I had that. the guy diagnosed me with an acute case of not enjoying loud sounds and being a dick about it. which apparently is not actually classified as a disease and doesn't have a treatment.
     
    bigshot likes this.
  8. KeithEmo
    The treatment is good earplugs.

     
  9. GearMe
    Thanks for the reply...

    Was being a bit snarky/sarcastic re: Bigshot's 'flinching' comment...sorry if that got lost in translation!

    I get your view on #4 but tend to be a 'audio libertarian' on this...the way someone wants to listen is their business as long as it's not disturbing someone else.

    Don't agree with motorcycle helmets either (though I've never ridden a bike...even as a passenger)

    You wanna listen at low levels? Fine...put on some Kenny G and well, um...(go to sleep?)
    [​IMG]


    You wanna put on Quadrophenia and blast the JBL's? Even better!
    upload_2019-6-14_15-34-47.jpeg
    (FWIW, I'm reasonably certain that it's a Federal offense to play The Who at less than 90 dB!) :ksc75smile:



    After all, to quote Jimmy Buffet..."It's 5:15 somewhere"
    (now...here's some mellow, mood music to ease into the weekend) :wink:








    Gads...just listening to Quadrophenia makes me want to buy a set Klipschorns :astonished:
     
    bfreedma and Glmoneydawg like this.
  10. TheSonicTruth
    I've always disagreed with the notion of needing ear muffs or plugs in live music scenarios(concerts, worship, etc.). They are like closing port holes on Titanic.

    Consider, instead, more smaller arrays or individual speakers, placed at regular intervals around or in the spectator accommodations.
     
  11. analogsurviver
    In an ideal world, where musicians would not be loading 5 k worth equipment into 500$ car for a 50$/head gig - or worse, being forced to play for free to get "exposure" - where there would be enough time for sound check ( it has to be said musicians themselves are many times too late on the premise to make a decent sound check ... ), where venue owners would not give preference to new mirrors and other decor while skimping on "acoustics" to the max , etc & so forth - maybe.

    Not many bands can or wish to afford their own permanent sound engineer - who in no time becomes, de facto, n+1 th member of the band. It is hard enough as it is - even for the permanent sound engineer, following the band from venue to venue, even if the band has its own sound equipment. If it is necessary to use whatever is at any given venue, the task gets even tougher.

    Adding more smaller speaker arrays would compound the problem further. Setting up, calibrating, adjusting proper delay, etc would take too much time for most scenarios.

    Anyone who has done anything of the sort will also tell you dismantling everything takes almost the same time as setting up - and while the musicians could/should sleep, roadies MUST truck gear to the next venue, to be set up for another concert next evening.

    Not many bands can afford arrays with delay - like Rolling Stones on that beach - for XY.000 spectators, who were paying a sustainable entrance fee.

    Even less clubs are willing to have a permanent arrays of multiple speakers - as it would llimit the number of table$ for le$$ strictly musical events.
     
  12. KeithEmo
    That's a nice idea... but in practice it's very difficult to achieve. The problem is that sound travels slowly through air (about one millisecond per foot). Because of this, there's no way to use a bunch of small arrays, widely scattered, to create a consistent sound field throughout a large area. if you place two speakers fifty feet apart, and play the same audio through both of them, someone standing directly between them hears a single sound, but anyone standing too close to one or the other will hear sound coming from the other delayed, which will sound like an echo. In order to avoid this, you have to make sure that anyone standing too far off center cannot hear sound from the far speaker. You need to ensure that the sound from the near speaker dominates what they hear well enough that they won't notice the sound from the far speaker.

    If you were to place one speaker every 20 feet around the edges of a large room, each person would hear the sound coming from the nearest speaker with no delay, and the sound coming from the two speakers twenty feet to either side, at a slightly lower level, delayed by 20 milliseconds, and so on. The result is that, if you can hear sound from speakers more than about fifty feet away, it sounds like a clear echo. And, even worse, sound from speakers that are closer won't sound like an echo, but it will turn what you're listening to into a blurry jumble of sound that is totally unintelligible. There are ways to avoid this, but they involve very carefully positioning directional arrays of speakers so that the sound anyone hears in any particular spot is dominated by a single set of speakers. If you look at very large stadiums, they often have speakers up front facing the audience, then arrays positioned further out, on poles, also facing out. They may also have arrays positioned far above the audience, positioned to fire over the heads of the front rows, and so only be audible further out. However, the speakers that the outer rows hear must be positioned or directed far enough out that the people who hear them don't hear the sound coming from the front speakers. If you don't get it right, the entire venue sounds like a giant cave, with massive echoes, and very poor intelligibility.

