Topic: Dolby NR (Read 7528 times)

cascius · « **on:** April 15, 2004, 03:05:05 pm »

Hello guys,

I'm currently listening to Mozart - Moonlight Sonata, an amazing piano masterpiece, but I'm having a major problem with the quality of the sound. Even though the mp3 is at 320, there's a LOT of noise. I think that comes from the recording itself.

So i was wondering if there was a way to get the equivalent of a Dolby NR DSP/DirectX plugin. Also, if anyoneknows some good DirectX plugins in general, feel free to point me in the right direction.

It's a shame to listen to such a masterpiece with so much noise. It really takes a lot from the beauty of the piece.

-Cascius

JimH · « **Reply #1 on:** April 15, 2004, 03:09:15 pm »

There are a lot of things that can cause sound problems. A google search might find some but here are a few:

Make sure your microphone is muted in the Windows sound control. (speaker icon in lower right corner of desktop)

In the same place, make sure your system volume and wav level are set high if you're amplifying the sound after it comes out of the PC.

Via chipsets can cause problems. Google will tell you.

Sound card drivers sometimes introduce problems.

cascius · « **Reply #2 on:** April 15, 2004, 03:40:44 pm »

Thanks Jimh, the thing is though, that this noise just comes from the specific recording. All other mp3s play just fine. That's why I was wondering about a dolby ND filter or something like that. I might just trow that file in ProTools and clean it up. Dunno.

-Cascius

paulr · « **Reply #3 on:** April 15, 2004, 03:46:24 pm »

I'm not sure why anyone would make a Dolby NR DSP plugin. Dolby NR was only used for analog recordings on tape. It boosted the higher frequency ranges during recording, then attenuated them during playback. This effectively gave a much larger signal-to-noise ratio in the frequencies where tape hiss occurred. But, the piece had to be recorded using Dolby NR for it to not ruin the sound.

If this MP3 was made from a CD, then it is a problem with the source material and Dolby won't help you, unless you want all the high frequencies muddied out. You'd probably be better off cleaning it up with some sort of software as you suggested.

cascius · « **Reply #4 on:** April 15, 2004, 03:54:34 pm »

Thanks Paul, great explanation on how Dolby NR works. Yeah, I'm just gona have to clean it up manually, no biggy.

Anyway, what about some cool Direct X plugins? anyone know of any?

DocLotus · « **Reply #5 on:** April 15, 2004, 04:11:27 pm »

Dolby will not clean up a noisy signal.

What Dolby does is reduce the amount of noise from being added to an already clean source signal. It does this by increasing certain parts of the frequency spectrum level by 20 - 30 db as it is recorded thereby increasing the signal strength to the recording device such as magnetic tape. When the tape is played back the opposite happens, Dolby lowers the same exact parts of the frequency spectrum by the same 20 - 30db thereby lowering the noise threshold of the tape by the same 20 - 30 db. This makes a much cleaner & relatively noise free recording (assuming there was no noise added by the source material).

If the source material was, let's say, an old noisy vinyl record then Dolby will not add any more noise to the new recording but it can do nothing about noise that is already there. That noise will simply be passed along to the new recording as part of the original source material.

dBx works somewhat similar except it does a better job as it raises the whole frequency spectrum by 40db. Upon playback, it lowers the whole frequency spectrum by 40db. dBx when used on a very good tape recorder can produce tapes with S/N ratios approaching that of a really clean CD... 100db.

What you need is to locate a device (hardware or software) that will filter out certain types of signals. I had one years ago (hardware) that worked on record pops by filtering any sound that had a very fast rise & decay time. It was analog & had to have a threshold level set up for records depending on how bad & load the pops were; if the threshold was set to high it would degrade the overall sound. It worked, sort of, but was a pain to use. As I recall I sent it back.

Today there may be some digital devices that can do a better job. Not sure where to point you.

This may be more trouble then it is worth. Have you considered just buying a new (or used) CD?

paulr · « **Reply #6 on:** April 15, 2004, 04:25:53 pm »

I just googled "digital audio noise reduction directx" and found some interesting things.

You might want to look around. It looks like there are a lot of products available.

cascius · « **Reply #7 on:** April 15, 2004, 04:32:10 pm »

Thanks guys, I'm going to try sonic foundry noise reduction and let you know how that works.

xen-uno · « **Reply #8 on:** April 15, 2004, 04:46:40 pm »

Confessions X...

