Talk:Dolby noise-reduction system

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Untitled[edit]

You can always listen to a dolby tape on a not-dolby compatible (i.e. linear) tape deck - how is that possible? The material should sound awkward, but it doesn't. Is there something like backwards compatibility implemented in Dolby NR technology? Thanks, --Abdull 20:12, 10 Jun 2005 (UTC)

Dolby B simply compands the dynamic range of the audio to reduce noise. See Companding, if it's still unclear.

I also disagree with the use of Companding as a catch-all term for Dolby NR. Dolby is more of a pre-emphasis system while dbx is heavily companding based.
Actually, Dolby B isn't quite as simple as that. For one thing, it is frequency-dependent, operating principally above 5 kHz. It also doesn't really compress the dynamic range per se. By improving the signal-to-noise ratio during recording, the net effect is to more closely preserve the dynamic range of the original recording. Without decoding during playback, the signal will contain boosted high-frequency information (including tape hiss). It is still listenable—and may even sound better than decoded playback unless the Dolby tracking is accurate, which it often isn't—but it will contain surplus high frequencies and noise.Rivertorch 02:42, 7 October 2006 (UTC)
To the trained ear* a Dolby B recording played on non-Dolby B equipment would sound distorted, though people with trained ears would be using equipment with noise reduction, or more likely hand-tweaked record decks connected to industrial speakers via solid gold cables. *(probably if a normal person compared the playback with and without NR, they'd notice the difference as well as the extra noise) boffy_b 01:35, 6 January 2006 (UTC)

Can someone write a description of Dolby S noise reduction as used on domestic cassettes.

Dolby S was not used on US domesitc cassettes in the pre-recorded market. Lots of reasons behind it. Mostly because Dolby B was out first and was able to gain market acceptance, it was also the cheapest and easiest to implement. Dolby B tapes also didn't sound as bad when played on non Dolby playback systems, unlike C or S which tend to sound off without thier respective systems. Some places issued tapes in Dolby C and i imagine possibly Dolby S, but most of these were special orders from places specializing in audiophile releases, but they were never mass distributed. Most recordings using C or S are indviual recordings.DewDude 16:58 06 Oct 2006

Is Dolby SR noise-reduction (for professional audio recording) the same as the SR-encoding used on 35mm motion picture (film) prints? Can this be mentioned in the main article?

Before Dolby Digital, DTS, Sony SDDS, most "Dolby-Stereo" (cinema surround sound) soundtracks were distributed on the 35mm optical print, encoded in Dolby A (I think.) Sometime in the 1990s, Dolby upgraded their optical sound processors (for movie theaters) to support Dolby SR. —Preceding unsigned comment added by 67.127.228.164 (talk) 00:15, 19 October 2008 (UTC)

The description of Dolby HX Pro is inadequate, and describes tape bias more than Dolby HX Pro. Can someone expand please?

No, not really. The reason being that HX Pro was a system that dynmically modified the bias signal applied to the recording dependant of the incoming audio signal. Higher frequencies don't need as much bias to be recorded as they're almost liner to the tape already. It's not a noise reduction method by any means, just an improvement of the way the audio was recorded onto the tape which would have a positive effect when played back on ANY player. It's difficult to expand it any further. --DewDude 16:50 06 Oct 2006

The link "Commercializing the Dolby Noise Reduction System" is broken and I could not find the appropriate article on a search of the target website (or elsewhere). --87.114.10.157 16:17, 4 December 2006 (UTC)

Dolby E[edit]

This page should probably have a discussion of Dolby E, even thought it's not really a noise reduction system. jhawkinson 03:56, 24 September 2007 (UTC)

Dolby HX Pro description - there is a sentence that does not make sense[edit]

The following sentence in the dolby hx section does not make sense:

"With fixed frequency and amplitude high frequency strong signals the amount of bias signal needed is reduced."

What on Earth does that mean? No really, I can't even guess what is trying to be said in this sentence.

I can't edit the text myself because I have absolutely no clue what was supposed to be intended by this sentence. I don't think it's simply a case of missing punctuation - it's absolute gibberish.

I hope someone can rewrite it,

Thanks

Daniel —Preceding unsigned comment added by Dpolwarth (talkcontribs) 23:10, 17 April 2008 (UTC)

I fixed the sentence, but the entire article needs copyediting. I'll try to get to that later today, but I'm wondering whether the HX section really shouldn't have its own article. The article, which is misnamed in the first place because it's about systems (plural), has "noise reduction" in the title. Although HX and HX Pro can boost the S/N ratio slightly, they are not NR systems per se. Rivertorch (talk) 23:48, 17 April 2008 (UTC)

What makes even less sense is that HX Pro is not a noise reduction system (it even notes it at the start of its section!), yet it appears in a noise reduction article. Surely it should be split out? danno 19:54, 8 September 2009 (UTC)

Yes, HX Pro probably deserves its own article. (Fwiw, while HX Pro isn't a noise reduction system per se, it does improve the S/N ratio by permitting higher recording levels.) Rivertorch (talk) 15:58, 2 April 2010 (UTC)

