Gee, thanks Todd.
> One last thing, we are all getting frustrated by the redundancy,
Sigh...yes.
> This was Roy's first post to the max-noise list:
And I want to note, that I never saw this post, as I was not a participant
in this list...choosing family time and vacation over arguing about
this...but it appears to be a direct response to only my comments made on
other lists...so, I, unfortunately, believe it is necessary to correct
whatever misunderstandings or mis-statements have been made here.
>
>
> First of all I'd like to commend Austin for his explicit statement of this
> interpretation of the Higgins text. Its too bad that Higgins wasn't as
> explicit about what he meant when he wrote the book.
Higgins WAS explicit, VERY explicit in fact. There are only TWO terms used
in the accompanying equation:
DR = 20log10(largest/smallest discernable signal)
So, we ONLY need definitions for the terms "largest", and that is CLEARLY
labeled on the diagram as:
>"largest" is shown on this diagram to be the maximum signal level minus the
>minimum signal level, and is the largest range or absolute range that the
>signal can go from <=> to.
and:
>"smallest" is shown as the noise. It is the same thing as "smallest
>discernable signal", which means the smallest change that can be detected.
Note that the ONLY reference to "smallest..." in any of the text, IS
"smallest discernable signal", so there is NO question that "smallest
discernable signal" and the "smallest" listed on the accompanying diagram
mean the same thing, simply the diagram labeling was shortened.
> As the scan of the
> diagram shows, the labeling of the diagram is fairly spare.
So what if it's labeled sparsely? There are only two terms it's showing
here, and those are the only two terms used in the accompanying dynamic
range equation, so no more labeling is required. The book is explicit in
using the two terms, largest and smallest, and the diagram IS explicit in
their meaning. Anything more would be superfluous.
> I'm quite sure that this is NOT the interpretation that Higgins
> had in mind
> while writing the book.
It is EXACTLY what he meant, and there is NO interpretation required at all.
Largest and smallest are CLEARLY shown as to what they are. These terms,
when left undefined, CAN be ambiguous, but in the Higgins
book/equation/diagram, there is NO ambiguity at all.
> I'd like to be equally explicit about the correct
> interpretation with supporting logic behind it.
Oh, my hero!
>
> ------------------- Interpretation of Higgins text.
>
> I'll begin with the fact that we're talking audio here. An "audio signal"
> is a wave form not a single DC voltage. When you measure the size of an
> audio signal what you measure is the amplitude of the wave form.
> In the
> left half of the diagram we see an audio signal that spans the
> whole record
> groove, the label "largest" is the amplitude of the largest possible wave
> form i.e. amplitude of the largest possible signal
Funny, that's exactly what I have always said, and say above. I'll show it
again here for clarity:
"...and is the largest range or absolute range that the signal can go from
<=> to"
"largest range" and "absolute range..." are EXACTLY the same as amplitude.
> ...or maximum
> audio signal.
Well, that's an ambiguous term. Maximum as referenced to what?
> The right half of the diagram shows a very small audio signal amplitude.
> This term "smallest" or "smallest discernible signal" denotes the
> amplitude
> of the smallest audio signal (a wave form) that is discernible above the
> noise level.
That's fine, and doesn't disagree or negate what I've said at all.
> This might also be called the minimum audio signal.
That's ambiguous, just like maximum is. Minimum as in what, lowest signal
level, or smallest discernable signal anywhere in the range as limited by
noise?
> So the ratio that you end up with is:
> (amplitude of the max signal) / (amplitude of the min signal)
>
> or in totality:
>
> DynamicRange (db) = 20*log10((amplitude of the max signal) /
> (amplitude of the min signal))
> with audio signal measured in voltage.
But that depends on what you mean by "min". If by min, you simply mean
smallest discernable signal, that is correct, and is in agreement with
exactly what I've always said.
You haven't corrected ANY of my definitions or understandings, so I fail to
see your actual point here.
> What this gives you is simply the range of audio signal levels where the
> audio system is operating within spec.
The dynamic range spec number does not indicate ANY "range" whatsoever. It
characterizes a signal OVER a range based on noise. "Operating within spec"
has nothing to do with anything in this discussion.
