Talk:A-weighting
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[edit] Merge with weighting filter
[edit] Created the page
I created the page called A-weighting today with the intention of adding considerable detail about its used and derivation from the equal loudness contours, which I have also worked on.
I not agree with merging this with weighting filter because weighting filters are used for many things and should be covered more generally - as I have started to do. I would like to move all the detail on A-weighting to the A-weighting page, but leave a more basic description under weighting filter.
With this in mind I cross-linked several pages - noise, ITU-R 468 noise weighting, A-weighting, noise weighting, equal loudness contours and weighting filter to make it easy to find out more from each. Each of these topics is important in in its own right, and there is much to cover. As a designer of measuring equipment I find much confusion around these topics which I am trying to throw light on. Lindosland 23:29, 26 October 2005 (UTC)
[edit] Merge
Yes, definitely needs merging into Weighting filters. It cant really stand alone IMHO--Light current 18:07, 29 October 2005 (UTC)
[edit] New stand-alone article
This is a start, and I feel it can now stand alone on the grounds that it incorporates some useful information and graphs allowing comparison with ITU-R 468 and the latest ISO 226 equal-loudness curve from which it is supposedly derived. I will replace the first graph with one showing B,C,and D weightings later (I've finally mastered .svg log graphs which are ideal for this purpose.Lindosland 20:33, 30 November 2005 (UTC)
[edit] Partial merge still needed
It's inappropriate to have so much content from this article duplicated in the weighting filter article. If this article is to remain, then it should be the primary source of info about its topics; the weighting filter article should merely summarize and point to it with a {{main|A-weighting}} template. —mjb 23:03, 8 July 2006 (UTC)
[edit] A, B, C, D
So this article is called A-weighting, but covers all four letter-designated curves? It should have a more accurate title. Where were these curves standardized? Who created them?
This article has a lot of redundant content with Weighting filter. They should either be merged or the redundant content removed. — Omegatron 15:05, 3 January 2007 (UTC)
[edit] Factual inaccuracies
On the A-weighting page is written "For instance, noise shaping achieves the same distortion benefits as dither noise, but moves the noise to inaudible high frequencies. " The former part of that sentence is technically incorrect. For the latter part to be correct, it depends on a particular situation. I've worked some in the Audio field and was lucky enough to have worked at Benchmark Media Systems, Inc. (manufacturers of some of best Digital Audio converters in the world) where I learned that dithering is required for digital signal-based systems to work properly. I would recommend that you look at the dither related papers written by professors and grad students at the University of Waterloo, Canada -- see http://audiolab.uwaterloo.ca/papers.htm for links to papers. They are state-of-the-art when it comes to research into properly sampling and maintaining digital signals. The sonic difference between noise shaping and dither was shown to me in 5 minutes on Audio Precision ($20,000) test equipment. Noise Shaping alone will not eliminate audible distortion caused by quantization. Whether you noise shape or not, dither of the proper type (and the proper type is the key to making this work -- it can't be just any kind of dither) must be used to convert distortion from quantization error into audibly benign noise. What Dither (and the need for it) does to quantized systems has been formally mathematically proven, it's not just hearsay or someone's opinion.
As for the latter statement in the sentence, it depends on what processing follows the noise shaped signal, what kind of "filtering" (using the Flether-Munson curves for example) was performed by the noise shaping function, and what volume level the signal will be listened to (among other factors). It's been demonstrated in studios that if Fletcher-Munson curves are used to determine where to place the "noise", then by changing the playback volume, what was inaudible noise will become quite audible and possibly annoying. The annoyance is because the noise floor is no longer similar to white noise, but is now colored -- it can have a perceived pitch to it. --Ultimatesynth 02:08, 15 August 2006 (UTC)
