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In Reply to: RE: People here keep acting as if it is simple to hear a -120dB down signal. posted by Jaundiced Ear on September 12, 2014 at 00:58:38
Read up on acoustics, the dynamic range of the ear is reckoned to be 130dB or even better for some
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I assume that you use transistor amps because -120dB is between 1000 and 10 000 times lower than your typical valve amp distortion (0.1-1%).
If THD is that much higher there is no chance that anyone could possibly hear anything at -120dB as it would get completely drowned out by the distortions.
I suppose 0.0001% THD could be achieved by a SS amp if it uses vast amounts of negative feedback.
nt
If you get a tube amp to produce 130dBspl through your speakers you will not hear anything at -120dBspl because the distortion noise is 1000 to 10 000 times stronger.
Alternatively you could stand next to an air hammer and the chances are that you won't be able to hear the ticking of a watch you might be wearing.
While we can perceive noises or signals from a few dBspl to about 120+dBspl we can not perceive them if they are happening simultaneously. For simultaneous aural stimulation we can hear differences of about 40-50dB. Anything more than that and the lower one will be completely masked.
Similarly and using a Mahler crescendo of 120dB or more you won't be able to tell if the triangle is being played or not.
since of course if humans can only hear about -50dB into a song or signal that is playing then all the claims of hearing unmeasurable differences between power cables and USB cables fly out the window.
This explains why the Audio Diffmaker is such a bogeyman here. Inmates are afraid to even try it as it might upset their view of audio on two points: one, their ears aren't as superhuman as inmates think they are and two, the dratted machine can detect audio information the inmate could not.
Here's a thought experiment. How loud can a healthy NFL quarterback shout? I'm guessing after a lifetime of calling signals as a class they've got pretty strong voices. However, there are NFL stadiums that routinely have crowd noise measured at 130db when the visiting team is on offense. In those situations it's next to impossible for the quarterback to make himself heard by his teammates so clubs go to the so called "silent count" where visual signals are used instead. Pro football clubs certainly have no problem believing in audio masking.
JE
is just argument for the sake of it - no response.
'-120dBspl because the distortion noise is 1000 to 10 000 times stronger'
1. Where did you get those numbers? The same place where creators of MP3 codec got theirs, along with masking they love to talk about? Why did it fail so miserably then in their case, even at the highest bit rates, to sound exactly as CD, with its measly 96 dB of dynamic range?
2. Are you able to hear a difference between power cords, interconnects, USB cables, media players on PC, ASIO vs. KS vs. WASAPI etc.? If not, I respectfully suggest doing something about it, like ASAP. But, if yes - what would be your guess, how far down below (in dB) the measured differences would lie?
Klippel test of added distortion. Easily heard through my system down to 0.5%THD (-46dB).
Which is why I would not ever employ a valve amp of any kind, I want my electronics to be at least one order of magnitude below my speakers when it comes to adding distortions of any kind.
I do not use mp3s since they sound horrible. I don't even use lossless codecs.
I also do not use USB except to connect my keyboard and mouse to the computer.
USB is a deeply flawed and inelegant way to stream anything.
And while I fairly easily hear differences in amps or convertors I have never heard any between standard, decent interconnects or speaker cables and more expensive ones.
I have no idea about ASIO, KS or WASAPI since none of that stuff exists on my computer.
However I do remember ASIO from a couple of decades ago and it was shit and lacking in elegance in design, very much like USB.
I doubt even the best listening rooms of Asylum board users is better than around 20-30dB above absolute zero ambient acoustic noise levels. How are you going to hear that -120dB signal with a system set up for playing a typical bit of program even if you had one of the best rooms? The math apparently isn't supporting the idea. Sure you can gain up the noise enough to hear but if you throw a CD on when it's turned up that loud something will fail whether it's your system or the building supporting it. Not a practical situation at all. What's the point?
Edits: 09/12/14
"I doubt even the best listening rooms of Asylum board users is better than around 20-30dB above absolute zero ambient acoustic noise levels."
The confusion comes between broadband noise levels (according to some weighted curve) and narrow band noise levels. If there is no operating HVAC system running and noisy appliances are not in use, rural settings will have little or no noise in the frequency range where human hearing is most sensitive. In addition, it is possible to hear single tones that are as much as 20 dB below the broadband noise floor. Except for low frequency noise or when appliances or HVAC systems are running, what one can hear is going to depend on volume control settings, the recordings on plays and the sensitivity of one's ears, not room noise.
