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What is the maximum peak level of the recorded music at each octave band, ½, or 1/3 octave band (compared to 0dBFS)?
If I increase a specific band by 10dB, should I decrease the overall level by 10dB to avoid clipping?
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"What is the maximum peak level of the recorded music at each octave band, 1/2, or 1/3 octave band (compared to 0dBFS)?"The answer depends on the music signal. Many musical instruments have more energy in their second and/or third harmonic than in their fundamental. Instruments such as the flute have very simple overtone structures composed mainly of even-order harmonics. Others have very complex structures, and some have large amounts of odd-order harmonics. All of these variables affect not only the peak-to-average level, but also the frequency bands where the maximum energy level is located. Taking it a step further, the spectra of musical ensembles varies based not only on the make-up of the ensemble, but varies depending on the piece being played, and further it varies moment-to-moment.
"If I increase a specific band by 10dB, should I decrease the overall level by 10dB to avoid clipping?"
Again, it depends on the signal, but in general, the answer is "no". If you're boosting an upper frequency range which had been contributing very little to the overall signal level, then clearly the answer is no. But if you're boosting a range which already has fairly significant energy, you will likely need to reduce the overall gain "by some amount" in order to maintain headroom.
On a related point, the increase or decrease of a signal's level based on the raising or lowering of some frequency band also depends on the phase relationship of the component harmonics. As a simple example, take two sine waves of equal frequency but 180 degrees out of phase. Let's say they are each on their own faders. With one fader all the way up, and the other all the way down, you will have the maximum output level. As the second fader is raised, the level will actually drop because you are adding an out of phase signal, and they sum negatively.
hth
Edits: 01/11/09
"What is the maximum peak level of the recorded music at each octave band, ½, or 1/3 octave band (compared to 0dBFS)?"
I am also asking the dependency of the max peak level at a band on frequency. For example, is the peak level in the high end frequency band the same as a mid frequency band?
Hello Dave789,
What is the application and environment you are attempting to apply 10db to a single frequency in?
Our "other" rig sounds much better!!
Thanks for your reply.
The "10dB" and "one" band are not key points of my question.
Let me restate the latter part (the supplementary part)of my original post in a different way.
Suppose a graphic EQ and subsequent gears are operating just below clipping (and thus maximal S/N). If one frequency band (or a couple of bands) in the graphic EQ is increased by 4dB, should the input level control of the EQ decreased by the same 4dB to avoid clipping?
Paradoxical as it sounds, you may need to reduce the input level by more than 4 db. For example, if the input signal were a square wave and you were to boost the fundamental by 4 db and leave all of the overtones unchanged, the peak signal would end up being boosted about 5 db. (Verified by using audio editor software to generate test signal, perform EQ and examine peaks.)
Another way of looking at this would be to see what would happen if you were to leave the fundamental the same and reduce all of the overtones in the input square wave. At first glance you might think that the net result would have lower peaks, but actually, they would be higher. The reason this happens is that the original square wave was a combination of a louder fundamental that has been partially cancelled by the overtones. When you filter out the harmonics you end up seeing the louder fundamental. In the case of a square wave this amounts to a factor of 4 / PI , which is around 2 db. In your 4 db example, the harmonics are reduced, but not eliminated. The magnitude of this anomalous effect will depend on the input waveform. If the input wave form is a pure sine wave then there will be no anomalous effect and a 4 db boost in the selected band will result in a 4 db boost in the output.
While the example was constructed with an artifical waveform, this was just for simplicity. I first encountered this effect with a computer audio workstation when I got a clipping warning when I reduced the amplitude of some frequency bands on a previously unclipped waveform.
It is best to keep a few db of headroom to avoid these problems.
Tony Lauck
"Diversity is the law of nature; no two entities in this universe are uniform." - P.R. Sarkar
I think the answer to your question is yes. Boosting one frequency by 4dB will raise that frequency above the clipping level so the overall gain level should be reduced so no frequency is above the clipping level.
Agreed... just as you would reduce input gain on a mixer channel according
to EQ boosts on that channel.
However, a 4db frequency boost "often" reflects a problem or deficiency elsewhere in the signal chain.
Our "other" rig sounds much better!!
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