> In layman words, this is the
> definition of dynamic range -- the range of audio output from softest to
> loudest.
No, it is not the RANGE of audio output. It is characterized OVER a
particular range, but does not denote any particular range at all.
> ------------------------
>
> This quite obviously is very different from Austin's interpretation.
What is quite obviously very different? You gave the EXACT same definitions
I gave for "largest" and "smallest" and the dynamic range equation is in
plain type. I see nothing corrected, you merely gave you own definitions of
the same thing.
> The
> numbers may be close much of the time but getting the principles
> accurate is
> crucial if we are to apply similar principles to completely other areas of
> interest (not audio). Austin, you may now be thinking wrong, wrong, wrong
> but ... please, please, please read what I am saying. Understand what I've
> written first, don't merely deny it.
>
<snip superfluous "stuff">
> I assume your field has to do with digital signal processing or something
> close.
My "field" has to do with every aspect of imaging/audio (to name a few)
system design, not just DSP or something close.
> When you digitize any signal you end up with discrete numbers and
> discrete levels. The digital representation is designed to be a "good
> enough" reproduction of the original using discrete levels.
It's not simply "good enough", it's that resolving down to noise is all the
valid information you are going to get from a film scanner, period. It IS
as good as you can do. Different circumstances, such as sonar echo
processing (which I have done) DO benefit from digging into the noise...but
film scanners do not.
> However, the
> real analog signals have no discrete properties. They are completely
> continuous.
No they are not. All analog signals have what can be considered
"resolution", as defined by noise. You can NOT measure .0000001V in a
system that has .1V of noise. EVERYTHING has the ability to be resolved,
period.
<more snip>
> -------------------------
>
> At this point I'd like to just go through various problems with your
> interpretation and site references that agree with mine.
Well, one of the problems we seem to have is that just because you say
something agrees with you, or disagrees with me, doesn't mean it does...
What if they agree with both of ours?
> This basically
> boils down to what the preponderance of the evidence shows. I highly,
> highly recommend printing out this whole post, taking it and the Higgins
> book and discussing it with your friend Kennedy and any others
> whose opinion
> you respect.
I have discussed this with Kennedy and others I respect, and every one of
them agrees with my understanding. They simply don't understand what about
this you just don't get, and why you are even arguing with me about it.
> -------------------------
>
> Back to your interpretation of the DynRange definition/formula. You are
> transforming the denominator from "smallest discernible signal" into
> "smallest discernible signal increment".
Whether it's the "increment" or not is determined by what ever the limiting
factor is. BUT...you (typically) ONLY resolve down to noise, which is why,
typically, noise IS the "increment". Do you believe you can resolve a
scanner signal further than to noise, and that you get useful information
from that?
> The text makes no hint of
> increment, difference, or anything of the sort.
How then is it determined how many bits are used to represent a particular
dynamic range? It's solely the INCREMENT and the OVERALL RANGE, in other
words, the noise and the amplitude. If there was no resolution component of
dynamic range, then why is that what IS characterized when digitizing the
signal????? In fact, it's the ONLY thing that is characterized.
> The noun in the
> denominator
> is "signal", pure and simple, so you ought to be measuring a
> "signal" not a
> difference or increment. The word "discernible" simply means detecting or
> discerning signal above the noise,
No, it simply means discerning it from something else, not necessarily
noise...but from another signal, possibly separated/limited by noise.
> but you are turning it into
> "distinguishability" of one level of signal from a different level of
> signal, where that increment is the "noise" of the system.
That completely fits the definition of "discernible", and my use is the
correct use of it in this case.
Definition of "discern":
"To perceive or recognize as being different"
> The
> very notion
> of the existence of such an increment is impossible. This gets into the
> exponential nature of audio.
What exponential nature of audio? We are talking about signals and VOLTAGES
here. Over the voltage range, the noise will be pretty much the same,
therefore, the ability to discern signal is the same throughout the entire
range.
