Nose floor vs audible effects

[sandyk]

The point is that at normal listening levels of 80-90 dB*, the noise floor on any 16-bit or higher DAC will be below the human threshold of hearing and will be inaudible. I hope this is clear.

And it can't possibly interact with other low level material just above the threshold of hearing , or can it ?

Miska and others have already said that it is possible to hear things below the system's noise floor.

[Jud]

Hi Jud

The Forum area DSP, Room Correction, and Multi Channel Audio was created specifically for this purpose, and is where many of the "bits are bits" and "RB CD is as good as it gets" brigade can hang out without further heated discussions as to why additional further digital processing is needed, or is even a good idea.

We really don't need any further acrimonious discussions on this subject in General Forum. That's why that area was created originally.

 

Regards

Alex

 

I'm fully capable of participating in a non-acrimonious discussion of the topic in the general or DSP forum, so no problem either way.

[sandyk]

I'm fully capable of participating in a non-acrimonious discussion of the topic in the general or DSP forum, so no problem either way.

Hi Jud

I would bet that the moment that I posted a reply about degradation of transparency due to further digital processing, that a few members would start posting sarcastic replies. The moment that you try to point out that digital isn't perfect, and that subtle low level, especially low level HF information, will be degraded , just as it is by USB cables and other things, then the fur would fly.

Since the creation of the DSP area there have been far fewer "religious" type flame wars.

Alex

[mkrzych]

What this generally refers to is the dynamic range mathematically afforded by the number of bits being used, not the actual real-world signal to noise ratio of the DAC or the system in which it's being used.

 

So, when figuring the noise floor, it is important to keep in mind that this is a measure of dynamic range (the maximum difference between the loudest and the softest sounds that can be captured.), not absolute noise levels (which will vary with actual listening volume on playback, and the actual SPL (Sound Pressure Level) at the microphone diaphragm during recording). Electrically, this parameter, is measured in dB as some level below 0Vu (representing full use of all available bits). Since this measurement equals both the loudest and the softest levels which can be represented by whatever digital system is being used, it is also referred to as the system's dynamic range. The noise floor of 16-bits is measured to be -96 dB (meaning that the level at which the noise is measured with no signal present is 96 dB below 0Vu. In 24-bit, that noise floor is technically around -144 dB. But in both cases, this is the digital specification only. Unfortunately, in order for digital audio to capture and play-back music, it must have analog stages before quantization (conversion from analog to digital) as well as after conversion back to analog. These stages vary, according to design, in their signal to noise ratios, and that must be factored in to the overall system's noise floor. While, with today's electronics (even op-amps) it is possible to get amplifier s/n (signal to noise ratios) of about -127 dB, this is rarely achieved. Where the problem comes into play is when one is trying to correlate the dynamic range of a DAC which is fixed by the number of bits available, with the audibility of that DAC's noise floor when listening to one's stereo. Obviously, the higher your playback volume, the higher the noise floor will be relative to your peak volume. The dynamic range of your system won't change, but it's like turning your volume all the way up with nothing playing. At some point your system's noise floor will reveal it self as hiss (and perhaps AC hum) in your speakers. Turn the volume control back to where you normally listen, and it's possible that you won't even hear hiss or hum when you press your ear to the speaker at that level. So real noise is relative. The point is that at normal listening levels of 80-90 dB*, the noise floor on any 16-bit or higher DAC will be below the human threshold of hearing and will be inaudible. I hope this is clear.

 

 

 

 

 

* Assuming the threshold of human hearing (at 1KHz) to be +05 to +10 dB (when 0 dB represents total silence) and +120 dB being the threshold of human pain.

 

Thank you so much George, that's clear now. However, I cannot hear anything when I turn my amp volume pot all the way up - it's dead silent in my case even I put my ear close to the speakers. So in theory if anything (nose floor, jitter etc.) is below let say 120dB it won't be audible at all and I think if you ever hear the hiss in your good system, it may be AC leak or some RF/EMI picked up by the cabling.

[sandyk]

I think if you ever hear the hiss in your good system, it may be AC leak or some RF/EMI picked up by the cabling.

 

Plug in almost any SMPS powered CD/DVD/BR player into an earthed power amplifier and you are highly likely to hear an audible hum at higher listening levels and SQ degradation at levels before that becomes audible.

[mkrzych]

Plug in almost any SMPS powered CD/DVD/BR player into an earthed power amplifier and you are highly likely to hear an audible hum at higher listening levels and SQ degradation at levels before that becomes audible.

 

Earthed you mean with 3-pin SCHUCKO connector? It is rare nowdays within consumer electronics.

