What is Dolby Noise Reduction? Dolby's Humble Beginning 

Even as a musician/engineer, this is the most lucid and straightforward description of 'Dolby B'. More power to your channel !

The companding in Dolby noise reduction is more complex than just setting an equalizer. The companding is accomplished by varying the volume of the desired bands *_depending on how loud they are!_* That means it _changes over time._ The Dolby playback circuitry has to sense when to change the volume to match the amount of change during the making of the tape. That's the real reason for the Dolby sign on the level meter, record levels need to be set to match the preset playback settings. A mismatch can sound like there is a pumping or breathing effect to the sound.

It's amazing how much this channel has improved over the course of a few years. The content has always been excellent, but the filming, delivery, and production quality have really come a long way since this video was uploaded. Thanks!

The remarkable ease with which you explain these sometimes difficult to understand subjects never ceases to amaze me. Definitely appreciate your work!

This video is SO GOOD! Having your voice being fed through the actual mechanisms is so informative. Showing the actual effect of the EQ in "real time" illustrates everything in such a clear way. And then the alliteration? GOLD, JERRY! GOLD!

...and that over-emphasis on the treble sound is what I loved back around 1982 when I was recording my first band. I'd record using Dolby, then mix the final, from a TWO TRACK cassette deck, WITHOUT Dolby so that it was crisp and bright.

Back when Dolby was popular, I was just starting my interest in audio electronics. I made many recordings with cassettes on my Dads Technics tape deck (it was a mid 70's model that did type I and II tapes, and only Dolby B). Like many here in the comments section, I prefered to keep Dolby off. However, now that I'm in my 30's, and have been able to get back into high end audio equipment, I find that I prefer the Dolby when it comes to pre recorded tapes at least. An example; I recently bought a NOS Bon Jovi - New Jersey cassette (1988 album). It was recorded on what appears to be Metal (type IV) tape. It has Dolby HX Pro (a system that should work perfect with my Bang & Olufsen Beocenter 9000's cassette deck), but no Dolby NR. I compare that tape to my mid 90's cassette of Weird Al's "Even Worse" album that is type I tape WITH Dolby B NR, and to me, the Weirs Al tape wins in that sound test. Sad really. I think Dolby B was a great thing, but cheap consumer decks didn't have it, and that was the eventual fall of it, and all music formats really. It's my theory that record companies want to push the album out to as many consumers as possible, and since the vast majority have cheap systems, with sub par amps, speakers, ect. The majority of the media is meant to play best on those systems. It really sucks for people like me who really enjoys music, and has put a lot of time and effort into my music listening set ups. /rant

Noise reduction is still used today, though not to reduce noise from the recording media itself. "Intelligent" systems is used to remove any unwanted noise from the source: Wind noise from outdoor recordings, hum from guitar amplifiers, pops from singers blowing too much into the microphone, hiss from electronic instruments, etc. I record electronic music in multitrack and even though I don't notice the noise from a keyboard on a single track it will certainly become noticeable if I record 16 tracks each with a thin layer of noise that is added up 16-fold.

Dolby A came out just as multitrack recording was really taking off. Many of the best recordings of the late 60's onward would have been impossible without it. Take 1968's triple-Grammy winning Switched-On Bach. Recorded on an 8 channel recorder back when synthesizer keyboards could not play chords, this meant recording each line of music to a single track, mixing the filled tracks down to free them up then doing it all over again. Without Dolby A's noise reduction this track bouncing would have increased the background noise until the tape was unuseable. Instead it won the 1970 Grammy for Best Engineered Album.

Idk why but.. 5:49 looking at this cassette tape is really nostalgic to me, very satisfying. My parents couldn't afford a camcorder but discovering audio cassette recording was a big part of my childhood. Where the audio recording took place like parties in such, I remember the exact situation in mind and playing the audio in reality it was like a video camera to me (with imagination). Nobody understood the kid with a boombox but that was the only entertainment I fully enjoyed. Didn't mean to throw a story but I simply enjoy your content vid by vid, very glad to be a subscriber.

