Originally Posted by amirm
Back to psychoacoustics, we have two ears which are separated by some distance. The sound from the speaker hits the reflector arrives a the ears at two different times. The head also blocks the sound for the other ear causing some filtering and hence, modification of frequency response. These two differing sounds is then presented to the brain which has to make sense out of it. Contrast this to a microphone which only picks up one sound and computer measurement and graph such as ETC that without interpretation shows said signals. What the brain interprets and what the graph shows are two different things. The former cares about the spectrum for example due to filtering just mentioned. The latter, only shows reflection energy and time. And again, represents only one signal, not two. Here, you absolutely want to listen to Dr. Toole because his background is psychoacoustics and his conclusions formed from countless listening tests:""It seems obvious to look at reflections in the time domain, in a “reflectogram” or impulse response, a simple oscilloscope-like display of events as a function of time or, the currently popular alternative, the ETC (energy-time curve). In such displays, the strength of the reflection would be represented by the height of the spike. However, the height of a spike is affected by the frequency content of the reflection, and time-domain displays are “blind” to spectrum. The measurement has no information about the frequency content of the sound it represents. Only if the spectra of the sounds represented by two spikes are identical can they legitimately be compared.
All of this is especially relevant in room acoustics because acoustical materials, absorbers, and diffusers routinely modify the spectra of reflected sounds. Whenever the direct and reflected sounds have different spectra, simple broadband ETCs or impulse responses are not trustworthy indicators of audible effects."
Dragon talks about using the right tool and understanding acoustics yet he doggedly ignores said advice in constantly recommending using ETC, dealing with reflections based on how strong they are vs whether they are perceptually beneficial or not.
The best thing you can do for your room and your knowledge of audio is to buy Dr. Toole's book. And if you possibly can, spend a day with him at his training classes at CEDIA (next one in September). The man is an excellent teacher on the top of his 40 years of knowledge and wisdom in this space. For a free teaser and a sliver of what you will learn, here is a good audio interview: http://twit.tv/show/home-theater-geeks/14
So we are again presented with the same cut and paste by another marketer who has absolutely no acoustics background and who has never himself actively taken measurements, let alone time domain measurements. But hey, he has read a book and now seeks to market solutions based upon his finally reading one book.
He likes to name drop and denigrate "my opinions" that apparently have no foundation in either physics or psychoacoustics as he is incredibly ignorant of just who was principally responsible for the development of such ideas. The irony is that every one of the, say 25, additional acousticians responsible for the development of such ideas are each responsible for more than what Toole and Olive have accomplished in their careers. But such is what one comes to expect when the person commenting is unaware of a first hand contextual history and who only knows what a book tells him.
You see, Toole asserted the same notion about the ETC back in the late 1980s, and it promptly went nowhere. The reason for this was apparent them with folks intimate with the process (just as was the inappropriateness of using statistical calculations for reverberant sound fields in small acoustical spaces were - along with an awareness of how such RTxx measurements must be taken with an omni source, which no one here has yet done...So, isn't it amazing that those who talk of using measurements and subsequent RTxx calculations don't even employ the proper procedure???)
So Microsoft Bob maintains that ETCs are not an appropriate tool as they are a time domain tool and do not focus primarily upon the frequency domain. Duh!
Why is this an issue or not?
Let's stop and look. As he continues this objection over and over without much awareness of how the tool is actually used, seeing as how he has never made measurements and how the book does not explain the process to the degree sufficient for him to understand...
So why is this important or not important?
Let's examine the environment in which such measurements are taken. One principal that was important for many years before Toole became involved in this is precisely the nature the nature of the boundaries (specifically, their acoustical impedance) that were of considerable concern. Likewise, this same concern extended to any treatments. (Now contrast this fundamental focus with those who are now just becoming aware
that such characteristics can even be a variable deserving attention!)
You see, the great attention was spent by the acousticians to insure that the boundaries were broadband in their behavior, meaning that essentially from the specular frequencies upward that the boundaries treated all of the specular energy equally. What was incident on the boundaries all reacted uniformly, either being absorbed or reflected or diffused as evenly as possible. Thus the boundary did not have the effect of EQing the incident sound by unevenly interacting with it. As long as boundaries and boundary treatments are broadband, no uneven processing of incident energy occurs.
So, if the boundaries evenly process incident energy, we do not have a problem. And any problem we do have with reflected energy can be further modified with broadband treatment.
We only have a problem if said boundaries unevenly processed the incident signal and resulted in the effective EQing of the reflected signal, thus resulting in a resultant emission that was unlike both the direct and boundary incident signal.
Ironically, Toole is also in agreement with this concept and opposes the ALL TOO COMMON use of treatments that do not perform ion a broadband manner. Ironically, when we presented such a concept in the form of information concerning just how thick the common porous absorption needed to be everyone had a hissy fit complaining that it was just too thick and took up too much room, and subsequently insisted that it would be fine to use less as the effect was just as good as using the thicker stuff. thus the consensus on this forum is that they need not utilize broadband treatment and that using whatever is convenient and acceptable to the wife (as opposed to stuffy acousticians) works fine without problems - in fact, the benefits far outweighed any imagined' problems! But amazingly, MS Bob was silent on the issue, presumably as he had not finished reading his first 'acoustics' book.