[sandyk]

Earthed you mean with 3-pin SCHUCKO connector? It is rare nowdays within consumer electronics.

 

I have sent you a PM

 

Alex

[mkrzych]

I have sent you a PM

 

Alex

 

Saw it, will read it later. Thanks!

[gmgraves]

And it can't possibly interact with other low level material just above the threshold of hearing , or can it ?

Miska and others have already said that it is possible to hear things below the system's noise floor.

 

 

Yes, one can hear things below the system's noise floor, but I doubt seriously if one can hear things below the threshold of human hearing.

[gmgraves]

Thank you so much George, that's clear now. However, I cannot hear anything when I turn my amp volume pot all the way up - it's dead silent in my case even I put my ear close to the speakers. So in theory if anything (nose floor, jitter etc.) is below let say 120dB it won't be audible at all and I think if you ever hear the hiss in your good system, it may be AC leak or some RF/EMI picked up by the cabling.

 

 

There are lots of reasons for noise in a stereo system. In tube equipment, it's the thermal noise of the valves themselves, and in older equipment even the old carbon resistors contribute to noise. Self-noise from high gain stages, even modern solid state designs can contribute to noise. Of course power supplies can contribute thermal noise (hiss) and hum. If you hear nothing, when you crank the gain up, that's obviously a good thing. Of course, one can't dismiss the possibility that one is not hearing noise with the volume cranked up because (A) one can no longer hear those frequencies (we're all getting older) or (B) one's speakers can't reproduce those frequencies (less likely).

[sandyk]

Yes, one can hear things below the system's noise floor, but I doubt seriously if one can hear things below the threshold of human hearing.

 

And the first sentence of my reply ?

 

Of course, one can't dismiss the possibility that one is not hearing noise with the volume cranked up because (A) one can no longer hear those frequencies (we're all getting older) or (B) one's speakers can't reproduce those frequencies (less likely).

 

Mine is also as per the previous poster. Others with far younger ears than mine haven't heard any noise from the speakers either.

[gmgraves]

And the first sentence of my reply ?

 

I don't know, but I wouldn't think so. I've certainly never heard of such a phenomenon. If it does exist, It would be most likely due to intermodulation, which at those levels, should be pretty much non-existent. If it does exist, I would think that this would indicate a design flaw in the system's linearity. But again, I really have no knowledge of this.

 

Mine is also as per the previous poster. Others with far younger ears than mine haven't heard any noise from the speakers either.

 

In modern systems you shouldn't. I can't hear any noise from my system either, even with the volume cranked all the way up (except with phono selected - then I hear barely perceptible hum). My last comments were made more-or-less tongue in cheek, anyway.

[mayhem13]

Another thread collapses into a hole of supposition and speculation when the specter of real world physics emerges to challenge the self proclaimed and anointed.

 

Charlatans.

[sandyk]

Another thread collapses into a hole of supposition and speculation when the specter of real world physics emerges to challenge the self proclaimed and anointed.

 

Charlatans.

 

Most here would prefer to take notice of reports in this area by Peter St. and Miska, than from a self proclaimed "expert" who has been exposed to too close a proximity to sound reinforcement speakers over a period of many years.

 

Did I miss it, or haven't you yet been able to come up with those promised "revolutionary" desktop speaker designs ?

[Jud]

Another thread collapses into a hole of supposition and speculation when the specter of real world physics emerges to challenge the self proclaimed and anointed.

 

Charlatans.

 

Speaking of supposition and speculation, let me engage in some. I'm tossing this out in somewhat abbreviated form because I'm thumb-typing on my phone. As always, I very much welcome correction from those who know more.

 

- People with hearing aids can very easily have their understanding of speech destroyed by even relatively low levels of noise in the environment. (People on this forum with hearing problems, like Alex - sandyk- or Peter, appear to be preternaturally sensitive to at least some forms of distortion.)

 

- There are people (like my wife) who are much more bothered than others by white noise.

 

- Dither is applied (of course) at the level of the least significant bits.

 

- Correlated forms of noise or distortion are more audible/bothersome than uncorrelated, randomized forms. Randomized forms of noise may even be advantageous, as in the case of dither.

 

- When doing DSP, it is important to do it using bit levels below the least significant bits reserved for the signal. E.g., a 24 bit signal will be processed using 32 or 64 (or even higher) bit operations.

 

- Few or no DACs in use today are capable of noise levels below 21-22 bits, yet they are often processing 24 bit signals. I wonder if/how noise from the DAC at those levels interacts with dither, particularly any correlated noise.