Love the layman's term breakdown, good presence. Been watching a few of your vids all day. you got a sub here

Your channel is AMAZING! I love the detail you go into for seemingly tiny and random things!

@Technology Connections I had a cassette deck that had the option to study how the noise was compounded by "listening" at the noise for about 10-20 seconds of the tape. The idea was that each tape was quite homogen regarding the magnetic layer so the deck adjusted itself to best settings to remove hiss. It also was "smart" enough to refuse engaging this system when a low quality cassette was inserted.

This was good to know. I never questioned why sometimes when turning on Dolby sometimes made stuff sound better and others just got quite.

When I owned reel to reel the key on those would be faster tape speed. So that worked but at a sacrifice for time, and it still did not eliminate tape hiss, but since it offered a better dynamic range, which helped. Sadly most commercially bought tapes ran at 3 and 3/4 IPS which is below the 7 and 1/2 ips. Early recordings in studios suffered from that, when boosted up to higher levels, still revealing major tape hiss. Then in the late 70s and early 80s we got Dolby. First for movies, as the stripe audio on movies, also suffered the same hiss and crackle noises as tape. So to improve that, Movies got noise reduction, which for movie theatres meant a huge improvement in sound. In fact, my very first cassette deck was a TEAC with DBX capability. While it was non-standard, it did offer nearly CD quality sound. But I soon learned that to get good sound you did need Chrome or Metal quality tape, to get a good experience. And if you play back a DBX tape on a normal tape deck, it sounds like it was recorded on a cheap tape recorder, and lacking quality. DBX took the process in the other direction. You recorded at LOW Fidelity, and then Expanded both the low and high spectrum, during playback to bring it back to normal, but eliminating almost all of the hiss and noise even when played back at higher volume. Great for taking a high-quality source, for your own personal collection. But there was virtually NO commercial DBX encoded cassettes on the market.

As always, a fantastically delivered explanation of pivotal technologies used in the last few decades, with that humor ("sadistic sad sack") that makes it a joy to watch! I think could be a bit shorter. I also saw in the level meter the difference in audio signal output. BTW, what is that mystery text that pops up @ 42 seconds? My challenges (not hard): What is common technology to LP, VD, and LD? ....besides the disk part. :D and how do video qualities compare between the various formats used in the 80's and 90's (beyond VHS and BetaMax) email me for answers and discus. Cheers!

"It was recorded in Doubly" ~ Spinal Tap

You are my favorite nerd on RU-vid! Sincerely, A Fellow Nerd.

They should play your videos in certain schools and pay you for the right to. You are an excellent teacher. Thank you for your hard work.

Boy, now I feel OLD! I used cassettes before Dolby......

With your explanation of Dolby NR, it sounds much like what RIAA equalization on vinyl recording does in compensation for the increased/improved sensitivity of mag-cart needle setups on turntables.

wait… thats a Pebble! You already deserve mad respect, but thats the icing on the cake.

Very interesting, thank you. I had a ton of cassettes back in the day and always thought the Dolby button was kind of magic. I never really understood how it worked. I'm surprised it was that simple.

Okay and now a video on the Dolby HX-PRO noise reduction... Really great invention. Only needed when recording and fully backwards compatible.

There is a serious lack of a proper 21st century audiophile tapedeck, for digital archiving, that can playback all the different tape types (proper bias adjustments), let alone Dolby Noise Reduction, so that people can simply enjoy (and preserve) their old cassette tape collections. Play tape one more time, and then have it saved on a thumb drive, on a hard drive, in your iTunes, or saved in a cloud account.

