What's More Accurate a Microphone or Human Hearing?

Phase 2

Phase 2

Audioholic Chief
According to the female race humans, Nothing can compared to the hearing of a female human. From what I have witnessed they even can see and hear through walls. Their memory is so accurate on what they hear and see it even boggled the mind of Einstein. (Joke),. good article.
 
Matthew J Poes

Matthew J Poes

Audioholic Chief
Staff member
According to the female race humans, Nothing can compared to the hearing of a female human. From what I have witnessed they even can see and hear through walls. Their memory is so accurate on what they hear and see it even boggled the mind of Einstein. (Joke),. good article.
I didn't realize Females were a unique race of human, but I appreciate the sentiment. Thanks. I generally try to avoid arguing with my wife. I'm usually wrong anyway.
 
Phase 2

Phase 2

Audioholic Chief
I didn't realize Females were a unique race of human, but I appreciate the sentiment. Thanks. I generally try to avoid arguing with my wife. I'm usually wrong anyway.
They a very subjective part of the human race. I do believe and I can be wrong, No man has ever won a argument with a wife, especially. Females are special that I'm sure of. Again good article.
 
Matthew J Poes

Matthew J Poes

Audioholic Chief
Staff member
They a very subjective part of the human race. I do believe and I can be wrong, No man has ever won a argument with a wife, especially. Females are special that I'm sure of. Again good article.
Thanks!
 
E

<eargiant

Senior Audioholic
View attachment 27527

We commonly debate on these forums objectivity vs subjectivity, measurements vs what we hear. The problem is complex and trying to understand the truth that underlies this question can be difficult. Is a mic more accurate than human hearing?

Most would say “Of Course!” and yet we need to pause and think, is this even the right question to be asking? A microphone and our ears are not the same thing and a room measurement cannot be interchanged with our hearing, which forces a needed pause as we think about this question. Accurate in what way? If our goal is a system that accurately reproduces the real event, and I would contend that is our goal, then we must look to psychoacoustics to understand the relationship between measurements and our hearing perception. Measurements are of no value without knowledge of how they correlate with what we actually hear, what we need to look for, what matters. In the end, I think the most important thing remains our enjoyment, but it is none the less fun to learn about how measurements do correlate with what we hear. What matters, what doesn’t, and the flaws with traditional measurement practices. This article focuses on how our hearing works, how sophisticated it is, and compares/contrasts that with how measurements in a room work. It then provides some nice examples of how well our hearing can pick up the sound of a room or acoustic flaws, that really can be difficult to detect in measurements.

If it can't be measured is it really there? I here this a lot. My response is, just because you can't measure it doesn't mean it can't be measured and doesn't mean it isn't there. Once you begin to understand how measurements taken in a room work, it's easy to see why they can't detect certain flaws that really are there. My favorite part of writing this article was getting feedback from Floyd Toole in which he stated that these types of in-room measurements are dumb (as in lacking sophistication). A bold statement I never would say on my own, but Toole, he has earned the right to say that, and he is right.

When Gene read the article he pulled out these two points:
  • the only flutter echo that matters is one caused by your speakers in their final location that is audible at your listening position.
  • measurement equipment is typically omnidirectional and monophonic, our ears are directional and binaural.
I think these are actually two of the more critical points made in the article because they address common misconceptions that are repeated over and over. Sometimes we simplify the situation so much we lose sight of what is really going on.

I hope you enjoy this article and that this sparks some thoughts and lively debate. We at Audioholics enjoyed writing the article as it gave us a chance to share some thoughts on this issue and elaborate in far greater detail than forums typically allow. Our hearing is complex and sophisticated. It is capable of miraculous things and yet is commonly dismissed as flawed and untrustworthy. Yes, our hearing can be tricked, we can be tricked, but then, the same is true of these measurements (as you will see in the article). Please read the article and come back here to share your thoughts. Do you agree? Disagree? Did this make you think differently? Let us know.

READ: What's More Accurate a Microphone or our Ears?
Great article- very refreshing to see here on AH.

I've brought up similar points in the past here about evolution/hearing/spatial, etc. and have also asked which measurement will gauge the soundstage width and depth capabilities of a speaker. I was roasted by the true (speaker measurement) believers so I'm not surprised that you're getting some push back.

There's a lot more to the reproduction capabilities of a speaker than what a high quality mic and a few static (often room dependent) measurements can ever convey.
 
Matthew J Poes

Matthew J Poes

Audioholic Chief
Staff member
Great article- very refreshing to see here on AH.

