differences in white noise from pink?

[travisc]

I just got my avia disk and went through it. When I set my channel balances with white noise then look at them again with pink noise they vary. Especially between my forte II and my academy, like a 4db difference. can some one give me a rough Idea why this is and whether I should set them with white or pink?

[MrMcGoo]

Pink noise exercises the speakers over their full bandwidth, 20 Hz to 20 kHz. Your movie DVDs are mixed with speakers set with pink noise. Pink noise should be used with capable speakers like big floorstanders. Engage the crossover, but turn the subwoofer off while setting levels. Be sure to turn the sub on again afterward.

White noise is for less capable speakers and is more narrow in the frequencies covered.

I get much better results with pink noise on RF-7s, RC-7 and RS-7s.

Bill

[dragonfyr]

In the same way that the color white is a combination of all colors, white noise is a combination of all of the different frequencies of sound. White noise is the term for a broadband noise signal whose level does not vary with the frequency. It contains all frequencies, like light reflected from a white colored surface.

White noise exhibits a flat spectrum. Since the bandwidth of an octave (or third octave) becomes progressively wider by doubling the width for each octave, the use of white noise will cause the total energy content of a given octave to be the double of the energy content of the octave preceding it.

The excitation signal used is normally pink noise, employing broad band, or octaves, or third-octaves.

Pink noise is broadband noise with a spectrum whose level changes by a factor of 2, or -3dB/octave as the frequency increases. The amount of energy per octave will then remain constant since 2x0.5=1. It is called pink noise because it represents a deviation from the absolute flat spectrum (the white noise), just like pink represents a deviation from the color white.

Pink noise excites all frequencies. Using pink noise to stimulate a system to within a few dBs of regeneration allows the room and the sound system to display which frequencies are unusually sensitive to approaching regeneration (feedback), including those due to phase as well as amplitude.

[MrMcGoo]

An understandable discussion on how to set speaker levels with full spectrum pink noise can be found in this thread on the S&V forum: http://www.soundandvisionmag.com/idealbb/view.asp?topicID=37023&pageNo=1&num=20

Bill

[travisc]

thanks guys, I got some homework to do.

[Yesfan70]

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On 6/2/2005 11:05:47 PM MrMcGoo wrote:

Pink noise exercises the speakers over their full bandwidth, 20 Hz to 20 kHz. Your movie DVDs are mixed with speakers set with pink noise. Pink noise should be used with capable speakers like big floorstanders. Engage the crossover, but turn the subwoofer off while setting levels. Be sure to turn the sub on again afterward.......

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The AVIA disc does have a 5 speaker pan optional with a 150Hz HP option. This should eliminate the necessity of having to turn the sub on/off when setting the main channel levels.

[steelie]

About 7 or 8 months ago I was having a hard time balancing the bookshelf speaker I use for my right rear surround. First off, the speaker just sounded totally different from the rest of my set up. Second, my SPL meter kept telling me the speaker was in balance with the rest of the system despite the fact that my ears kept telling me it wasn't. For about a week, I attributed the discrepancies to the acoustics of the room, faulty ears and maybe some bad measurements. So, I kept testing and testing.

Finally, I started using both pink noise and white noise and found that while one test showed me the speaker was in balance, the other told me the speaker was about 4db lower than the rest of the speakers. (Can't remember which was which)

I took the speaker down, checked my connections and discovered the plate that acts as a biwire jumper between the binding posts had come loose and was disconnected. I was missing a whole segment of sound.

At the time, I found it strange that white noise and pink noise would produce such different measurements. After all, one was able to identify the fact that a whole segment of frequencies was missing while the other went on as if there were no problems. Curious.

[kelA]

So with that in mind; what do most receivers employ for their test tones? White or pink noise?

[sfogg]

" what do most receivers employ for their test tones? White or pink noise?"

Usually neither. I believe most will employee a band limited noise usually covering something like 250hz to 2 or 3kHz.

That helps match the midrange area better and will avoid artificial readings from room boom or from speakers that have greater bass response then others.

Shawn

[dragonfyr]

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On 6/3/2005 1:42:47 PM kelA wrote:

So with that in mind; what do most receivers employ for their test tones? White or pink noise?----------------

My first question would be: "test tones for what purpose?"

If it is for the purpose of 'flattening composite (non-minimum phase) signals' - the 'room response', its time to once and for all address the "what can EQs equalize?"! And EQs cannot correct for non-minimum phase room response. They simply change the phase relationships of the composite direct sound components via the use of the LC components and effectively move the resultant polar anomalies of the summed signals around slightly. They can ONLY EQ the direct signal from a speaker (and even then they cannot resolve non-minimum phase issues between drivers!!! And if a parametric EQ is employed, they can only minimize the overlap of the adjacent passbands through the use of high/infinite slopes.)

I understand how folks new to the topic believe that EQs can do marvelous things, but it is important to understand that their effectiveness is actually very limited (and limited to a particular 'situation'). Once this is understood, perhaps we can move ahead on this forum to discovering what CAN effectively be done. But this topic seems to live on forever, much like the infamous cable debates, unfortunately without much of a cumulative increase in forum understanding!

And the resurgence by manufacturers of the use of test tones to 'calibrate the room response' is one such ridiculous solution literally worthy of the same engi-, I mean, marketeers at Bose who brought you 'direct-reflecting' un-intelligibility!

Secondly, with the non-linear energy content of white noise, it is useful for little more then synthesizing a snare drum (and for those not familiar with this real studio technique, you might be very surprised!).

If you have a use for 'noise', and rap won't fill the bill, you would generally want to use pink noise for its energy envelope weighting correction.