In theory, you could hook up an equaliser between your source and the cassette deck. Then while recording, you could boost the high frequencies while keeping the mids and lows flat. Then during playback, you could reduce the high frequencies back to the flat position again, assuming that you play back your cassette through the same equaliser. Or you could just reduce the treble on the amplifier, and your recording should still sound bright. This would also eliminate incompatibilities between different cassette decks, where noise reduction systems are concerned, as was often an issue, even with two different decks with seemingly the same noise reduction systems. On the recording deck, the cassette would sound fine. But on a different deck, with Dolby B for example, it may sound slightly muffled, or compressed.

The tape on the non-dolby unit brought back so many memories holy shit. Wow, the nostalgia is real

Dolby Labs first commercial product was Dolby A. This was a professional noise reduction system. B came some years later.

I have a cassette player without any external option for calibration. It can only switch dolby on or off. With Dolby engaged, the recording is muffled and has an "artificial" quality to it, because a frequency band gets manipulated separately. Also dropouts in the tape get emphasized, because the decoder expands more during those. The constant bright hiss doesn't feel like a problem to me, and the recording seems to have wider spectrum with more air, even if some of it is actually noise. I tend to prefer aliasing over brickwall frequency response too, even if the latter is mathematically accurate. I get an impression that Dolby B is an unreliable system. It is not possible to tell if the machine on which the tape was recorded was in good alignment.

I always wondered just what that button did. Thanks!

This is quality content. You make terrific deep dives into recording media.

Like the phono RIAA companding.

This is the coolest channel!!!

Thank u I just love the way you teach. I've always noticed this with my decks basically lm Trading hiss for warbly sound when using Dolby.

When we moved into the digital age, the problem that still exists today is that of volume leveling. A digital recording is so dynamic suffers that the digital track is over or under a good volume level. It's quite noticeable where DSP and resampling occurs, or when originally analog is boosted or reduced. DSP in the 1980s is what changed all of that. So today we suffer with constantly having to alter the volume levels of most media to make it play at a normal level.

I pressed "like" at 3:30 ;)

Great explanation! Congratulations!

I am sure you will have millions of subscribers soon! Good job!

You get a like because you explain this stuff!

5:50 Creepy music. O_o Very weird. 6:19 Even _more_ creepy! 😨

I always had issues with muffled sound playing pre recorded Dolby encoded tapes with Dolby NR on for some reason. That`s why I always just left it off. But when I recorded tapes I would have it switched on. Go fig. For some reason they sounded better even with NR switched off. This wasn`t just from one deck. It was several that did the same thing.

Yo, Nice tie. You should make more of these videos.

But Dolby noise reduction improved optical sound, so you could get the sound quality of magnetic sound tracks with easy duplication and always compatible to the optical sound standard from the early 1930's. They also implemented the developments for matrix based quadro, to encode 4 channels in 2 tracks. So it was like the 4 channel sound known from Cinemascope.

Efficient, logical, effective, and practical: using our abilities to the best of our abilities. I’ll assume that was intentional!

I was born on 1989 and I use dolby B to this day recording my cassettes :D When you don't have enpugh space on your SSD for all the vinyl records :D

I'm sure you know this, but pre-emphasis is part of the red book CD audio standard, so it has been used in the digital domain as well. As I understand it, it was due to the frequency response of early ADCs being bad in the higher frequencies, and noisy low-pass filtering to get rid of frequencies above 22050Hz for the digitization.

I want to hug him, he looks fun to cuddle

Noise can be a problem. The 96dB nominal SNR for CDs is only true for full peak-to-peak amplitude recordings. Reduce the amplitude (volume) of the recording and the noise increases. The SNR is further reduced by the deliberate addition of "dithering" noise to reduce unwanted audible artefacts that digital systems introduce when recording low signal levels.

5:51 That RU-vid library music sounds "weird" all on its own...

Damn it is nice to see a Pebble OG in the wild. Totally love mine

dbx was the best of the best when it came to tape noise reduction, but it never really caught on except with audiophiles. A good dbx deck sounded so good I couldn't tell the difference between a taped copy and the source cd. Dolby kills the high end, and various other problems.