Dolby A[edit]

About 25 years ago when as the engineer for a radio station, I read an article in a technical magazine on the history of the Dolby noise reduction system. It mentioned that the reason why the Doors 1st record has such a bright high end sound is that the Dolby playback settings were accidentally not turned on after the tapes had been encoded. The explanation given was that it was new technology at the time and a secondary recording engineer was not familiar with it. Timeline wise this seems plausible. Has anyone found any verification of this?22yearswothanks (talk) 02:43, 21 March 2010 (UTC)

Neutrality disputed tag[edit]

It is premature to say that analog recording is obsolete. Even some CDs are going back to analog remastering to try to improve their sound. Our latest auditions of music on Bluyray, mainly concert videos, indicate that there is still a wide gap between the actual music produced by real instruments and the digitally recorded rendition of these. Analog is still the most capable of the trueist reproduction of the music dynamics and spatial dimensionality, discounting the high SNR possible with digital recordings. Digital is mainly preferred for its convenience.(207.35.47.66 (talk) 00:01, 23 March 2011 (UTC)RVK, March 22, 2011)

The current version reads; In other words, Dolby NR is not becoming obsolete for analog recording, but analog recording itself is less prevalent as digital recording has become more widespread. This seems quite reasonable and factual without being POV or OR, regardless of one's opinion. Ubcule (talk) 12:29, 4 September 2013 (UTC)
The neutrality of the claim made on this talk page of 'analog superiority' is also in dispute. Blind controlled studies where the listener has no knowledge of the actual sound source have proven time after time that current digital technology, when inserted into a channel, is audibly transparent compared to a single straight analog channel when playing a live performance in an isolated room at comfortable listening levels (actually the studies proved this with CD-audio digital technology that is 'inferior' to current technology). Claim of 'analog superiority' is only encyclopedic in the analog-vs-digital article on the (dying) controversy and is now widely recognized as fallacious.CherylJosie (talk) 20:56, 4 November 2013 (UTC)

'Spectral Skewing'??[edit]

The Dolby C section refers to audio 'spectral skewing' but links to a Wikipedia article on gas chromatography where spectral skewing refers to the change in detected mass spectrum due to the destruction of some (lighter?) components from the ionization(?) process. I suspect there may be another form of 'spectral skewing' that refers to audio spectrum or some similar term such as 'spectral masking' etc. but the link to mass spectrometry is obviously wrong. Does anyone know what the correct technical explanation is? CherylJosie (talk) 20:01, 4 November 2013 (UTC)

I removed the offending bit because the entire sentence was opaque and baffling. It was supposed to be informing the reader about the technical basis for Dolby C but it revealed nothing and just caused more questions. Binksternet (talk) 20:54, 4 November 2013 (UTC)

Dolby B controversy[edit]

There is no discussion about the belief that Dolby B "dulled" the sound. About 30 years ago, I ran uncontrolled tests using a Nakamichi NR-200 simultaneous encode/decode Dolby B/C processor, and a similar dbx II processor, without a tape recorder in the path. I convinced myself that the claim was correct. Dolby B slightly "dulled" the sound, while dbx had no apparent effect. I have a theory as to why this occurred (Dolby's clipping of overshoots during recording caused incorrect playback decoding). Of course, now that Dolby and dbx are effectively obsolete for tape recording, what difference does it make? WilliamSommerwerck (talk) 20:57, 21 March 2014 (UTC)

If you wanted to add something about this issue then you would need to refer to previously published sources rather than your own experience. Unfortunately, much of the 1980s audio engineering literature is still not digitized, so you would have to study the magazines and journals in archives where they can be found. Coincidentally, Dolby Labs in San Francisco has a huge library of such magazines and if you make prior arrangements with them, you can spend a day reading there. You might not want to tell them exactly what you are after. Binksternet (talk) 23:09, 21 March 2014 (UTC)
Agreed. One person's opinion doesn't count for much. Dolby B's defenders suggested that reducing background his made the sound subjectively less-bright -- which is why I tested without a tape recorder in the path. It isn't practical to visit SF, and I have no idea where I would start searching. (I just did a quick Googling, and found the only references to Dolby B dulling the sound were related to incorrect setup -- which was common.) WilliamSommerwerck (talk) 13:50, 22 March 2014 (UTC)
Yes, Paul White wrote in 1997's The Sound On Sound Book of Home Recording Made Easy that "Dolby B is often accused of sounding dull on domestic hi-fi cassette decks, but I suspect this is largely due to poor machine alignment or a failure to both record and play back using Dolby B." My own experience of dull sound is from the alignment of the recorded cassette being a little bit different than the alignment of the playback deck, especially with Dolby C which was more finicky. This is supported by a 1994 review in Stereo Review magazine which said "All too often, response or azimuth variations between decks cause the Dolby systems to magnify or dull the highs..." I don't know the author or article name.
Getting back to your experiment, I don't think I've ever read a review of Dolby B in which the reviewer listened to a purely electrical signal path, without transduction to magnetic tape. Binksternet (talk) 17:24, 22 March 2014 (UTC)