I've brought up similar points in the past here about evolution/hearing/spatial, etc. and have also asked which measurement will gauge the soundstage width and depth capabilities of a speaker. I was roasted by the true (speaker measurement) believers so I'm not surprised that you're getting some push back.

There's a lot more to the reproduction capabilities of a speaker than what a high quality mic and a few static (often room dependent) measurements can ever convey.
Thanks!

When I have some time to pull up the relevant quotes from Tooles book as well as the research he cited I will try to explain more of what this is all getting at. It isn’t that research hasn’t allowed us to come up with a set of measurements that can do a good job of telling us if a speaker will sound good or not. The models to date are really pretty good. It’s that this research doesn’t apply to in-room measurements taken the way most people would. They apply to specific free-space measurements. Toole cites research that actually points out that while in-room measurements can tell us if a speaker is bad, they can’t similarly tell us if a speaker is good. Where as anechoic measurements can tell us both.

None of these measurements and none of Tooles work delves deeply into how measurements correlate with our perceptions of a better soundstage. He certainly talks about it, but my impression is that it’s a mixture of a hole in the research and more room/setup dependent. @shadyJ and I have been discussing our own hypothesis quite a bit.

Here is my hypothesis, one that hasn’t been studied explicitly with sufficient rigor, but has some supporting evidence in the literature. I believe that the primary attribute of a speakers imaging comes first from how well matched each speaker is. Any differences in the pair would mess up the imaging, so speakers worth poor tolerances might image bad. I suspect this is a non-issue for the most part today. Second, I believe that an interaction between speaker directivity and the room dictates the quality of the imaging. I believe that when there is more direct sound and less early reflections the imaging is perceived as being more precise. That when there are more early reflections and less direct sound, the imaging is less precise and more diffused. A quality some may like since it’s been noted that we often can’t precisely place instruments on a stage in a live venue.

I believe that speakers with narrower directivity will generally be perceived as having a more precise soundstage. As such panel, electrostatic, and controlled directivity speakers may be perceived as having the most precise soundstage but also one that tends to stick between the speakers. Wider dispersion speakers may be a bit more diffuse but may also appear to come from a larger stage. However I think that adding early reflection absorbers could then lead to a wide dispersion speaker having a precise stage as well for the same reason.

I had some past theories on possible measures of soundstage using binaural impulse response. You could track an object using this method but it turned out that I couldn’t do what I wanted with the reflections in the measurement. I could tell their direction in the azimuth generally and that was it. I think that 3D IR measurements and special binaural test recordings are necessary to develop an objective measure of soundstage accuracy. Further, I suspect this isn’t a lab measurement, it’s room dependent, and as such, has little likelihood of seeing the light of day. It seems most research that would need this has long since moved onto multichannel 3D sound.
 
Matthew J Poes

Matthew J Poes

Audioholic Chief
Staff member
I said I would post this when I get a chance, so here we go:

On page 452 of "Loudspeakers and Rooms for Sound Reproduction: A Scientific Review" published by Floyd Toole in 2006, we find a great review of the early research into measurements of speakers in-room and how this was correlated with perceived sound quality. Remember that the premise of my paper was not to be damning of measurements (which I stated) but to note that in-room measurements are a poor indicator of sound quality.

First Toole notes a BBC finding that "we measure differences that we seem not to hear" which is an important statement around the relationship between in-room measurements and sound quality. As noted previously, in-room measurements contain a lot of information that our ears can filter, but the measurements cannot without losing too much resolution and becoming hopelessly uninterpretable (To remove all room reflections including very early reflections would require an exceedingly small window causing the measurement frequency resolution to only be accurate at exceptionally high frequencies).

He goes on to say:
"These observations imply that some of the problem lies
in our interpretations of measurements made in small
rooms. The horrendously irregular steady-state
“room curves” that we see simply do not correspond to what we
hear. Did our problems begin when we started to make
measurements? Are we incapable of hearing these things?
Or is it that we hear them, but they simply become part of
the acoustical context within which other acoustical events
occur, and we have some ability to separate the two? The
answer turns out to be some of each."

This is basically stating what I said in the article, that the measurements contain a great deal if information that do not seem to correlate with what we perceive as good sound. They often look horrendous but don't sound it. This is totally unrelated to the notion that a flat anechoic response is the biggest predictor of sound quality. Flat anechoic responses do not necessarily translate to a flat in-room response, though certainly, a flat anechoic response does guarantee a better likelihood of a good in-room response (it will always be less flat and smooth than the anechoic, reflections do that).

But I also made a point that prior research had suggested that the in-room response, absent knowledge of the anechoic response, is not a good predictor of sound quality. That while an obviously poor in-room response is likely a guarantee that the anechoic response is poor, the oppossite is not true. A flat in-room response is not a guarantee of good sound or a flat anechoic response (since we can artificially create that flat in-room response, and further, that a speaker can measure flat anechoically at the listening axis but not the first reflection axis).