 

- The signal from the DAC is amplified by pre-amps and amps that add their own distortions, as do the speakers or headphones. I wonder if this amplification exacerbates the problematic effects of noise, like the amplification done by hearing aids.

 

- Every step in the recording and playback chain adds noise/distortion. I am supposing the effect is cumulative to at least some degree.

 

- Obviously the cumulative noise and distortion of the chain must have audible effects, or we would not be able to tell the difference between listening to our systems and live music.

[beanbag]

you should start a new thread about it, then.

[mayhem13]

M

Speaking of supposition and speculation, let me engage in some. I'm tossing this out in somewhat abbreviated form because I'm thumb-typing on my phone. As always, I very much welcome correction from those who know more.

 

- People with hearing aids can very easily have their understanding of speech destroyed by even relatively low levels of noise in the environment. (People on this forum with hearing problems, like Alex - sandyk- or Peter, appear to be preternaturally sensitive to at least some forms of distortion.)

 

- There are people (like my wife) who are much more bothered than others by white noise.

 

- Dither is applied (of course) at the level of the least significant bits.

 

- Correlated forms of noise or distortion are more audible/bothersome than uncorrelated, randomized forms. Randomized forms of noise may even be advantageous, as in the case of dither.

 

- When doing DSP, it is important to do it using bit levels below the least significant bits reserved for the signal. E.g., a 24 bit signal will be processed using 32 or 64 (or even higher) bit operations.

 

- Few or no DACs in use today are capable of noise levels below 21-22 bits, yet they are often processing 24 bit signals. I wonder if/how noise from the DAC at those levels interacts with dither, particularly any correlated noise.

 

- The signal from the DAC is amplified by pre-amps and amps that add their own distortions, as do the speakers or headphones. I wonder if this amplification exacerbates the problematic effects of noise, like the amplification done by hearing aids.

 

- Every step in the recording and playback chain adds noise/distortion. I am supposing the effect is cumulative to at least some degree.

 

- Obviously the cumulative noise and distortion of the chain must have audible effects, or we would not be able to tell the difference between listening to our systems and live music.

 

You were all good till the last paragraph! Lol. Recorded music and live will never sound identical if you prescribe to the fact that nearly 50% of what we hear in our system is the reflected sound created by our listening space. Think of it as the third 'D' in 3d of which in this case of live vs recorded is a variable of infinite value. Noise has little or nothing to do with it IMO.

 

Maybe this is our saving grace reality here in that if we want it live, go see it live! Gets us off our duffs and keyboards to interact with the real world, instead of the cyber one that's become a false reality for so many. The Internet really is changing the world with a far greater impact than anyone imagined or many can comprehend.

[Miska]

I listen through headphones most of the time. So I get only venue acoustics, and no local acoustics layered over that...

[mayhem13]

Still doesn't get you that Memorex moment though, now does it? Engineers don't mixdown with phones so what you get is what you get....just another unexpected variable.

[sandyk]

Still doesn't get you that Memorex moment though, now does it? Engineers don't mixdown with phones so what you get is what you get....just another unexpected variable.

 

The best Engineers don't mix down ! Neither do they use compressors or limiters.

[mayhem13]

The best Engineers don't mix down ! Neither do they use compressors or limiters.

 

Complete and utter nonsense. Where do you come up with this stuff?

[Teresa]

The best Engineers don't mix down ! Neither do they use compressors or limiters.

 

Correct, the best modern engineers work for audiophile labels who believe in making natural recordings. All the work, microphone placement, balancing, etc. is done before the recording is made, they don't fix in the mix as that is what ruins the sound quality and liveliness of most modern recordings. Michael Bishop of Telarc does as little editing as possible and will only fix obvious mistakes, such as a bum note played, what was played in the auditorium or concert hall is what is released.

 

Even more pure are the recordings by DMP, their "Direct to Digital" CDs and "Direct to DSD" SACDs have NO editing within a track or song. If there is a mistake or other problem within a track the entire track is rerecorded. Tom Jung believes editing destroys the spontaneity of the music and that is why he never edits, his results prove he is right.

 

Complete and utter nonsense. Where do you come up with this stuff?

 

So, as you see with my response to Alex, his response was NOT nonsense but the truth and the reason many of us prefer audiophile recordings. There are many other great modern engineers who don't believe in destroying music with mix downs, compressors or limiters. Check out AudioQuest Music, Reference Recordings, Soundkeeper Recordings and many other modern audiophile labels that record music as it really sounds!

[mayhem13]

Fitting that you should post the same ridiculous summation as Alex. Clearly neither of you understand the recording, engineering or mastering processes.

