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Topic: 15 Haydn_ String Quartet In D, Op_ 76, No_ 5 - Finale - Presto 3 best (Read 9953 times) previous topic - next topic
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15 Haydn_ String Quartet In D, Op_ 76, No_ 5 - Finale - Presto 3 best

Reply #25
I don't think so, I can repro this graph in iZotope RX or other spectrum analyzers. Perhaps you forgot about variance, the attached spectrum is clearly time-averaged.

These spectrum analyzers don't display density, they assume distinct peaks (tones) which noise is not and plot amplitudes instead. Noise may be over- or underestimated depending on all the parameters (window, fft size, Fs ...).

Noise density of 16/44.1 with TPDF should be around -137 dB. (I was too tired yesterday, so I was a few dB off..)

For example in the 1/3rd octave 4 kHz band this noise density would add up to -107 dB.
For DSD 2.8 it would be roughly -127 dB. Of course this gets worse. Absolutely worst would be the 30 kHz band with the tons of noise DSD 2.8 is producing up there.
"I hear it when I see it."

15 Haydn_ String Quartet In D, Op_ 76, No_ 5 - Finale - Presto 3 best

Reply #26
Ah, gotcha. Sure, I actually don't know any spectrum analyzers that display density. Most of them display amplitude of FFT bins, nothing more.

15 Haydn_ String Quartet In D, Op_ 76, No_ 5 - Finale - Presto 3 best

Reply #27
I wonder if the strange notches in the DSD noises have special meanings? They don't look like traditional equal loudness contours and other noise shaping curves as shown in Alexey's research.
http://audio.rightmark.org/lukin/dither/dither.htm

15 Haydn_ String Quartet In D, Op_ 76, No_ 5 - Finale - Presto 3 best

Reply #28
I wonder if the strange notches in the DSD noises have special meanings? They don't look like traditional equal loudness contours and other noise shaping curves as shown in Alexey's research.
http://audio.rightmark.org/lukin/dither/dither.htm

I bet it's the response of the noise shaping filters. Most digital filters have massive notches in their stop-bands where the "zeros" are. They're assumed to be irrelevant, because though the response theoretically drops away to -infinity at these points, it's always falling from an already inaudible -100dB or so.

To put it another way: when digital filters are designed to attenuate by, say, 100dB, that's the minimum attenuation; -100dB is the most signal that will get through. At the "zeros" (i.e. the frequencies at which the stop band response is pinned down), it will be "almost" infinitely attenuated.

Graphs don't normally have axes that let you see this, but it's usually there.

Cheers,
David.

15 Haydn_ String Quartet In D, Op_ 76, No_ 5 - Finale - Presto 3 best

Reply #29
Does anyone here have experience with string quartet sound pressure levels ?
The Stuart paper states:
Quote
For a system gain of 75dB, the loudest peak passage was measured as 102 dB SPL at the listening position, somewhat lower than the level we would expect from a live performance at a distance of 3 m. This level was chosen for comfort, and because it was high enough for details to be audible but also low enough that 16-bit RPDF dither would be inaudible at the listening position

I have read another study about "Loudspeaker Simulation of a String Quartet for in situ Listening Evaluation"
http://www.acoustics.asn.au/conference_pro.../Papers/P2a.pdf
Quote
At the end of the recording session, the A-weighted, peak sound pressure level was measured with a B&K 2260 sound level meter, fast setting, approximately 4m in front of the quartet. This measurement (78dB) was used to roughly calibrate the playback level during listening evaluation.

While I can accept differences between string quartets, measurements and acoustics, the difference between 102 dB and 78dB (both peak) is very large. It indicates to me that the Stuart test might have played the recording at a higher than realistic level.

15 Haydn_ String Quartet In D, Op_ 76, No_ 5 - Finale - Presto 3 best

Reply #30



(supposedly from Andreas Koch's DSD seminar powerpoint presentation)

edit: previous image added on top for better comparison

edit: plotting SNR as a flat line vs. the noise spectrum of DSD noise, (dis)ingen(u/i)ous!
"I hear it when I see it."



15 Haydn_ String Quartet In D, Op_ 76, No_ 5 - Finale - Presto 3 best

Reply #33
Does anyone here have experience with string quartet sound pressure levels ?

Lots...just with my ears.
The only time I've ever been 3m away, would be at recitals in the practice rooms outside the main concert hall. 3m from the front row to performers on the main stage...no way!
Next time I'm in such a scenario I'll do some A weighted measurements with my Sony Z1 using Audiotools and an external Dayton mic.
102db seems incredibly loud for such a scenario. Now I'll have to figure out a way to get them to play some Haydn. 

cheers,

AJ
Loudspeaker manufacturer

15 Haydn_ String Quartet In D, Op_ 76, No_ 5 - Finale - Presto 3 best

Reply #34
The DSD graphs that I posted are just one typical example. Noise floor of DSD depends on the encoder used. The noise shaping algorithm of some encoders creates notches in the noise spectrum, others are more flat. Here's a comparison of few encoders: A Comparison of DSD Encoders & Decoders.

15 Haydn_ String Quartet In D, Op_ 76, No_ 5 - Finale - Presto 3 best

Reply #35
It should also be noted that because DSD is not a properly dithered quantization, the noise floor varies with the signal and contains some amount of nonlinear distortion (but is still below the floor of 16-bit TPDF-dithered quantization).

15 Haydn_ String Quartet In D, Op_ 76, No_ 5 - Finale - Presto 3 best

Reply #36
The DSD graphs that I posted are just one typical example. Noise floor of DSD depends on the encoder used. The noise shaping algorithm of some encoders creates notches in the noise spectrum, others are more flat. Here's a comparison of few encoders: A Comparison of DSD Encoders & Decoders.




Thanks. After seeing your link it is very clear that this graph is misleading because it implies noise floor of all 24-bit PCM formats below 20kHz are higher than DSD64.


15 Haydn_ String Quartet In D, Op_ 76, No_ 5 - Finale - Presto 3 best

Reply #38
Thanks but I am referring to the theoretical spec, not actual AD/DA performance. Just like RMAA can generate 24-bit signal with -145dBFS noise and -180dB noise shown in spectrum graph but no current AD/DA can achieve this performance.

But now at least I know that the notches in DSD noise is not a "trademark" of DSD because it is only Korg's characteristics.

15 Haydn_ String Quartet In D, Op_ 76, No_ 5 - Finale - Presto 3 best

Reply #39
The DSD graphs that I posted are just one typical example. Noise floor of DSD depends on the encoder used. The noise shaping algorithm of some encoders creates notches in the noise spectrum, others are more flat. Here's a comparison of few encoders: A Comparison of DSD Encoders & Decoders.


Hmm... maybe out of subject but, how it would be with 16/44.1 sources (meaning if one would like to ABX CD vs DSD ... how's that done)?


 
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