Could this be one reason tubes (and perhaps records) sound better?

This is not a new finding, rather it keeps cropping up in the hearing literature...
"White noise improves hearing":
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I'm not sure tubes sound better - it is just a preference.  Noise is often used in imaging to improve resolution, but in sound it is likely to improve dynamics.  Distorted guitar sounds more dynamic than clean Jazz guitar at the same level.  Added noise is a form of distortion.
It might be that in striving to create noise-free systems, solid-state and digital audio went below subjectively optimal levels. That suggests experimenting with adding slight amounts of white noise to virtually noise-free solid-state systems to see how that affects aesthetic evaluations. This could be done using a continuously adjustable noise source to dial-in a most-pleasing level, which will of course vary with the listener as well as the source and other features of the system. 
Not only is this not a new finding in hearing research, its also not a new finding at all, in fact it has long been known that human perception is improved by the addition of noise.

Do a search for dither. Dither is noise added to a video signal that results in greater perceived resolution and clarity. Dither is standard practice in video mastering. Been that way a very long time.

More recently, and even less well known, Ted Denney III introduced Synergistic Research ECT, HFT, and PHT, a whole range of transducers that operate on the principle of dither or added noise. The noise introduced by these tiny little things is inaudible, yet somehow improves clarity, depth, extension and detail to an amazing extent.

The fact (and with this much research over this long a time frame, its a fact) that white noise improves perception is however nothing to do with tubes and records sounding better than transistors. Its nowhere near as simple as that. Rather what this does instead is shed light on the complex nature of what we so blithely dismiss as "noise".

I’ll give an example to illustrate my point. One night back when I was still playing CDs about as often as records we got to the end of one side when my wife said she was amazed how quiet it was. The record. Which I thought she meant, because it was one of my more silent ones. But she said no, she meant its quiet compared to the CD. Which certainly cannot be the case, for sure not by the normal meaning of noise being hiss and ticks and pops and all the other obvious noises. These are NOT what she meant!

I’m constantly fascinated with the reactions of normal, as in non-audiophile, folks, people who really just want to enjoy a really good musical experience. So I ask questions, and always carefully worded questions, very carefully worded so as to influence their answers as little as possible.

As long as that takes to explain its shorter than the exact questions and answers, which nobody can remember verbatim years later anyway. The gist of it is that she perceives the records as having less noise because to her the noise she hears when playing a CD is not hiss, the noise is the entire signal. CD, digital, solid state- these things measure great but sound bad because the whole damn signal they put out is noise! Or to put it slightly more politically correct yet technically accurate, the noise is so inextricably woven into the signal as to make it near impossible to differentiate it out. The signal is the noise!

Now, they are not all the same, these SS and digital devices. Some are better. Those we compliment by saying they are analog-like. Close to analog. This is after all the highest compliment you can pay a digital component. The highest compliment you can pay a solid state amp is it sounds tubey. Even better if it has tubey magic.

Nobody ever in the history of audio referred to transistor magic. I just did a search for "CD magic" came up with some magic tricks. Search "tubey magic" pages of hits, all in reference to the sound. Precisely nobody ever said solid state is magic. Measures well. That’s about it.

Last thing, the white noise thing, strikes me as a very close analog to bias. Tubes, tape deck heads, lots of stuff use bias current. Bias is used in all kinds of cases where the initial response from zero is poor, but the response from an elevated state is much better. So a very small bias current helps keep the part in an excited and more responsive state. Seems pretty obvious to me that is part of what is going on here. But then if you’ve read this far it should be obvious that what is obvious to me is actually kinda hard for most to get their minds around.

I’m telling ya, they just aren’t paying me anywhere near enough for this quality writing.
@millercarbon  I believe that we got used to particular system sound, different from reality.  We know that in concert the sound is different but at home we like what we hear.  When I replaced CDP with Benchmark DAC I had impression that sound is strange.  It sounded too clean - like something was missing.  One person stated that he can hear all instruments separately, but prefer to hear them as one (sound blob).  We need to learn to listen.
I don't know much
But I know I love you
And that may be
All I need to know

.....   Linda Ronstadt, Aaron Neville

It seems like the problem facing audiophiles is that we feel like we know it but at the same we don't really know it.  Everybody has their own theory of "why", but can't seem to put a firm finger on it.  Like some unexplained instincts or something subconscious that is fooling us at the same time confirming us.  