I used to make Dolby B tapes and would turn the noise reduction off on playback. Therefore I must ask...am I evil? weird? or just demented?

Alex B · « **Reply #9 on:** April 15, 2004, 04:50:52 pm »

Besides Dolby and dBx there was a cheap playback only filter construction, which was usually called DNR (dynamic noise limiter). That lowered treble level at quiet parts of music. So the high frequency hiss was lower too. When there was more audible treble in music the filter adjusted itself off, because the hiss was then covered by music. I don't know if there is any software version of it.

I have used Algorithmix Sound Laundry for rips from old vinyl albums and it can remove some of the noise (also scratches) without affecting sound.

DocLotus · « **Reply #10 on:** April 15, 2004, 04:54:14 pm »

Demented, definitely demented

Robert Taylor · « **Reply #11 on:** April 15, 2004, 05:03:19 pm »

Xen,

I used to do the exact same thing!

Recorded with it switched on. To my ear, switching OFF the Dolby on playback sounded okay, whereas switched on it seemed to lose way too much treble.

I also used to use Chrome and Metal tapes as they seemed to hold better treble.

Now I no longer use or even have any cassette tapes, my world is purely digital.

xen-uno · « **Reply #12 on:** April 15, 2004, 05:05:03 pm »

Thanks Doc...you've confirmed my suspicions...

paulr · « **Reply #13 on:** April 15, 2004, 05:11:42 pm »

Hah! I did the exact same thing. On the garbage equipment I had at the time, recording with Dolby, and playing back without sounded 'normal'. Even if I still used tape, I wouldn't have that issue anymore!

Thank goodness!

DocLotus · « **Reply #14 on:** April 15, 2004, 05:23:10 pm »

dBx made several great ones... 2bx, 3bx, & 4bx (among others). The difference between them was the number of frequency bands each had. I owned a 3bx, & still have a 4bx model.

dBx made units from only one range to 4 ranges. The 3 & 4 range units broke the frequency range into 3 or 4 bands & each part was handled separately which was supposed to eliminate a pumping sound that the single range units sometimes exhibited.

The way they worked was load passages would be made 50 percent loader, & quite passages would be made 50 percent quieter. This provided up to a 100 percent increase in the overall dynamic range of the music; if the original source was 60 db dynamic range (difference between loudest & quietest parts), it became 90 db. As the loudest part of the music is now 50 percent loader then the original source, you are forced to turn down the volume by 50 percent which has the neat effect of reducing noise by 100 percent (not zero) as the quite passages were already made 50 quieter.

They work very well. They did not really get rid of the noise but rather lowered it by a large amount. The effect on the playback of vinyl records was amazing. Quite passages were drop dead quite & load passages were window rattling. It was the best thing out there for the home audiophile before CD's came along. Even some CD's that were made from analog tapes still benefit from a 4bx unit. Any tape, FM, or TV sound is also improved with the greater dynamic range. Tape hiss almost disappeared form all my recorded tapes.

You should be able to find a used unit for very little money as they are no longer in favor as the CD is pretty quite & mostly does not need any additional help in dynamic range.

xen-uno · « **Reply #15 on:** April 15, 2004, 05:25:39 pm »

That's it!...yeah. Without NR...too much hiss. With NR on both sides...treble seemed to be muted too much. Have to admit I turned it off less on a very nice 3 head Denon which was a killer deck in all respects. A Marantz 3 head I had (well...still do...not functioning well anymore) was a 2 speeder. In the high speed mode you could fit about 20 mins of music on a 90 min cass per side. I think it was more of a marketing gimmick...didn't notice any real difference in quality between the two modes.

10^-27

Alex B · « **Reply #16 on:** April 15, 2004, 06:32:32 pm »

Once upon a time I had my Akai deck calibrated for TDK SA and the sound quality was excellent with Dolby-C on (both ways). Actually the biggest difference was in the bass quality, god old vinyl was better.

It's a sad fact that it was temporally. If I listen to my old cassettes now I have to switch Dolby off and adjust treble near to max and suffer from awful hiss.

I might record some rare ones to PC and try what Sound Laundry can do.

