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In Reply to: Frequencies below 15kHz. mask the audibility of frequencies above 15kHz. assuming they are audible at all posted by Richard BassNut Greene on April 23, 2007 at 07:57:50:
"There are many complaints about FM radio sound quality.
But complaints about output above 15kHz. seem rare."What's to complain about? There basically isn't any :-)
Sorry, but you started out with this throwaway line and then threw it away anyway with your next sentence, so I couldn't resist this response.
"When listening to typical Western music on FM radio, it seems that the
tiny amount of sound energy above 15Hz., assuming there is any,
can be eliminated and few people, if any, complain about its absense."You're right, but is that because our expectations of the quality of sound from FM radio are less than our expectations for quality from other sources? I enjoy listening to FM and I think it does a good job of doing what it does, but I wouldn't compare its sound quality to CD or vinyl. I listen to the radio for different reasons to those that I listen to my audio system for, and I both expect different things and accept a lower sound quality. I suspect most people concerned with sound quality are similar, even those who want to extract the most from FM as a source and who buy expensive tuners and antennae in order to get the most from it. I don't think your point here proves anything that helps your argument.
"It seems to me that the people in the test said they preferred the music with content above 20kHz. WITHOUT ever proving they could hear a difference the two samples. ""A blind preference selection without the needed audibility test, is a typical high-end audio "blind test" (but not really a test at all)."It seems to me, from reading the table of the subjective results, that overall they thought that there was a difference on 5 parameters but that there was also not a significant difference in their like/dislike responses. The comment about preferring the sound with HF content is made in the text of the report but it did not seem to me to be borne out by the table of subjective results. That aspect of the report disturbed me. I think the authors assumed that if the subjects thought that the sound with hf content was perceived as "better" on those 5 parameters for which there was a significant difference, then the subjects preferred the sound with hf content. I don't think there was a strong preference for it because, if there was, then there would have been a statistically significant difference on the like/dislike parameter and there was not.
"A blind preference selection without the needed audibility test, is a typical high-end audio "blind test" (but not really a test at all)."
For a start we have the brain scans to show that there was a different response to the sounds with and without the high frequency content. There is also a statistically significant difference in subjective reports on 5 parameters. Audibility tests rely on the subject stating whether or not they hear the sound and that is a subjective report also. Determination of whether or not a sound is audible is done by whether or not there is a statistically significant response from a group of subjects, just as the determination of whether or not there were differences in the sound was made here. I think this is a valid test, but just because the test design is valid does not mean the results are valid. I think replication would be very good, especially replication with a variety of different sound types, before we started hanging too much on the results.
I'd also say that a "blind preference test", to use your terms (and I don't think the parameters on which there were significant differences in perceptions of the sound were preferences—I think the one parameter that did relate to preference failed to show a significant difference in perception) is valid. If people display a consistent and statistically significant preference for sound with hf content over sound without it, or vice versa, in a blind test, then it's plausible to believe that there is some attribute to the preferred sound that is linked to the preference. Whether or not that attribute is audible in isolation, ie the hf content on its own, is irrelevant. People may not be able to hear the hf content on its own but it may modify the way in which sound below the hf frequencies are perceived.
"There is also a possible question about how the energy above 20kHz was stripped from the music, and whether doing so created an audible artifact."Agreed—that is an issue to be concerned about.
There are issues with this study which deserve further attention, and I'd love to see it replicated a few times with a wider variety of subjects and sound types before I hung too much on the results, but it is a much better quality study than you seem to believe.David Aiken
Follow Ups:
The many test biases to "encourage" high frequency audibility:
-All the subjects were under 35 years old.
-Many were women.
-The Indonesian music had an unusual amount of high frequencies.
-Brain measurements were considered a proxy for "hearing"
-No one had to prove he/she could really hear a difference before stating a preference for music with and without the ultra high frequencies. (Beyond that complaint, the subjective evaluation conclusion didn't seem to follow from the data -- you covered that well in your post)I just don't see how this study could support a decision to buy a super tweeter.