As to those volume control settings, and so as to be accused of not cheating, peak sound pressure levels at live orchestral concerts have been measured at over 120 dB (e.g. Mahler symphonies, row 5). A dynamic range of this amount is required for realistic reproduction of this music. Some of us have systems with this peak capability throughout most of the frequency range applicable (except possibly for organ pedal notes). And some of us turn up our volume controls to achieve these realistic levels.
Some sounds, for example jangling keys, have peak to average sound levels that are greater than 30 dB. Dropping one's keys on a stone floor can produce peak SPLs of 140 dB, but there will be no building collapse. I have played such a recording at volume control settings that I normally use for playing orchestral music and the jangling keys were not even at natural volume levels.
Tony Lauck
"Diversity is the law of nature; no two entities in this universe are uniform." - P.R. Sarkar
" If there is no operating HVAC system running and noisy appliances are not in use, rural settings will have little or no noise in the frequency range where human hearing is most sensitive. In addition, it is possible to hear single tones that are as much as 20 dB below the broadband noise floor."
I would have guessed most Asylumers are urban to suburban but don't know. I never get near complete silence around here that I can remember. When it gets really quiet my ears agc starts cranking up the gain and I still hear noise.
Are you expecting your noise floor to be single tones, or that people want to try and listen to program material below the noise floor? Neither situation seems likely.
"A dynamic range of this amount is required for realistic reproduction of this music."
I don't really know what your listening to but none of the recordings I have use anywhere near 120dB dynamic range as part of the presentation. Even if you were super exceptional and managed a normal listening unfiltered ambient listening position room noise level of +10dB of whatever band you like, which there is very little likelihood for most I'd guess, you'd still need 130dB output at the listening seat to be able to to be guaranteed to hear it all of a 120dB dynamic range show. Sounds a little brutal to me.
"Dropping one's keys on a stone floor can produce peak SPLs of 140 dB, but there will be no building collapse."
I'd imagine if you could sustain say 140- 150dB unfiltered whiteish, around 10-10kHz, noise with fairly even distribution throughout most structures you'd start having problems. Again, this is just a guess but it sure sounds like a fun experiment I may never get to try.
I'm sorry for you if you never get silence. Not only is it bad for listening to music, it is bad for health. Where I live if I shut off my appliances I get silence, as there are few neighbors around most days. On a non-windy day the only outside noise I hear are roosters, ravens and geese, plus seasonal lawn mowers and snow plows. The "main" rood is 200 yards away and it has little traffic outside of ski season. Last week was a bit noisy, as the road was repaved.
The dynamic range created by musicians in a symphony orchestra (loudest tutti attack vs. quietest solo sustained note) is about 55 dB. However, in the pauses between notes there is hall decay down to the threshold of audibility. The actual dynamic range experienced by the listener will depend on how quiet the hall is, where the listener is sitting, etc. but can be 120 dB. Hearing all the decaying ambiance may not be necessary to enjoy the music, but it's there and if it can't be heard in a recording this aspect of realism will be lost. It is possible to achieve this level of dynamic range using high resolution digital formats and suitable low noise microphones. You should be able to hear residual hall noise from the recording venue on the recording, not hum or hiss or other recording or system artifacts.
I checked and I can reliably hear a 1000 Hz tone recorded at a level of -100 dB (96/24) using volume settings that I customarily use to playback large scale orchestral recordings. I didn't shut off any appliances, but I did close the door to my listening room. My computer is not completely silent, so I couldn't do much better than this due to fan noise and possibly disk noise. I will try this again on another occasion, this time using a silent computer and powering down everything in my home other than the computer and audio equipment.
We don't have to "try" to listen to sounds below the noise floor. If we didn't have that ability we wouldn't be here today, as our ancestors would have been eaten before they reproduced.
Tony Lauck
"Diversity is the law of nature; no two entities in this universe are uniform." - P.R. Sarkar
"...it is possible to hear single tones that are as much as 20 dB below the broadband noise floor."
That's why I used Morse Code as a HAM Radio operator when I was a kid. One could audibly decode a series of weak dots and dashes (approx 1KHz tones) in the noise floor where normal voice transmissions would be unintelligible.
Additionally, the audio bandwidth required for voice transmission (SSB) was about 2KHz so 2KHz bandwidth filters were used. Dropping the filter bandwidth also improved signal-to-noise ratio, dropping broadband noise by nearly another 10dB by using narrow filters CW (Morse Code) vs ~2KHz for SSB voice.
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