DocLotus · « **Reply #17 on:** April 15, 2004, 07:30:19 pm »

Boy; does this thread bring back memories

Back in the early 70's to early 80's I used to buy special dBx encoded vinyl records. They were awesome; S/N ratio of 90 db or greater, tremendous bass, very clean highs, no pops, clicks, or rumble of any kind. As they were compressed 50 percent with dBx encoding, the groves were very close tighter & only one half of the vinyl was used so very long playing records could be made which was great for classical of long jazz pieces. They could get up to 50 minutes playing per side.

You did need a dBx decoder to play them otherwise they sounded awful as they were so compressed with the dBx encoding. You could use the decoding half of a dBx encoder/decoder to play any dBx source material.

The was also a company called Barclay-Crocker that made custom 7 1/2 inch open-reel prerecorded tapes for many years. All of their tapes were recorded 1 to 1 on professional machines & with Dolby B (10 db noise reduction - this was before Dolby C). They were very clean (for the time).

When Dolby C (20db noise reduction) came along the CD was also introduced at about the same time. Barclay-Crocker made the decision to skip Dolby C in favor of dBx as it had 50 percent cleaner sound then Dolby C (40db vs. 20db) & made the custom tapes sound as good as CD's.

I bought a lot of the dBx encoded tapes from them just before they went out of business. Yes, the CD killed them.

I also recall the fight over which noise reduction method was going to be used for the then new TV stereo sound transmissions. Fortunately for all of us, dBx won out as it was simply the best available. So, today all non-digital TV stereo sound is sent out dBx encoded & the TV set decodes it. As all TV's have a dBx decoder in them, I assume that even digital TV sound is dBx encoded before it is digitized & transmitted. I'm not sure about how Dolby 5.1 surround sound is handled but it too may be dBx encoded then decoded at the TV set before going through the Dolby decoding circuitry.

One thing is certain... we have come a long way in the last 30 years. Things that we could only dream about then are common place today.

Isn't technology wonderful.

cascius · « **Reply #18 on:** April 15, 2004, 07:45:08 pm »

Quote

One thing is certain... we have come a long way in the last 30 years. Things that we could only dream about then are common place today.

Isn't technology wonderful.

Yeah, seriously! I never could have imagined that we would have portable players smaller than a walkman capable of having up to 10k songs. It's insane!

-Cascius

paulr · « **Reply #19 on:** April 15, 2004, 07:48:43 pm »

Wow DocLotus! You should encode some of those tapes at 96kHz! I'd love to get my hands on some old, and excellent analog recordings.

I have a fair sized audiophile LP collection, but my turntable is a goner.. I need to get a new one. That laser record player sure looks nice *cough* $10,000 *cough*.

xen-uno · « **Reply #20 on:** April 15, 2004, 08:08:00 pm »

Technology stinks!

1) It's made me want to live alot longer (to see what's next) than I possibly can

2) I no longer want to waste money on clothes/houses/cars and other low tech items

3) It's made me reclusive and anti-social...all I want to do nowadays is sit in front of a computer and do creative stuff

4) Have become very impatient with things (such as real life) that move at less than computer speeds

5) Finally (and most importantly)...right arm has become weak since I no longer do repetitive 1 gram lifts moving the turntable arm from the mooring point to the record

10^-27

DocLotus · « **Reply #21 on:** April 15, 2004, 08:14:22 pm »

In the 70's, I had a B&O linear tracking record player $1.000 & a $600 B&O cartridge. Coupled with the dBx records, a great dBx decoder, a 4bx dBx expander, and all McIntosh electronics with 4 speakers it did sound really good. For $26,000 it should.

Now I have everything on my computer. Does not sound as good but is much more versatile as I can do almost anything with it from checking my e-mail to watch DirecTV.

My next step is a wide-screen (hopefully a 30 incher) desktop monitor; this should become a reality in the next year or two.

DocLotus · « **Reply #22 on:** April 15, 2004, 08:16:24 pm »

"Technology stinks!"

Funny

JimH · « **Reply #23 on:** April 15, 2004, 08:56:42 pm »

Quote from: xen-uno on April 15, 2004, 08:08:00 pm

2) I no longer want to waste money on clothes/houses/cars and other low tech items

Funny, but you left out women and they sometimes aren't very forgiving.

DocLotus · « **Reply #24 on:** April 15, 2004, 09:00:24 pm »

They are also VERY $$expensive$$

INTERACT FORUM

Author Topic: Dolby NR (Read 7528 times)