[Teresa]

Fitting that you should post the same ridiculous summation as Alex. Clearly neither of you understand the recording, engineering or mastering processes.

 

It's not Alex nor I that is being ridiculous, it's you. And you are dead wrong. Of course that is nothing new for you. Read up on how real natural sounding audiophile recordings are made. Not audiophile remasters but recording companies who make audiophile recordings from the microphones to the finished product. These audiophile companies do not piss all over their recordings like the major labels do and they also are not part of the loudness war. Have you never tried a DMP, AudioQuest Music, Reference Recordings, Soundkeeper Recordings, Telarc, Channel Classics, Sheffield Lab, Crystal Clear or any of the other fine audiophile recordings out there?

 

I do understand the recording, engineering or mastering processes of the modern major labels and I reject their awful sounding recordings. Some of the major labels made good sounding recordings in natural environments from the mid-1950s to the mid-1970s but not today, for accurate modern recordings you one must turn to audiophile labels and their hands-off approach to recording which you have no clue exists. Well they do and many are quite wonderful.

 

Please don't talk about something you know absolutely nothing about, it makes you look like a fool.

[gmgraves]

It's not Alex nor I that is being ridiculous, it's you. And you are dead wrong. Of course that is nothing new for you. Read up on how real natural sounding audiophile recordings are made. Not audiophile remasters but recording companies who make audiophile recordings from the microphones to the finished product. These audiophile companies do not piss all over their recordings like the major labels do and they also are not part of the loudness war. Have you never tried a DMP, AudioQuest Music, Reference Recordings, Soundkeeper Recordings, Telarc, Channel Classics, Sheffield Lab, Crystal Clear or any of the other fine audiophile recordings out there?

 

I do understand the recording, engineering or mastering processes of the modern major labels and I reject their awful sounding recordings. Some of the major labels made good sounding recordings in natural environments from the mid-1950s to the mid-1970s but not today, for accurate modern recordings you one must turn to audiophile labels and their hands-off approach to recording which you have no clue exists. Well they do and many are quite wonderful.

 

Please don't talk about something you know absolutely nothing about, it makes you look like a fool.

 

 

You are certainly right that if you want new recordings, as opposed to digital reissues of recordings made in the 1950's and early 1960's, you won't find natural-sounding recordings among the "major" labels anymore. All the good recordings are done by independent recording organizations. In part, that's due to the fact that truly natural recordings are somewhat paradoxically best served by simple and sometimes inexpensive equipment, and that it's more likely that a studio control room full of the latest digital "toys" is a hindrance to natural-sounding recordings, rather than an asset to achieving that goal. Recording outfits with a cupboard full of microphones are likely to use them, and that's just wrong-headed. The more microphones used, the less likely it is that a recording will sound natural. Two good microphones, and a decent two-channel high-res digital recorder; either LPCM or DSD is all one really needs to make jaw-dropingly real sounding recordings. Even Telarc, at their best, tried to use calibration microphones in a C. R. Fine (Mercury Living Presence) arrangement to do most of their recordings. While they tended to use a fairly simple recording setup and many Telarcs sounded spectacular, they generally did not image very well; certainly, even though they tried, they did not get as good a result as Mercury did with the same three-mike spaced array configuration as did the Mercury team used, because Telarc used modern omni-directional mikes from B&K while Fine used early 1950's Telefunken model U-47s. While both the B&K and the U-47 were ostensibly omnidirectional microphones, the B&K as used by Telarc, was a real, modern omni pattern, and the U-47, with it's switchable modes (between omni and cardioid) was more of a quasi-omnidirectional mike. The difference is profound. The Mercury arrangement utilized the semi-cardioide pattern of the U-47 (when switched to the omni-pattern) to give a modicum of directionality to the pickup which resulted in the famous pin-point Mercury imaging and soundstage, while the pure omnidirectional characteristics of the calibration mikes simply could not capture that that level of image specificity. The results, as I said before, is that Telarc recordings never captured the level of soundstage magic for which Mercury Living Presence recordings were famous.

 

In today's world, the most natural-sounding recordings are made by Ray Kimber and his "Iso-Mike" process. The Iso-Mike process uses four closely-spaced, but acoustically isolated omnidirectional mikes to get spectacularly realistic results. Two of the mikes are pointed at the musicians, while the other two face the back of the hall. In the surround-sound mode, the two rear-firing mikes supply only ambience to the rear channels, and in the two-channel versions of the recordings, the rear-firing mikes are mixed into the front channel (at a reduced level, of course) to add an air of hall sound to the recording. These recordings are about the most natural sounding of any on the market today.