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General speaker questions for audio and home theater.

Re: Frequencies below 15kHz. mask the audibility of frequencies above 15kHz. assuming they are audible at all

"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


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