I mentioned FM radio in my prior post because there are no frequencies over 15kHz. ... meaning that a small amount of sound energy is eliminated for broadcasta (this didn't read as clearly as it should have) ... yet that fact NEVER seems to be mentioned among the many complaints about FM radio sound quality (even complaints by golden ears who think every wire sounds different).
The best sound quality I have ever heard from a stereo was from a Redbook CD with no output over 20kHz. But then I can't hear 15kHz. anymore!
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Richard BassNut Greene
Subjective Audiophile 2007
That's a serious question.IF (note: big "if") you want to find out whether HF content can be perceived by listeners in some way (note: I did not say 'heard' for reasons I will state a little later), then I think as an initial test it is more than reasonable to start with subjects who are under 35 and largely female, and with music with a high HF content, because if you can't get a positive result under those circumstances you would seriously need to consider giving up on the hypothesis. If you get a positive result under those circumstances, then you could be encouraged to continue with a wider range of test subjects including strong representation from older people and males, and with music with less HF content to see just how perceivable the HF content is for a wider and more representative set of subjects and with a wider range of music if, of course, you were interested in the question from a musical enjoyment angle rather than a straight perception angle which I'm not certain the researchers are. I think it's actually worth while starting out by seeing whether people who are most sensitive to higher frequencies in sound show a response than by starting out with a sample of people who are less sensitive to higher frequencies or even with a group of people representative of the population as a whole. I'd rather establish that some "more sensitive" people show a response and then see just how representative their response is than come up with a negative result from a less sensitive group that leads to the question being dropped and ending up not knowing that some people do show responses.
Now, as to "hearing". Our various senses register a wide range of stimuli including, in total, a much wider band of the radiation spectrum than any single sense registers. We can feel low frequency sound if the volume is high enough, and we can feel subsonic frequencies that we can't 'hear'. Does that feeling aspect of low frequency perception affect our experience of the low frequency sound that we hear, and does it affect our enjoyment of that sound? Under some conditions, I think it does. I like the vibratory effect I've perceived with bowed double bass sounds at time, and it adds to my enjoyment of the auditory aspect of the sound. Testing has failed to show that people can hear pure tones much above 20 kHz, and that we lose the ability to hear the last 5 kHz or so of that with increasing age. Does that mean that frequencies above 20 kHz don't contribute to our perception of sound? Not necessarily. What if frequencies above that are perceived by one of our other senses, as subsonic frequencies can be perceived? If that is the case, does such perception modify our overall perception of sound containing HF content in its overtone structure? That's a hard set of questions to answer but they are worth asking.
What this study attempts to do is to ascertain whether there is a difference in perceptual response to sounds containing HF content to similar sounds with the HF content filtered out. The brain measures are a good, objective means of determining whether there is a difference in response and this study indicates that there were differences. That's a good starting point but there are a lot of things that need to be sorted out before one can know what that really means. Amongst those things that need to be sorted out are:
- whether this study can be replicated with different subjects from the same demographic (ie under 35, largely female) with similar test signals. The reason for that is simply that this is the starting point and if there was some problem with this study that threw up a false positive result, it would be nice to find that out early;
- next, if replication is possible, what happens when the demographics of the test group are changed to a more representative sample? How do age and gender affect the results?
- next, vary the test signals with different sounds and music to determine how the proportion and nature of the HF content affects the results.
- and somewhere in the process, start trying to find out just what mechanisms are involved in the perception of the HF content. Is it hearing or some other sense.
- finally, at least as far as science is probably concerned but hopefully a little earlier for those of us with more personal interests in this particular question, is resolving the issue of whether such perception—once we're genuinely satisfied that it is present—modifies our enjoyment of music and in which ways does it do so.
I reckon this is a damn good study for an initial foray into an extremely interesting area. It doesn't answer all of the questions, and it raises a few of its own, but at least it gives some good strong support to a push for further investigation into the area and I think that's a very good thing. I think it was worth doing the study and I think it was worth publishing the results as they are because that may well encourage others to look at the topic and that's essential to the process of finding out a bit more about it.
