Very High Frequency Response: Does It Matter? -- A Data Cache
Tom Martin -- Sat, 03/27/2010 - 11:46
There is some debate about whether reproduction of sound above 20khz (the nominal limit of human hearing) matters. While working on another article, I found a nice analysis of the frequency spectrum of a cymbal when struck in various ways:
http://www.e.kth.se/~e92_aan/misc/
(click on musak.pdf)
I'm interested in other data on instruments, hearing, and audio reproduction at very high frequencies, and invite users to post links to published analyses.
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Interesting, Tom. Some years ago James Boyk published this this article
Brian Walsh
Essential Audio ~ Chicago area ~ 773-809-HIFI (4434)
'The experimenters found that the listeners' EEGs and their subjective ratings of the sound quality were affected by whether this "ultra-tweeter" was on or off, even though the listeners explicitly denied that the reproduced sound was affected by the ultra-tweeter, and also denied, when presented with the ultrasonics alone, that any sound at all was being played.'
Mildly interesting but forgetting 'subjective ratings of sound quality' surely a blind test would hav ebeen useful here - can they actually hear a difference. Seems like the kind of so called blind tests that some magazines do! So they can't actually discern the HF even though EEG showed otherwise. Perhaps the EEG is picking up the sound or the sound is being conducted into the brain and picked up directly. Does not mean it is actually discerbable in hearing.
The mechanics of the ear is what limits the human hearing range as can be seen with older people who have degraded ear mechanics. In which case the ear acts like a low pass filter. So if we are talking about hearing (through the normal route) then it would seem that ultra HF can't be heard, even if the instrument does produce it to some degree, special microphones and speakers are able to relay it and the recording medium is HD. Can the addition of ultrasonics improve the rest of the spectrum - quite simply no. Signal theory dictates that even if we play a near perfect square wave (utrasonic harmonics), the highest frequency component the human ear can possibly pass is around 20KHz so it no longer represents anything like a square wave - the inital transient is limited by hearing, not the equipment.
Kevin