How do we resolve such conflicts?  On the one hand, hearing can really be complicated (otherwise we would know it by now), on the other hand, with the current advance in technology, it's a bit unreasonable to ask for more.  All the equipment that can measure down to sub pico second so not sure if more sophisticated equipment will do any better.

Anyway, it's lunch time...

Yes, this topic has come up on a regular basis. I believe it is due to generational overlap, in that, those of us old enough to remember when everything was powered by tubes and turntables were the only means of listening, now overlap with succeeding generations of those who've been raised without.

One generation is enough to establish a trend, tastes, and preferences. Imagine several added into the mix. Nostalgia can be a potent potion and passed down through generations as well. Add in the need to rationalize a particular preference and everything comes full circle.

It all boils down to preference since it's all, at best, imaginary.

All the best,

Before science, people when looked up the night sky at the milky way and thought that the milky way was sort of like a backbone, a backbone of the night sky, and if without it, the night sky would fall down on earth and could end all life. Now we know better but probably still not enough. Quantum physics is all but a stop gap measure until something better comes along. Things we though we knew too well in the past, now turned out to be false or at least only half true.

"I think therefore I am". Indeed, trying to see "reality" has been man’s quest since the begin of time. But the more we know about "reality", the more elusive it has become, and now there are people who are even doubting that we will ever be able to know the actual "reality". Even the question itself is absurd as if asking what is "infinity" as if there is such a thing other than it is just an abstract human concept.

So why is tubes are more "musical" than solid state? Hm ... I am afraid it will be "I hear therefore I am". Maybe someone will devise a test to figure out what that is. I think I’d give up waiting for it before giving up trying to find God (or Goddess if you're horny like me :-))

Well, it ain't no use to sit and wonder why, babe 
Ifin' you don't know by now 
An' it ain't no use to sit and wonder why, babe 
It'll never do some how… 

Thank you for your wisdom Mr Dylan
We need to come up with agreed to standards, benchmarks, yardsticks. 
Not measurements only, but points of reference that we can agree on. 
Then we can explore together and come back with real improvements. 
We need to come up with agreed to standards, benchmarks, yardsticks.
Not measurements only, but points of reference that we can agree on.
Then we can explore together and come back with real improvements.

Don't stop believin'
Hold on to that feeling
Streetlights, people
let me add some gas to the "fire-ery" discussion. If it possible that the albums from the 40's, 50's and early 60's had white noise built into their recordings? At this time sold state was not "state of the art" in recording studios...might it not explain why all my firends keep asking me why the original recording from Frank S and Tony B and Miles, etc. seem to just sound better?  Apologies in advance, I am not a audiophile expert, really enjoy the hobby and just trying to learn. Thank you
Thank you millercarbon for pointing me to the literature on dithering and your patient explanation! It would seem the whole added-noise topic has implications for all the tweaks audiophiles pursue to eliminate or modify the noise in the system (including that coming in from the music-signal source).
Re brettmcee on standards, I should expect no single ideal could be found, not only due to variations in source type and taste, but due to the huge variation in hearing (e.g., our frequency-response profile changes dramatically with age). So custom equalization of the noise level might be a new holy grail for system optimization - with the curve heavily source-dependent and changing over one's years. At best we might hope for reliable user-friendly equipment to do that kind of detailed full-band customization.
Sorry, forgot to add, my system is Cary Audio SLI-80 Signature integrated, Chinook Pre-amp, Linn Sonedek LP12, audio Mirror Tubadour III Nos Tube DAC and Fritz Carbon 7 speakers. 
So what would happen if you buy a stand alone white noise generator and have it playing at low levels in the background while you listen to your system?

Seems like most of them are under $50. Maybe $200 for a deluxe version. By audiophile standards this is the cheapest tweak you can imagine
Hiss and pops and clicks and other forms of tube and record noise are not white noise.
If the signal path is absolutely clean then there would not be any need for the added white noise.  But alas ... our digital gears are full of "correlated high frequency" noise.  Some DAC intentionally have "white noise" added to mask or lessen the effect of "correlated digital noise".  
Hiss and pops and clicks and other forms of tube and record noise are not white noise
It can get complicated. To make a general statement can lead to over-simplification.  Are those "hiss", "pops", and "clicks" occurring randomly?  That's something to think about.