    Large sports arenas and other dual-purpose venues have an even worse situation. One thing that helps minimize the problem I described is to use room treatments on the walls and ceiling, to at least minimize the reflected sound reaching each listener from distant speakers. However, room treatments costs money, and they reduce the overall sound level in the room... meaning that you need more power to achieve reasonable listening levels (or the loud levels many bands and their audiences want). You will often see room treatments used in real symphony halls and similar venues - but rarely in venues like sports stadiums that are occasionally also used for rock concerts.

    All told, it's very difficult to achieve a pleasant listening level over a large area.
    It requires a significant amount of planning, some compromises, and a willingness to spend more money to optimize the sound of the venue.

    In short, it's something that you would expect a high quality symphony hall to do....
    But you're not likely to find it in the sort of bar where each band "brings their own PA system and sets up between music sets".

    Of the fifty or so concerts I've heard....
    Four or five were performed in venues that sounded really good....
    Maybe a dozen were performed in venues that were at least credible....
    And the other two thirds were in venues that were very loud but had the acoustics of a gymnasium....
    (And, like it or not, a popular band will sell out in either.... )

     
    Last edited: Jun 14, 2019
  13. Steve999
    A dB meter is nice to have. If anyone is interested, you can download a dB meter app for an iPhone, but I find it under-estimates decibel levels for content that is bass heavy. My stand alone decibel meter seems more accurate. (Remember I have two subwoofers ; ) ). I’ve also compared the iPhone app to the real dB meter for lower notes on the piano and the levels shown on the real dB meter are higher, I think the iPhone mic just is not sensitive enough to lower frequencies. I don’t think android devices are standardized enough in terms of the mic to make a dB meter app reliable or practical, but maybe they are.

    So right now I am in my listening area with my nicest stuff (which many would consider quite mid-fi I’m sure). The noise floor for the room measures about 32 dB. I am watching a baseball game with fast a-weighted peaks at about 54 dB, and I still find the sound very pleasing at that volume. I am sure my receiver is doing all sorts of mumbo jumbo to make such a low volume still sound satisfying. My receiver says “PCM [dolby digital symbol] Surr.” whatever all that means. I’ve got the surround sound on with two towers, two surround speakers, a center channel speaker, and of course two subwooofers. Anyway, it sounds really nice, and the dB meter is my companion for a lot of things, like making sure the output from the subwoofers is proportionate with the rest of the system, checking how well the auto-room-calibration feature from my receiver is working in terms of distance and relative loudness of the speakers (the receiver can put out a test noise signal for each speaker so I can double-check), checking noise floor for my room, getting a hang of where the sweet spot in terms of volume is for me for music enjoyment, so I don’t have to use trial and error, etc. Also, if I understand correctly, the receiver auto calibration and auto eq uses a 70 dB signal to calibrate the volume at which a flat response will be best approximated from my seating position. So maybe that tells you something, that 70 dB seems to be the reference level for a flat response. As the volume gets turned down perhaps it does whatever (adds some bass and a little less treble I guess) to keep things sounding satisfying.

    So the point is. . . wait. . . I forgot, Oh well. If you read this thanks. I tested some things. With a decibel meter.
     
    Last edited: Jun 15, 2019
  14. dprimary

    The one from Studio Six Digital was able to bypass the built-in filters in the microphone to get a more flat response. Of course you can get a low cost calibrated Type 2 microphone from them for $200 that is really handy. They also have measurement preamps and Type 1 microphones if you need that.
     
    Steve999 likes this.
  15. dprimary
    d&B Soundscape pretty much automates all that, connected to a performer tracker it positions all the performers in the soundfield even while they move across the stage. If the performer in the middle and you are in the left of the hall there sound to you will be to your right where the performer in on the stage, if you are on the right side of the hall there sound will be to your left. They can walk around the whole audience and the system will track them though the many dozens of loudspeakers in the room.

    Every Cirque du Soleil sounds really good and they use hundreds of loudspeakers they even manage to make the Beatles palatable, of course replacing all the drum tracks was a vast improvement.
     
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