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Old 5th February 2013, 09:22 PM   #34261
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Christophe,
It just seems if you can get the phase shift and group delay across the band correct everything starts to sound clearer. Perhaps this along with the instantaneous leading edge of the bass gives the impression of better bass. Obviously we are not increasing the air movement or anything else in the bass region by adding upper frequency response, perhaps it is the higher frequencies that let us tell a kick drum from a kettle drum. There is more to the sound of the drum head than just moving air or we would perceive all drums the same.

As far as engineers liking it here better than in France that may be just the tax rate that helps there? Besides we have great baguettes and cheese here now, food always helps!
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Old 5th February 2013, 09:24 PM   #34262
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Quote:
Originally Posted by Kindhornman View Post
Can somebody explain to me in plain English how dither, adding noise to a signal lowers the noise floor when reducing the bit rate?
Dither adds (a little) noise, but its use preserves information below the LSB level. Our critical band hearing then allows us to hear some of that preserved information, just as we would in the presence of the same (small) noise in other circumstances.

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Old 5th February 2013, 09:39 PM   #34263
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Quote:
Originally Posted by Kindhornman View Post
Can somebody explain to me in plain English how dither, adding noise to a signal lowers the noise floor when reducing the bit rate?
Plain English will be the problem.
Well, let's give a photographic example.You know this color banding you get on a digital captor using Bayer's matrix when there is in a landscape a repetitive pattern near the captors photo-sites spacing ? Adding an optical *noise* (AA filter) at those frequencies will blur the patern and prevent those artifacts.
Same thing for a signal when it is just at the limit of a bit: the Dither will bring-it sometimes to the upper one, sometimes to the lower. if it is the last one, you will keep something, instead of a brutal cut.
When you reduce the bits number, by dividing, you create an error (rounding). Noise will random this error in a more natural way.
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Last edited by Esperado; 5th February 2013 at 09:46 PM.
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Old 5th February 2013, 10:00 PM   #34264
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Here's a link I post regularly when people who don't understand digital start pontificating. It's a clear and highly demonstrative look (and listen) at dither, and I am jealous that Werner did it and I didn't!

That Dither Thing - [English]
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Old 5th February 2013, 10:14 PM   #34265
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yep that was the example I was going to use, with offset and screen printing, you can with a half-tone screen, get what is called a Moire pattern when when the colour separations are out of alignment (error), or if you make a half-tone of a half-tone (for example by scanning and reprinting a printed page). we can think of this as our audio resolution in an imperfect system, some of these 'dots' will create interference patterns because they start out regular.

to combat this, high resolution inkjet and even high quality high end printing technique uses Stochastic screening, which is a sort of dithered imaging technique.

Moire
Click the image to open in full size.

Last edited by qusp; 5th February 2013 at 10:20 PM.
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Old 5th February 2013, 10:25 PM   #34266
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This one is funny too: it is a file with one white pixel, one black pixel. You can play with the zoom and see what happens:
Charte gris neutre
The original file is supposed to be just neutral grey.
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Old 5th February 2013, 10:30 PM   #34267
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Originally Posted by Kindhornman View Post
Since we are so ot here let me ask a question. Can somebody explain to me in plain English how dither, adding noise to a signal lowers the noise floor when reducing the bit rate? I have read some of the information that George has presented and am having a time of understanding the principal here. A serious question as it seems so important to using some of the digital volume controls and other things in the digital world.
Noise floor I don't think is the right concept to understand dithering.

What in my conceptualization happens, is that with small signals, coded with only a few bits, the steps become quite large compared to the signal itself. Without dithering, these individual steps would become a subsignal on their own (they are correlated), creating audible distortion. With dithering, the individual steps become randomized because the noise introduces random variability in the trigger point of the ADC. So, the individual steps do no longer produce a correlated signal of their own. The only thing perceivable that survives is an approximation of the original signal, because the peaks and throughs of the original signal will remain.
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Old 5th February 2013, 11:04 PM   #34268
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Thank you everybody for the response. Hopefully I am not the only one wanting to know about this phenomena. Qusp, as soon as I saw your example I remembered this from my graphic arts classes. Been a long time since I thought about that.

Steven
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Old 5th February 2013, 11:10 PM   #34269
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Originally Posted by Kindhornman View Post
Can somebody explain to me in plain English how dither, adding noise to a signal lowers the noise floor when reducing the bit rate?
If the noise floor of MANIPULATED, but undithered signal contains distortion components, these components indeed might be higher in amplitude than the same (manipulated) signal with added dither.

http://www.users.qwest.net/~volt42/c...rExplained.pdf

Note. I think Nika used Spectrafoo's Accumulation Mode setting "Pink noise is flat" in his measurements. This is why spectragraph plots look as if noise is rising towards high frequencies.
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Old 6th February 2013, 12:16 AM   #34270
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About noise floor, as natural acoustical noises witch comes with the recordings is always a lot higher than the noise you can add with dither, there will be no negative impacts in real world.
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