That’s actually a nice graphic.
This is by definition not true.
I do think it depends on the instrument for sure. Anybody that has stood next to a pipe organ too closely can attest to that.
Yes, standing TOO close (to probably the reed family somehow), so that you don’t get the whole note as it was intended.
To hopefully shed some light on the original question:
My best educated guess:
They want to show you a graph with the full theoretical hearing range for humans (20hz-20khz). At the same time they want to emphasize not only range in which you hear fundamentals, but also the range where it is meaningful for you to look at an FR graph (which is up to 10kHz). Between 10-20khz is just a rough estimate, perhaps having something to do with, as alluded to above, the equipment they use to measure. But it’s clear from the graph they de-emphasize 10k+ regardless, and for good reason.
This relates to your EQing and a few other comments…
Under 10kHz you can look at things called “Equal Loundess Contours” which tell you, at various objective loudness levels, how loud you subjectively hear the sound at various frequencies. Basically a FR graph for your ear, each line being a given objective loundess level.
Research shows that under 10kHz the chart is meaningful: you can approximate the contours with a smooth line, and their distance from one another is fairly uniform.
Not so above 10kHz. Above this point, hearing is highly irregular and it’s difficult to establish clear correlation between objective loundess, frequency, and perception. You can imagine equal loudness contours suddenly crossing one another or violently going up and down.
For example, say you set your EQ to boost 14khz a few dB at a given listening level for a particular note and you’re happy with it. As soon as you turn the knob on your amp up or down a good amount, you have effectively changed your intended EQ setting at that frequency because your ear’s response to the objective loudness change is not as predictable between 10-20khz. Similarly if you hear the same note but an octave above with your EQ applied; you may hear it as “sharper”, you may hear it as “now ear piercingly sharp”, or you may not notice a change in sharpness at all. All because of overtones in the 14k range.
So I guess the take home point, based on theory alone, is: EQ above 10kHz is a crapshoot.
Judging by many of the posts I see on forums, this theory has plenty empirical support.
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