Vacuum tubes ,is just another way to tune your audio system , your whole system is about synergy .
cables , power cords, type of digital design , as well as turntable, 
type of cartridge types all are parts of tuning your system to your sonic preferences .
@millercarbon I am disheartened by your continual hawking of the extremely questionable products of Ted Denny and his Synergistic Research company.  None of the products you mention address white noise, dither or anything else appropriate to this discourse.

The ECT, according to their advertising: " When ECTs are placed on or in an electronic device UEF nano-particles within the ECTs are excited by the components EM fields".  Nano-particles indeed! 

Again, according to their ads, the " HFTs oscillate at high frequencies in response to acoustic pressure in your listening room to compensate for acoustic distortion and correct for phase anomalies by re-cuing your rooms acoustic response to sound pressure." 

Finally, no explanation is given for the PHT, just that it will bring about a " lower noise floor, increased resolution, and improved bass extension with increased air and soundstaging".  This is the same verbiage used by everyone who has ever sold scam products to audiophiles. 

Keep in mind that outfitting a audio system with the requisite quantity of this garbage will be paying multiple thousands of dollars!

Anyone with a modicum of common sense would see through this as the unabashed pseudo-scientific snake oil it is, and you are doing a disservice to the good people of Audiogon by recommending this stuff as anything more than that.
Before jumping to conclusions about this being the same as dithering or any other conclusions, it would be good to read the whole research paper, and not just the headlines.

This is a new finding, especially the research into the cause of what is happening.

Dithering is a technique to add random noise so that things don’t "stick" to a given value, typically in a digitized system, but not exclusively. Let’s say you are trying to digitize a value, and that value if you have the resolution was 12.7, but since you don’t, you get 12 (or 13) and it never changes. Adding dithering will make that 12.7 bounce between 12 and 13 (or higher) such that the average = 12.7.

In the paper (research done on mice), what they found is that the white noise (fairly high levels) suppressed neural activity. That would be the opposite of adding "bias" .. more like an automatic gain control turning down the gain. The white noise reduced the firing rate of the neurons associated with the frequencies, but increased the accuracy. The white noise was within 10db of the signal. Suppression of neurons would not be akin to dithering either.

Noise would typically impair frequency discrimination and impairs most auditory tasks. What this study showed was that noise could improve frequency discrimination when the frequencies are close to each other. It showed no improvement when they are farther apart.

This research paper would be more inline with what you suggest in your OP, w.r.t. low level noise increasing perception: , though they did not dig as deep into the underlying neural responses. While in the paper posted above, the neural responses were repressed, in this paper, they were increased. I could see that be indicative of dithering since neurons can be threshold triggered, more indicative of digital response than analog.

... and jnorris2005, +1 !!

@millercarbon Thanks VERY interesting
I think we've reached another low when we have to rely on mice for our audio gears :-)

Also we have to outlaw "copy and paste" :-)
Probably should move this comment to another thread but not sure where. I had the same experience as kijanki states above. Relative newbie, I just bought my first external DAC, an old Berkeley Alpha DAC Series 1. My immediate impression wasn't what I heard but what I didn't hear. I was playing chamber music and I distinctly detected the silence spatially between the seated musicians. Don't know how or why, but I definitely noticed it.
My belated thanks to jnorris2005 and atdavid for their critical comments warning of sales pitches (I suspected that one) and educating me about dithering vs pure white noise. Perhaps someone has built or will build the kind of variable source that would enable systematic study of white-noise effects on music perceptions.
Until then I'll just have to continue experimenting with the electronic volume equalizer in my processor (Yamaha CX-A5000 with ESS 9016 DAC), which to probably no one's surprise still makes stereo (as opposed to multichannel) sources sound best in direct/bypass mode (direct mains are Magnaplanar 3.4s driven by a Denon POA-2400A - truly antique stereo set but still sounds superb).
There are white noise generators readily available with volume control, they are used as sleep/work aids. If you have an analog mixer, you could also mix white-noise from a laptop to whatever else you were listening to.
Personally I would not recommend intentionally generate white noise in your listening environment.  There is a difference between what happens in the laboratory environment and your own.  Just because they said so, does not mean it's true.
... which is why experiments are recreated, for validity. I am struggling to see any merit in your advice to someone who wants to experiment.
Lose the vinyl and the CDs and listen to reel to reel tape. It’s all you need.
... which is why experiments are recreated, for validity. I am struggling to see any merit in your advice to someone who wants to experiment.
Go ahead Mr. 24/7 lols.