The signal we ara characterizing is NOT exponential, it has a FIXED overall
amplitude and a FIXED noise. There is NOTHING exponential about these
numbers. The characterization of these numbers can be done using
exponential numbers, but that has nothing to do with this.
> Suppose an amp that goes from 1 watt to 100
> watts of output power. The power increment from 1 watt to 2 watts would be
> easily distinguishable however going from 99 watts to 100 watts would be
> impossible to distinguish. -- Basically, distinguishability is
> based on the
> RATIO of the two wattages NOT the DIFFERENCE.
But I NEVER said you would do the distinguishing that way for a power amp.
It's YOUR example, not mine. You are confusing log issues with non-log
issues. When dealing with characterizing a VOLTAGE, the increment IS a
"fixed" "difference".
> ------------------------
>
> Here's a web reference that YOU picked and said supported your case.
>
>
>
> The first couple of paragraphs talk about DyR and number of bits in
> agreement with much of your DSP statements. Further down though is the
> equation for Dynamic Range. Have you checked it out?
>
> DynamicRange = -20*log10 (noise level rms/maximum level rms)
>
> The minus sign just flips the ratio. So "maximum level rms"
> corresponds to
> "largest" -- and is NOT max - min. Also note the "rms" which you should
> know is root mean square, exactly as I wrote above, and certainly implies
> that "signal" means a AC audio signal.
This is all a "so what". That doesn't negate anything I've said. You are
confusing A/C signals, which are typically stated as an amplitude, and D/C
signals, which are typically stated as a range with two bounds, like -3V to
+3V, or as a single number, with zero as the other bound.
An A/C signal of 6V is the EXACT same as a D/C signal of -3V to +3V.
This has, for some reason I can not even fathom, been a big deal for you to
understand....you've wanted to fuss about this "max - min" vs "max" thing,
and it's a NON ISSUE.
Do you somehow not believe you can find the dynamic range of a DC signal???
<snip references>
> Here's why we use the adjective "Dynamic":
>
> Dynamics - 1) The amount of fluctuation in level of an audio signal. 2) In
> music, the playing of instruments loudly or softly at different times.
...#2 really has no bearing on this discussion.
"dynamic" is used in "dynamic range" simply because it is a characterization
of the "dynamics" of a particular signal (dynamic meaning characterized by
continuous change).
Dynamic range is the characteristics of A dynamic aspect of A signal OVER A
range, it is not a range in and of it self.
> ------------------- Summary
>
> ...In all of them, Dynamic Range is a range of values
No, it is a single number, NOT a range. That number is characterized OVER A
range, but that does not make dynamic range A range.
> where
> the system is working as advertized.
What does advertising have to do with anything?
> The range is specified by a
> maximum and a minimum value.
If it was a range, it would be...but dynamic range is NOT specified by a
maximum AND minimum value...it is a SINGLE value characterizing a maximum
and minimum value...and again, that does NOT make dynamic range A range, but
does make it a characterization OF a range.
> All values within the range are possible
> as far as the real world is concerned i.e. the range is a continuous
> range.
No. Measurements are only valid down to noise. You can NOT accurately
resolve a scanner CCD input meaningfully to less than noise.
> Digital systems are used just about everywhere now and the
> digitization may quantize values within a dynamic range. This may
> make it appear that there are discrete, distinguishable values
> within a range, but this is purely an artifact of the digital
> implementation and digital representation of the data.
That's just not true. People have been using characterizing signals for
many years, before digital, "down to noise".
> It is no way
> changes the basic concept of dynamic range -- there are no discrete
> levels, and there is no notion of dynamic range being a "number of
> levels".
What is the dynamic range of an 8 bit number? How many different "levels"
can be expressed by an 8 bit number? CLEARLY dynamic range and "number of
levels" are DIRECTLY related, or any number of bits could represent any
dynamic range, and that's just not the case. Any number of bits can
represent any DENSITY range, but NOT any DYNAMIC range.
>From a cursory view, I didn't find anything in your references that
disagreed/negated what I've said.
You also claimed my "definitions" of the Higgins diagram and equation were
wrong, yet your "correct" definitions were the same. Where were the
"corrections"?
Austin
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