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The importance and effect to and above 20kHz...

Hi Everyone -

I was wondering if anyone would care to elaborate on the importance of system frequency playback as the frequency range approaches and passes 20kHz. What effect does 15kHz have on music, for instance, and why is it important to keep the upper frequencies as linear as possible? How about 18kHz, or 20kHz, or 25kHz? What effect can these specific frequency regions have on the overall performance, and why should I keep them linear?

Let me clarify, I used those particular frequencies as examples, but if they can be expounded upon, then go ahead. I'm hoping everyone understands what I'm trying to get at. What effect can the upper treble frequencies have and why is linearity in these regions so important? Same goes for above 20kHz, say in the 22-30kHz region.

Can anyone explain?

Thanks for you help.
cdwallace
russschaeffer
34 posts
 
It's not important to me at all in my right ear, I can't hear the crickets in that ear anyway but if a system goes to 20khz and past it's a good indicator that the audible high frequency performance will be good. Systems that only claim 15 khz usually sound rolled off on the top end.

Thanx, Russ
shadorne's avatar
shadorne
7,477 posts
 
I am not aware of any evidence that frequencies beyond audibility (around 15 KHz for most of us) have any relevance at all. The basilar membrane is a band limited device and can't resonate enough above 20 KHz to generate any neural discharges to the brain.
cdwallace OP
216 posts
 
So then...I guess my next question would be...how important is it to build a system around the >20kHz factor, so to speak?

If there are any benefits, be it small or great, are these added benefits substantial enough to warrant building a speaker around them? For instance, 99.5% of todays electronics are capable of transmitting signals above 20kHz, most about 50kHz. This covers the CD Player, Pre/Pro, Amp and even cable sections; which leaves the weakest link...the speakers. Some claim but few produce over 22kHz. Even fewer over 25kHz to 30kHz. Mind you, >20kHz is inaudible, but it adds the "air" to the recording. Is this the only benefit and should a system be built around it?
cford
66 posts
 
While we can't hear above 20khz, any sound content above 20khz could interact with other sounds and the resultant interaction create sound that are the difference between the 2. For example, 20hkz and a 22khz interacting together would create a 2khz beat freq. Whether or not there is enough energy in this signal that could affect the hearing would be difficuilt to say.
shadorne's avatar
shadorne
7,477 posts
 
For example, 20hkz and a 22khz interacting together would create a 2khz beat freq. Whether or not there is enough energy in this signal that could affect the hearing would be difficuilt to say

Good point. Not many people are aware that we can't even hear proper waveforms above 4 KHz....the ear's nerve bundles fire too slowly! In order to hear above 4 KHz the brain relies on two things; beat frequencies and differences in timing of what arrives at one ear versus the other.

However, very low signal amplitude because the basilar membrane does not vibrate enough to transfer energy to the inner ear at higher frequencies impies that you can't even hear beat frequencies for signals with frequency content higher than 20 Khz (or 15 Khz for most of the older folks).
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