In defense for the need of good psychoacoustic research, Toole notes:
"The performance of a loudspeaker is much more
complex than anything revealed in an on-axis anechoic
measurement. The perceptual processes of two ears and a
brain are vastly more complex than anything revealed in a
room curve or a reverberation time".

This in many ways was the point of my article. Not that measurements can't tell us a lot about good sound, but that measurements in the absence of this science is not valuable, and that this science has been done, to a point at least. This science showed that in-room measurements are a poor indicator of sound quality, but specific anechoic ones tell us at least most of what we perceive as good sound. I still find, from time to time, speakers that suggest that this science may be incomplete, and when you scour the many forum and blog posts by folks like Toole and Olive, you find often where they indicate that perhaps there is more too it. For example, could speaker directivity actually play a big role in sound quality? Most of the work published by Toole and Olive suggested that the ideal response was flat on the listening axis but had a downward tilt to the early reflection axis, and further, a steep downward tilt to the power response. That this correlated highest with good sound. Here's the thing, it is likely that Toole and Olive never measured a speaker that met the smoothness/flatness priority across all angles, but actually had very wide dispersion (a speaker meeting the above criteria must be somewhat directional). What if a speaker's forward radiation is smooth, flat, and uniform out to an unusually wide angle? In such a scenario, the in-room response would be flat, not downwardly tilted (Because the combined total energy wouldn't be stronger at LF's, it would remain flat). Exceedingly few speakers meet this criteria, I know of only two, and I am confident that Harman has never tested either in their labs.

Ok back to Toole's notes: On page 467, figure 17, he shows that the in-room response is best predicted by some combination of the early reflected sound and power response. The in-room measurement looks most like the early reflected sound, though the HF's clearly roll-off more like the power response. This is likely due to the fact that most small rooms actually have quite a bit of HF absorption, including the air itself. This is why I noted above that the in-room response of a speaker whose listening axis and early reflected sound response are flat would thus have a flat in-room response.

On page 472, Toole notes that above the transition frequency (in what is known as the Stochastic zone) the sound of the speaker and room are intertwined and inseparable. Equalization of this based on in-room measurements would risk applying the wrong correction to the problem. Namely, we can't know if the problem is speaker setup, room acoustics, or speaker problem, and the fix to any of these three is different. Auto-EQ can't tell either, so there lies a risk in using a room EQ system that is automated and unable to know. The best fix for people wanting to use proper forms of Room EQ are to only use speakers which meet the qualities of a flat and smooth anechoic response on the listening axis and an early reflection and power response which remain flat, but having lower output in the midrange and treble. In this scenario, Room EQ should not have any issues, but then again, it also may not provide any benefit.

I want to highlight a specific claim he makes, however, one that I've been echoing here and that I think is quite important to this discussion:

"Comprehensive high-resolution anechoic frequency-
response data on loudspeakers contain sufficient infor-
mation to permit remarkably good predictions of sub-
jective preference ratings based on listening in a normal
room. Single measures, such as the on-axis frequency
response, sound-power response or steady-state in-room
curves are less reliable."

He states that, based on the research he has conducted in the past, and the research of others, they have found that the reliance on in-room steady state measurements (that is the frequency response measurements we typically use) is an unreliable predictor of good sound.

Moving onto why Toole states this (beyond his own work) is older work which Toole cites in a prior paper. "Loudspeaker Measurements and their Relatonship to Listener Preferences: Part 1" 1986 AES, lays out a history of how we got to where we are today. It notes that early research into which meausrements correlate best with perceptions of sound quality suggested that the power response may be a good indicator. However, that some researchers found that it was possible to be fooled, in that "a non-smooth power response measured in the reverberation room indicates a similarly irregular frequency response as measured in the anechoic chamber. While it cannot be stated that a speaker system that shows a smooth response in the reverberation room will necessarily sound good or have a smooth pressure response, the reverse is true" (Brociner and Von Recklinghausen) found on page 229.

That is, a speaker that measures poorly in a normal small room will likely measure poorly in an anechoic chamber. A speaker that measures well in a normal small room will not necessarily sound good or measure well in an anechoic chamber. So we can't use in-room measurements, in isolation, as any indicator of good sound.

See https://pdfs.semanticscholar.org/7b0e/3101e1788608d75d024ac926d25a077b85bc.pdf
and
http://www.mariobon.com/Articoli_storici_AES/Toole/AES_1986_Toole_01.pdf
 
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