I wonder if they apply these principles to radio telescopes, or even digital visual telescopes, hmm, maybe even digital cameras. Great video, very fascinating.

If I only knew this in 1991! You sir, are a god among men.

If you are looking for new video ideas, this might be kind of cool: I know you have done videos on vacuum tubes already, but it would be maybe interesting to do an in depth look at guitar amps that used tube to create a "distorted" effect. Among musicians, the understanding seems to be that you "overdrive" the tube by putting a really hot signal into it. But, based on what I've learned I've learned from your videos, that shouldn't really create a distortion effect, because the input signal only controlled the control grid, which simply turned the amplified circuit on or off. So, where does this idea of "driving" or "saturating" the tube come from? Is it really just that if the signal feeding the control grid is too hot you start to distort the sound?

Yes - it was brilliantly elegant! Have you done one yet on DBX? They are very different indeed.

My cassette deck (Technics M233X) has Dolby B and Dolby C as well as DBX.

Very informative. Nice bow tie. Cheers.

I managed to make my tapes sound louder and cleaner than CD'S by observing this technique and using the correct top of the line deck that doesn't hiss at all.

I liked how watching the Dolby C part had satirical CC like "that's so weird" lolz

bro, this stuff seems like it shouldnt be interesting but its fascinating! edit: 6:25 is so unnerving

Lol, I love the "their first product" easter egg!

Good Video - Can you show an example of undecoded DBX Noise Reduction?

Ahh.. That Good old Akai GXC709d

I remember having a seperate Dolby component for my cassette deck in the 70's.

I love this noise

Early CD's had a similar pre-emphasis as well. Unfortunately this was one of the things that contributed to the perception of digital sound as overly harsh, when played back on a non-compatible CD player. Very few modern players are compatible so ripping an older CD can present some problems. And I think it may have lead to some confusion among mixing professionals as it seems some continued to employ pre-empasis in mastering without realizing that it was no longer supported.

Those alliteration’s though (also that music sounded surprisingly similar to bejeweled’s Soundtrack)

I subbed to your channel really interesting and very informative only discovered it today but it's bloody good learning quite a bit now that I never knew thanks

I'm not sure where you got your info but I think you're wrong, my understanding of the way Dolby works is based on the principle that two signals that are 180 degrees out of phase cancel each other out. since tape hiss is normally random you instead record a known level of designed hiss, upon playback you mix the signal with the designed hiss but 180 degrees out of phase of the playback and the 2 cancel each other out, most importantly with out effecting the original sound. this also makes tape head alignment critical, any miss-alignment will affect the performance of the Dolby system. for many its an easy thing to experiment on at home if you have something with stereo speakers that are manually wired. they are marked positive and ground so that you keep the speakers in phase. reverse 1 speaker and listen to what it does to the sound, the effect will vary depending on the distance the speakers are apart and would be most pronounced if you play a test tone. while next to a speaker you will hear the tone as usual, but as you move to the center between the speakers you will notice a drop out in amplitude. it wont drop out entirely due to reflections of sound waves and such. While this method was originally for noise cancellation it was eventually used to encode multi-channel surround, for instance sounds that are perfectly in phase if you take the right channel and inverted it 180, then mix with the left, they would cancel each other and the remainder would be the rear. various methods are used to separate the center channel, and retain the Left and right. but the concept is the same. I'm pretty sure they use the same concept for noise canceling headphones, that's the purpose of the microphones on them, they are sampling the sound around you and then inverting it and as the 2 sounds reach your ear they cancel. this works with repetitive sounds best like the drone of an aircraft engines, other than sounds that are constantly varying in level and frequency.

I’m strange...I actually like the sound of tape hiss. There’s a sort of nostalgic enjoyment of it going back to my younger days in the 80s.

excellent videos thank you

You are awesome! This is awesome

Please do a video on how Dolby atmos works.

This fantastic!

Wonderful tutorial! So coming up to 2020, how does "Audacity" remove noise? How come you are not a college professor?

Cool bow tie!

