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In Reply to: There is no question that laboratory measuring devices are far more sensitive and accurate than our hearing... posted by McCormack on February 14, 2007 at 15:19:06:
Your ear is really a poor transducer, though it has an incredible analyzer hooked up to it. Hell, even my dog can hear far better than any human I know. A tiny example of what an acoustic lab can do without effort, yet you couldn't possibly do: I was in a "live room," a room with highly reflective walls. In other words, it was an extremely bright room. The room was about 25 feet long, 20 feet wide, and 20 feet high. A short burst of sound is introduced into the room, and it echoes around for a long time. Then a piece of some material, say acouctical tile or a seat cushion about 10 x 10 inches in placed on one wall. The sound is repeated, and from measurements of the decay, it is possible to accurately measure the absorption coefficient of sound by the material as a function of frequency to very high accuracy. Yet it is far beyond the ability of human hearing to even be able to detect whether that piece of material is there or not in the test.You can't hear sound at 10 Hz or 50 Khz, but lab equipment can. You cannot detect which signal is louder if they differ by 0.01 dB, but lab equipment easily can, You could not detect if a notch 5 Hz wide and 0.1 dB deep centered at 1000 Hz was cut out of a speaker's response, but that would be simple to measure in a lab. The list goes on and on.
The sensitivity of lab measuring equipment is so far beyond what your ears can hear that you might not even believe it if if you saw it demonstrated.
Follow Ups:
and understanding how it correlates to how / what we hear, AND also to other simultaneous auditory stimuli is the real trick. I really don't know of anyone that listens to individual test tones, standardized test signals or noise bursts on a regular basis. Hence, drawing conclusions from such test methodology can be troublesome and deceiving at best.Music is very complex in nature, presenting non-symmetrical signals of various amplitudes and frequencies simultaneously. There's so much going on at one time, taking accurate measurements and being able to extrapolate usable data corresponding to how the human ear / brain processes that info is "less than optimum" at this time.
While we have some phenomenally advanced test equipment available to us, interpreting the test results and being able to interpret / apply what we learn from such is still not perfected. Besides all of that, we still have to factor in differences in individual hearing capabilities, varying levels of listening skill and personal auditory bias.
Science is a great and marvelous thing, but only when applied in a meaningful manner. Otherwise, "facts" aren't really universal facts, they are responses and results achieved under specific test conditions. Whether or not those specific test conditions apply to reality may be something all together different. Sean
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Sean:Yes indeed. We're using science to render art.
At some point, we must put away the measuring equipment, "render the art", and use a completely different set of 'test criterion', which is human perception.
Not to say that measurements are invalidated (although in some extreme cases we see this very thing), but it's when we start to attempt to lay down some sort of corolary between what a good measurement is and what a good sound is - that's where there is much disagreement.
I believe you can't really argue with ruler flat amplitude response. And some maintain that you need to go one step further and have flat frequency response which is technically a representation of amplitude AND phase response. (They use the term frequency response instead of amplitude response... but it's really not 100% accurate.)
Where you DO get into interesting subject area is when you start talking about spacial cues, and the types of delays and other sonic artifacts that our ear-brain hearing system is very good at processing. I've never heard any say that they measured the system, and can quantify that the soundstage is "correct". Have you?
I think (and this is just my humble opinion) that we need to use the measurement gear to measure what it measures well, and the ears to "measure" what the ears measure well. In my example, I was showing how the ear really sucks as a tool for measuring frequency response. F/R was not really a useful function for primal man. Locating the source of sound is VERY useful - life and death really when you're a primate walking among dangerous creatures of all shapes and sizes.The quest for this corollary between what we can measure and what we can hear is the source of much debate. Many say our ears are much more sensitive transducers than measuring equipment we have. This I doubt. What I think the problem is? We're not measuring the right things if we want to try and and actually quantify what constitues a "correct" soundstage (for example).
So I do find it funny that I am considered to be a staunch objectivist simply because I try and make a correlation between measurements and what I hear. (Heck most times I am busy just trying to INTERPRET measurements themselves and ensure that they are even useful or the result of an accepted (or desired) test method).
In the end, since we're rendering art for the purpose of enjoying art, at some point you have to include LISTENING, PERCEIVING and JUDGING the art (as rendered) and describe it with the terms that are valid for our hearing system.
+0.24 db at 4132 Hz, Q = 3.2 ??? No.
Sweeter, nicer, warmer, smoother, palpable, engaging, fast, slow, bloated, thin, deep, wide, 2D, 3D, black, bright, sharp, soft...
These are the QUALITIES we can "Measure" (perceive) with our ears!
My formula for totaly awesome sound?
Good measured quantities + good perceived qualities = GOOD SOUND
The only time I get hot around the collar is when folks confuse quantity with quality and start trying to QUANTIFY what something is doing or how it works simply by listening to it. You can't explain nuclear fission by looking at the sun. And you can't explain *all* acoustical phenomenon by simply listening to music.
Anyways, sorry for giving you a hard time the other day. I was being devil's advocate and a RPITA (royal pain in...) I have a lot to learn about transmission line theory.
Back to the books...
No problem. We are probably much closer to being on the same page than it might appear from this thread. Best wishes to you and good listening. Sean
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