The Nelson Pass article where he describes his little harmonics generator goes a long way to providing a clue to the clue deprived. I'm glad Nelson is around as sort of an "anti Ted." Also, well said jnorris2005, as I utterly agree.
I think most designers already knows this but has to find a combination from a lot of parameters. For example the designer of many Parasound amps has said that he worked hard to avoid the 7th harmonics since that don't sound good at all but many circuits produce them. Others may focus on other things.

Some like to use negative feedback in amps to make them measure better and others thinks that destroys the sound. The latest Dartzeel amp has configurable negative feedback. If you hover your mouse on their web site title you can see the phrase "In the name of music: listen first, measure later".
1+++ atdavid and jnorris2005. Now for a little anthropologic physiology.
There is always noise in our natural environment. Those of us that could identify danger through the noise out-survived those that could not and so our hearing has developed certain sensitivities. We are very sencitive to phase and volume for location and we have a canny  ability to evaluate and identify important sounds through noise. The difference between a twig snapping and the rustle of wind through leaves. Higher levels of background noise require us to pay even more attention to identify danger. Background noise causes us to focus on important noise like music. We do this without thinking about it. We listen better with background noise. Some of us actually feel uncomfortable without some background noise. After listening to Tape hiss and vinyl noise for all these years digital sounds unnatural because there is no noise and I do believe many of us prefer vinyl because of the background noise but still find the occasional loud pop disturbing. It makes you snap to attention reflexively. Call it dither or bias or whatever. Noise is definitely an important part of the equation. This would be a great subject for further study if it has not been already. 
One night back when I was still playing CDs about as often as records we got to the end of one side when my wife said she was amazed how quiet it was. The record
I like the fact that every day. Is a learning day. When my girlfriend said lp was quiet and clearer I thought she meant it because her youth had crackle and scratch versions and mine was a new 180g pressing.... I'll have to carry out an experiment with her 
Background noise causes us to focus on important noise like music.
I listen better with my wood stove hissing warmth and also with a malt in hand. First point relevant, second not so.... 
If you suffer from tinnitus (I do), it becomes difficult to not hear your interior, artificially high noise floor. I'm one of the lucky ones who doesn't hear distinct notes, transients, or percussive sounds.

White noise is one of several perceptual tools that "mask" white noise. The mechanism-of-action is basically misdirection...flooding the brain with non-specific aural cues makes it harder to focus on one's tinnitus. White noise is effective: I use it for sleep and wouldn't want to do without it. 

And thanks to a pretty bad case of chronic migraine, I have several rescue medications that also mask tinnitus to a degree, albeit by very different means than white noise.

For what it's worth, I use either pink noise or gaussian noise mp3's to burn in gear. Gaussian noise is the best sounding/least artificial of the noise variants I've heard.

And yes, echoing several above posts, there's a history of using noise of various kinds in audio gear.
desktopguy, sounds like you are handling your tinnitus very well. I have had two patients that were crippled by it. Interestingly, both developed Alzheimer's. So, as long as you can handle it you're in business:) The technique of masking not only works for tinnitus but other sensations the most important one being pain. Any child will tell you the cut feels better after you put a Band-Aid on it. When I give an injection I give a firm pinch which covers up the needle stick. The pinch and the Band-Aid are masking sensations. 
Desktopguy, just in case you did not know 3 new meds where just approved for migraines. Erenumab (Aimovig) is the one I am familiar with.
It is a once a month subcutaneous injection that decreases the frequency, intensity and duration of migraines. I have not had a chance to use it yet.
You might want to take it up with your MD. 
In fact my high school Calculus teacher (easily the smartest high school teacher I’ve ever seen) in the early 1990s referenced a study with the same findings: adding a small amount of static noise improves human detection of low-level signals. The topic came up seemingly quite randomly, in one class. But I remember it quite clearly, and certainly thought of it when I got into vinyl in the 2000s!

Human perception is complex. With tubes the idea is that low order distortion is sonically pleasing, and that higher levels of it can mask lower levels of high-order distortion which is very objectionable to human perception. So run tubes and vinyl; stop fighting your nature :)