I believe pink noise, and white noise, are first of all random noise, like hiss, used for testing electronics and acoustics. I think that pink noise is equal enery per ocatve and white noise is equal energy per decade. For example, pink noise would have the same energy in the 20Hz to 40Hz range as there is from 40Hz to 80Hz. White noise would have the same energy from 20Hz to 200Hz as there is from 200Hz to 2,000Hz. I am sure someone else here can give a better explanation. Please help! |
Blueswan sounds about half-right. Pink noise has equal energy per octave. White noise has equal energy at all frequencies.
One virtue of pink noise is that it's an easy way to test frequency response. It's much easier to hear differences in frequency response when listening to pink noise than when listening to music. That's because, in music, there might be little or no energy in the frequency range where the difference occurs, or what energy exists is masked by louder sounds at other frequencies.
On the other hand, pink noise would be a lousy way to test transient response or imaging! |
i assume that it's a noise of a pink freequency spectrum. pink is a composite color from red, blue; blue is at the same time is composite color of RGB of a certain intencity. white freequency is usually the composite of all colour freequencies of a highest intencity together.
if we assume that the colour freequency is someway proportional to the audio freequency we can make judgements about the noise behavior in terms of colours.
there can also be maroon, burgundy, yellow, bage, ultramarin, off-white, cyane, navy-blue,... etc... noise.
to tell you the truth i don't yet recognize the noise colors and probably i will need to smoke a joint or do something more serious to realy distinguish ultramarin from for example bage types of noise.
dig it? |
Pink noise is equal energy at any given octave. White noise is equal energy at any given frequency.
The result is that white noise sounds more like high frequency noise, and pink noise sounds like full range noise.
Think of it this way. An octave represents a doubling of frequency (40Hz is an octave higher than 20Hz. 14,000Hz is an octave higher than 7000Hz etc.)
As you look at that, think about how many more frequencies are contained within any given octave as you go up the musical scale.
Concert A (a minor third below middle C on the piano) is equal to 440Hz. The lowest note on the piano (excluding some Bosendorfers) is three octaves below that, or 55Hz. If we count in whole integers, there are only 385 frequencies between those three octaves. Three octaves ABOVE concert A resonates at 3,520Hz. If we count in whole integers again, there are 3080 frequencies between concert A, and the A three octaves above it.
If each one of the 3,465 frequencies implied in the above paragraph has the same power when they are all played at once, we will hear the higher frequencies as being louder, because there are more of them per any given octave as you go up the scale. White noise
If you devide up those frequencies into octaves, and compensate for the doubling of energy that is inhearant in white noise by giving as much energy to the octave between the lowest note of the piano ((A1-A2) 55-110Hz) as you would to the higest octave of the piano ((C7-C8) 2093.04 - 4186.08Hz,) you get Pink Noise.
hope this helps |
the name pink noise comes from the fact that the noise is skewed with more power towards the low frequencies... i.e. the redish or pink equivelant in the visual spectrum.
White light has equal energy per frequency as well. |
Pink noise being equal energy per octave (or even more importantly equal energy per one-third octave) divides the frequency spectrum in a manner similar to the human ear. One-third octave spectrum analysis and equalization often results in a corrected spectrum that is generally pleasing perceptually (particularly in sound reinforcement applications). |
Ok, this is fascinating. Since we've gotten the attention of folks who genuinely know their stuff, I've got one more that's been puzzling me -- "brown noise."
I'd never heard of this before geting thay Ayre burn-in disk, which has tracks of white, pink and brown noise (as well as some full frequency sweep tones). What am I getting with the brown noise besides an apparently deeper yet tone from the pink noise and a whole lot more exercise for the bass drivers? |
is "brown noise" and fart the same thing? |
If you ever heard one of her albums, you would know. |
Alcides - your pink/white noise analysis is correct, but you're off by an octave on the piano's low end. The standard 88-key piano goes down to ~28Hz, also the 440Hz A is above middle C, not below. |
So if you were going to measure in-room frequency response, would you use white noise or pink noise?
And how do you measure sound at any particular frequency? Rat Shack SPL meter and Stereophile test tones miss a large part of the frequency spectrum. I would think using white or pink noise would be much more accurate - IF it can be done. |
Hearhere... whoops... atleast I got middle C right. |
261.63Hz if you do the math... Where's my drink? |
Cdc,
If you must use a broadband noise signal, use pink noise. White noise will be irrelevant. If you use a broadband noise signal like pink noise, you need to have a spectum analyzer to really be able to measure the in room response. These will generaly give you a graphic display with frequency on the x axis, and absolute level on the y axis. Much like the graphs we all see in Stereophile etc. Measurments of this type get tricky and expensive.
Stereophile's discs do miss much of the spectrum, but what they include are tones that actually apply to areas in your listening room that you might actually have realistic control over. They also assume the average listener is going to have a radio shack SPL meter that has poor frequency response in the low and high end. |
Thanks Alcides, this sounds too expensive / complicated for me. The more I get into this stereo stuff the more I realize it's practically impossible to figure it out - at least for me.
Anyhow I think I'll be getting a Tenma SPL meter, $119 from mcmelectronics and Rives Audio test cd. The Tenma is +/- 1.5 dB and hopefully better that Rat Shack. |
Thanks you all for your replies.
Regards! |