Got to confess I artificially added that tape sound to a few bands when I was mixing them. Bit of an artistic license. Only when it sounds right

1:22 This may sound weird (heh, sound), but that noise is actually quite comforting to my ears.

good explanation keep it up sir. And can you recommend hi fi cassette deck to play all type of cassette?

When I was a kid, I assumed the Dolby system was invented by Thomas Dolby, because as we all know when we're children, two things having the same name cannot be a coincidence. :)

thanks

I kinda like the hiss honestly

I know this video is older but anyone happen to know what a Dolby FM Broadcast Unit Model 334 with the Type-B Cat No. 66 card in it would run these days? It's all but impossible to find them and information is minimal with the exception of the original documentation.

Most of my Cassette tapes are not recorded with DOLBY, and I do not have Hiss in my recordings. First of all your SOURCE is the most important part. If the source is a very good recording, and has no hiss in it, you do not have to use Dolby; Because Dolby ABSORBS the clarity of the recorded sound on your tape. Most of the recordings these days are Digital and they do not have background Hiss; so you do not need Dolby; it will be helpful if you already know the song or the music very well so that you can control to bring down the high peaks. Also it is very important to have a High Output Cassette Tape. Finally, if you make a good full recording, you don't need Dolby. If you notice that there is a little bit of a Hiss in your recording, bring down the TREBLE of your Amp. to 1:00 or to 2:00 PM then you don't have any Hiss. Good Luck. Krikor from L. A. CA.

Can you explain how HDCD works? How does it decode 16 (or 14?) bits of audio into 20 (or 24?) bits of audio? And how does it provide an entirely different master? How does is it compatible with normal CD players still and provide everything on the same PCM stream as the 16 bit audio? I don't understand, but it works great when you decode it using certain music players. You can even decode in post using lossless 16 bit wav files. I can't find much information when I try to research it. Thanks!

I'm born in 2005 and i listen to cassette

Damn, that stock RU-vid music is really hip!

What I would like to know,, did early CD manufacturers record their CDs using Dolby NR-enabled recordings?? I think that they did, because they often had that awful tinny sound associated with a Dolby encoded tape on a non-Dolby machine. THAT would be a cool research project for ya... _>

i liked the way dolby c sounded on a non-c machine.

Always hated dolby, still hate dolby, but your channel is awesome. Subbed.

Your early videos are far less emotive. Still informative and excellently edited though.

this video literally explained what the dolby button on my 2001 mazda mpv's media stack did. wow.

Bring that Dolby C recording down to half speed and lay some Japanese mall sounds on it and you've got a vaporwave summer hit

Dude this stuff is GOLD! You earned a new sub after the VHS video! You present technical content in a very intelligent form without boring the viewer. You're VERY well spoken and don't ever drift off the conversation, yet still have a hint of dry humor. I love this!

You should do a video on the RIAA curve and how it solved the problems of recording high fidelity sound to records and helped establish the 33 1/3 rpm standard. Keep up the good videos!

Funny... I cannot hear that cassette noise. So then I remenber: "Ho yeah, my tinnitus!" . . Yup, this thing "sings" louder than that annoying cassette tape hiss, (that I still remember from the old times). But with regards to the tinnitus... well, like my doctor says: "Just forget about it". . . And then he adds: "But if for some reason, some day you can't forget about it anymore, then come back here, I will prescribe you some anti-anxiety pills to help you forget about it". . . So yeah, here is my piece of advice: "Stay away from tinnitus". If you can.

I rarely used the noise reduction. Sure it got rid of the fuzz but it also muffled the sound. Edit: I should watch the video before commenting hehe.. I wasn't recording properly. Nice to know the way around the muffle.

I hope to see many more videos like this one, and I wish you many thousands of subscribers.

Only 320 likes in four months? This channel must not be widely known yet. Nice vids! More people will notice them in time.

What a shame we didn't have videos like this to tell you all about Dolby when we needed it the most!