As for your final comments on FM quality and sound quality in general. I don't know whether the best sound quality I've heard is from CD or from vinyl because I've heard damn good sound from both and we know vinyl does contain higher frequencies than CDs do. I quite enjoy FM radio from time to time. I'm also 60 this year and, though I haven't had my hearing tested in years, I do know that I can't hear a 15 kHz test tone on my system at the levels at which I normally listen to music. I also know that I prefer the sound of CDs on my system (no vinyl source in my system) to the sound of FM radio. Is that because CDs contain higher frequency content than FM—content at frequencies that I know I can't "hear", because my CD player is of better quality than my FM receiver, for some other reason, or for a combination of 2 or more of those reasons? I don't know the answer to those questions and I'd venture to suggest that neither do you. At least this study is a first step to answering some of those questions and it's nice to see that step taken.
I'm not unaware of problems with this study but I'd rather appreciate it for what it does than rubbish it because I don't like its shortcomings and/or have severe doubts about what it sets out to prove. I think the researchers deserve a fair bit of credit for their work on this one.
David Aiken
I think the study provides evidence that there is no logical reason to limit frequency response of any recording medium to 20kHz., even if no one could hear above 20kHz.Unlike bass frequencies, treble over 20kHz. is:
(1) Not felt by the body
(2) Absorbed faily well by air in the room, and
(3) Easily masked by much higher music energy levels at other frequencies.As soon as I noticed that the study used unusual music that contained an unusual amount of high frequency energy, I suspected the study leaders had an agenda.
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Richard BassNut Greene
Subjective Audiophile 2007
"They are if the study is to correlate with people visiting this website and the typical music they listen to"To paraphrase Carly Simon, "You're so vain, you probably think this study is about you".
Why should this study correlate with people visiting here and the music they listen to? For a start, science is rarely concerned with audiophiles and music lovers. We benefit from quite a bit of scientific research but that's a happy accident. I doubt Oohashi and his fellow authors have even heard of us, and that doesn't detract from the study one bit.
I think that really drags this thread to an end.
David Aiken
Give me a $#@%&$@ break!
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Richard BassNut Greene
Subjective Audiophile 2007
Give you a break because the study results were used by someone here to support the purchase of supertweeters by someone else here!I'd be happy to give you a break if it weren't for one thing. Your first post was entitled "Dumb Study" and simply rubbished and, in my view, misrepresented some aspects of the study. I said I didn't think the study was so bad but all you've done since then is to try to trash it even further. You didn't about the use others made of the study at any time. You simply trashed the study at every opportunity.
I'd be happy to give you the break you asked for, for the reasons you want it but regardless of what others have said in this thread, my debate with you has never been about whether or not the study could be used to support the purchase of supertweeters. It's been about the general worth of the study, as a scientific study, right from my first response to you.
David Aiken
Amen.TL
"IF (note: big "if") you want to find out whether HF content can be perceived by listeners in some way (note: I did not say 'heard' for reasons I will state a little later), then I think as an initial test it is more than reasonable to start with subjects who are under 35 and largely female, and with music with a high HF content, because if you can't get a positive result under those circumstances you would seriously need to consider giving up on the hypothesis."This is simply starting at one extreme of possibilities to give the "best case" set of conditions. I see nothing scientifically invalid at all with those and I am not sure why RBNG thinks these are biases.
It also seems to me that brain activity is a much better indicator of whether someone heard a difference than simply asking them, which can be full of bias. Involuntary responses are most likely more accurate indicators.
As to FM, I am not sure why RBNG decided to muddy the waters with this comment. Since no one has ever heard FM with content ABOVE 15Khz then who is to say whether people would like it better or worse than with that content? Most people prefer cd or lp to FM radio in a high res system, is this because of more HF content?? Who knows.
Thanks for bothering to sum it all up.Oohashi & co. did another study in 2006 in which their findings seem to suggest that this HF content perception "occurs" not through the auditory ear mechanism (air pressure through ear canal etc.) but through some other mechanism, as you surmise yourself, too. When listening was done through high-isolation earphones, no such "hypersonic effect" was shown. When the whole body of the listener was exposed to the signal (through loudspeakers), the effect was there.
For some time already there have been speculations (and more serious studies perhaps too) regarding perception of sound through bone conduction.
TL
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