What sound is in the 15K and up range?

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Projbalance

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I noticed that Soundforge has a preset for shelving all frequencies over 15K. When I play with this I generally notice a certain dullness is removed from the tracks, which I thought was the oppisite of what should have happened. Being a cumulitive effect, the more times I have applied it to the same track, the less dull they sounded. What is really happening when I do this? The waves look as though the energy is being re-distributed into the track, but I don't understand how that happens.
 
It sounds like it's increasing the frequencies over 15k, thus making things brighter.
 
What I'm doing is cutting all the frequencies above 15K, just completel killing them. This is my question becaue I cannot understand how completely cutting everything above 15K makes everything else sound brighter. My only reasoning is that energy that is no longer being used for attempting to produce sound in those frequency ranges is now being diverted to other frequencies. I just don't know if this is somethign that I want to do for the most part.
 
There is very little above 15k. No standard instrument or voice can produce fundamental tones that high, and most musicians (and probably much of the general public) can't hear very well up there, anyway. Most inexpensive speakers don't reproduce much in that range, either.
 
That's where the "air" in a mix is....... and you want to be careful with any boosts or cuts in this area - adjustments in that freq band are usually only fractions of a dB (quarter, half, three-quarters)... :cool:
 
Can you check the Q setting that the Soundforge preset uses? If it's too high, your high-shelf filter will actually introduce a boost at around 8Kz. The image I attached should help visualize it. I suspect that's what's going on, since a boost at 8Khz would definitely make a track sound brighter.

If you want to just trim everything above 15Khz, you should use a low-pass filter.
 

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Scrubs and noissewreck are both basically correct. I have to wonder if this is one of those "when you know everything is right, but the answer still comes out wrong, something you know is right is actually wrong" instances. ;)

If it's not; if we take the case at face value, then I'd have to ask how that could theoretically be and what's causing it. So this is just theoretical specualtion, but perhaps something along the lines of...

A hypersonic noise in the 15-20kHz range is coming from somewhere (electronics RFI? colored microphone? commie satellites?) and being recorded. This noise itself is mostly inaudible, but it has a first-level subharmonic that is phase interfering with some good, bright stuff in the 7.5 - 10kHz range.

You got a spectrum analyzer? If so, what is it showing above 15k before you put up the shelf? Any annoying bumps up there? Or if you don't have an RTA, you could sweep through the uppers with a parametric EQ to see if you can slot out a particular offending frequency.

If you can ID a particular culprit frequency, that might help ID the source. And you really want to ID the source, because shelving all that stuff is normally not a great idea - expecially if you have quality mics and pres that can actually deliver the good "air" that can be found up there.

Just some semi-educated guessing...

EDIT: Just read DM1's post. I'm going with that for now. Nice call, DM1 :).
G.
 
Man, do you realize how much work has gone into giving you gear that accurately reproduces that high frequency content, all for you to shelve it out? Oh, the humanity! ;)
 
scrubs said:
There is very little above 15k. No standard instrument or voice can produce fundamental tones that high, and most musicians (and probably much of the general public) can't hear very well up there, anyway. Most inexpensive speakers don't reproduce much in that range, either.
Click to expand...

yes but the upper harmonics are what differentiates a violin from a trumpet. the most expensive gear usually goes to 40,000 hz and higher.
 
Blue Bear Sound said:
That's where the "air" in a mix is....... and you want to be careful with any boosts or cuts in this area - adjustments in that freq band are usually only fractions of a dB (quarter, half, three-quarters)... :cool:
Click to expand...

i bet in a blind test you couldn't hear a half a decibel adjustment.
 
FALKEN said:
i bet in a blind test you couldn't hear a half a decibel adjustment.
Click to expand...
I'll take that bet.

It's not just a single half-dB adjustment, Its shaping the sound up there a half-dB here, a dB there. You wind up with a curve not unlike the difference in curves between a U47 and a B1. Definitely an audible difference.

Unless your money is in worthlesss Cuban script, I'll be glad to take it. :)

G.
 
FALKEN said:
i bet in a blind test you couldn't hear a half a decibel adjustment.
Click to expand...


a 1/2 db at 17K ?

maybe some people could hear it, but not most people.
 
SouthSIDE Glen said:
curve not unlike the difference in curves between a U47 and a B1.
G.
Click to expand...

i'd be willing to bet that in the 15K and up area the differences between a
U47 and a B1 (i'm assuming SP) are much grater than 1/2a db.
i don't know that for sure, i'm just guessing.
maybe worth looking into.....
 
FALKEN said:
i bet in a blind test you couldn't hear a half a decibel adjustment.
Click to expand...

One signal that is in that range is dither, more than 1/2 decibel, but if you totally cut the ultrasonics, so goes your dither.

mp3s will typically cut everything over 16kHz. I don't know exactly why the algorithm does that, but it doesn't enhance the sound quality any.
 
FALKEN said:
yes but the upper harmonics are what differentiates a violin from a trumpet. the most expensive gear usually goes to 40,000 hz and higher.
Click to expand...

BWAAAAAAAAAAHAHA.

That is all, please continue.
 
FALKEN said:
i bet in a blind test you couldn't hear a half a decibel adjustment.
Click to expand...
If you can't hear a half dB EQ adjustment - you have no business behind a console!
 
Blue Bear Sound said:
If you can't hear a half dB EQ adjustment - you have no business behind a console!
Click to expand...

Luckily most really good engineers continue on anyway!

:rolleyes:
 
DM1 said:
Can you check the Q setting that the Soundforge preset uses? If it's too high, your high-shelf filter will actually introduce a boost at around 8Kz. The image I attached should help visualize it. I suspect that's what's going on, since a boost at 8Khz would definitely make a track sound brighter.

If you want to just trim everything above 15Khz, you should use a low-pass filter.
Click to expand...

That explanation actually makes the most sense. I don't have really great gear, just ok, so I'm not sure what I'm getting up that high in terms of ultra sonics and harmonics, but the possibility of an 8K bump coming off the shelf would explain a lot.
 
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