So why does MS Bob have his panties in a wad over this issue?
Apparently the rooms in which he spends his time have all sorts of boundary materials and treatments that feature non-broadband behavior and thus effect indirect incident energy in a manner that effectively EQs it, rendering the reflections different in tonal composition than the direct incident energy. This IS a problem.
However, it is not a problem with the ETC. It is a problem with process and, quite frankly, ot os a problem as a result of lousy flawed planning and inappropriate treatments.
The irony is that the ETC CAN be used to analyze the time domain behavior if energy specifically by frequency band simply by using band limited ETC measurements. These are a useful investigative tool in order to determine if there is a problem with the boundary reflectivity. So all of the objections offered by one who has never used the measurements or actually performed an analysis are bogus.
The fact is that this capability was a fundamental capability introduced with the first ETC measurements introduced by Dick Heyser (another insignificant acoustician)in the 1960’s. And they are a great investigative tool IF one suspects that the boundary or treatment does not operate in a uniform broadband manner.
But seeing as a fundamental criterion for the design of boundaries and for the design and use of treatments is that they be broadband, once this consideration is met, there is no need to keep bringing up the use of band limited ETCs. But notice how MS Bob KEEPS incessantly harping on the need for this – apparently obviating the problem that the boundaries and treatments with which he is mistakenly concerned are NOT broadband!
The solution is not to jettison the tool, but rather to get one’s act in gear and to design and employ the proper boundary and treatments!
And then he brings up the OLD topic of binaural perception. It is nice to see he has read an article mentioning this behavior, as it too is a well understood behavior that is also easily measured and examined and which has been researched in depth. Ironically much of this research was made possible by those folks MS Bob likes to ignore in conjunction with the TEF analyzer! Carolyn (Puddie) Rodgers seminal research on the effects of the pinnae and similarly research such as that performed by Dr. Peter D’Antionio using dual TEF analyzers to analyze the interaural cross correlation (IACC) is apparently unknown as he simply chooses to selectively ignore it – as it was not mentioned in the single book he read. Fortunately the results are fundamental to those who actually have studied the phenomena.
And if one does want to investigate this themselves they can rather easily do it with a dual channel FFT such as ARTA. But it speaks volumes that he has neither pursued that which he claims is such an important topic himself or even become familiar with the actual research! But as a result of reading a reference to the subject in a limited text, he fancies himself now qualified to pass judgment on others who have been involved in such research and who are also well aware of it.
And if must confuse him to no end to realize that in a space featuring the recommended left-right symmetry, that such differentiation is minimal (well behaved) and quite natural. It only becomes a more complex and significant if the best practice of L-R symmetry is violated. So while its basic role in localization is important, unless someone makes a mistake in design and fails to follow best practices such as those mentioned regarding broadband responses, while it is great that he has now become aware of the issue, it is largely moot. But hey, some are continually amazed to find the world is larger than they had previously been aware. And his discoveries have just begun.
So, not only is his description of the power of the ETC extremely limited, greatly understating what it, and especially what it in conjunction with a few other measurements can depict in great detail, but his preoccupation is that its common use assumes a properly designed environment where both the boundaries and treatments are properly designed and implemented, and whereupon when then worry about their proper application and placement to achieve a desired result.
For you see, at that point, a properly designed room is far past the point of determining if boundaries are properly broadband and if the treatments to be utilized are properly broadband. It assumes that the operators are thoroughly versed in acoustics best practices and that they do not need to suddenly become preoccupied in the final stages with factors that should have properly been fundamentally addressed in the preliminary stages when the basic analysis of the characteristics and behavior of the space was properly conducted.
But seeing as simply reading a book pushing a particular approach does not adequately represent the larger world of what is best practice based upon what is actually known and done, it is of little surprise that MS Bob would be unaware of the basic tenets that, while he makes mention of them, he then fails to implement, which then results in a straw man concern later in the design and treatment process, As using broadband concepts are fundamental, and not a last minute Band-Aid requiring last minute band limited analysis as he falsely asserts – unless perhaps if you are adhering to one of his ill conceived projects where he aptly asserts that such issues are still concerns long after they should have been properly addressed. You see, the fact that he is still addressing mistakes in process is neither a fault nor limitation of the measurement but rather an indication of the lack of awareness and understanding on the part of the operator.
And this issue was already well understood when Toole himself originally became aware of it in the late 80’s. And it is no wonder that the response was an overwhelming “Duh, of course”, rather than some histrionic panic to adopt something that was already a fundamental concern addressed long before.
So, to paraphrase Don Davis: “The ancients keep stealing all of our inventions.” But I guess one should be encouraged to see a few more FINALLY become aware of factors that others have considered as fundamental for over 40 years.Edited by dragonfyr - 6/18/12 at 11:58pm