Excuse me, what are you trying to measure? Loudness?
The basic problem in using these kind of temporal windows is the output depends on the input signal characteristics like duration. The question rises: What is the 'right' test signal ? Sinusoid, noise, clicks ???
If you have invented a model of loudness, it will give you results depending what you feed in. How to use it in loudspeaker design? Let's say we want to determine optimal frequency response using our loudness model and at first we use short burst to tune the freq response, next we use longer tones and only find out that the frequency response we just polished is totally twisted ! Did we gain anything by doing this? Except proving that human perception depends on the signal characteristics
About the specific time windows, Zwicker states, for example, at 2kHz the loudness is determined during up to 100ms (if the signal duration is at least 100ms) so your "couple of ms" may be good for something but not neccessarely for loudness.
Zwicker Psychoacoustics Facts and Models book have some information. Try to find it maybe.
Not only 'tone duration' affects loudness, but also frequency content, temporal characteristics like modulation, and more complex matters like masking. Not a simple issue.
- Elias
![appl[1].gif](https://www.yesfans.com/images/smilies/appl[1].gif)
He he.. Stereo imaging falls apart !
For some it falls apart already at much lower freqs, like 3kHz, and for some even at 1.5kHz. (See this thread !)- Elias
Equally challenging it is to try to figure how a signal measured with omni mic will be perceived by human auditory system !!!
Better to at least try to do it right. Using omni mic does everything wrong from the beginning.
- Elias
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I got incredibly good results using two electret Radio Shack 1/2 inch omni mics (aimed forward) on either side of an 8 inch round flower pot (as a head). Some more "professional" head mics seem to have a rolloff in the treble when the subject being recorded is right in the middle. I'm not sure what is best. How do you think it should be done?
The Salmi paper uses an exponential decay window (or at least a 4 step analog approximation to one). He argues that window time should be proportional to critical bandwidth and so has a window length proportional to frequency above 500 Hz and of fixed length below 500 Hz. I've got the paper at work and may attach some figures from it tomorrow. Salmi admits the particular numbers of his model are approximate.
The Kates model is more sophisticated and comes straight from hearing and brain response, although the end result is similar.
I'm not too bothered about the exact time window length. Both Kates and Salmi show loudspeaker in room curves that are similar: essentially the anechoic response for the top decade, the steady state response for the bottom decade and a window that clearly shows floor bounce and back wall or side wall for the middle decade. This agrees with Bech's studies so it all comes together nicely.
Kind of a unified field theory for loudspeakers.
David S.
Yet your before and after measurements below show large changes in the midrange and treble balance ?
Thanks for making my point for me
This is another reason why steady-state room measurements are so bogus at high frequencies, especially treble. Not only do they not directly map to the on-axis response of an arbitrary speaker, they change dramatically with just a few inches of microphone movement, one reason why Auto-EQ measurements tend to be so hit and miss - put the microphone in a slightly different place, get a different EQ result!
To get repeatable results you need to measure in a way that is repeatable, and apart from the whole on-axis vs power response issue, steady-state results never are repeatable within a room because the tiniest microphone or room object movement changes the results unpredictably.
Windowed measurements though are extremely reliable. I've taken 1 metre measurements of my speakers in-situ before, (only accurate down to about 1Khz due to side-wall reflections) then come back days later using only a measuring tape to get the distance from microphone to floor and front panel the same, only judged that the microphone is square onto the speaker by eye, and got measurement results that track from 1Khz to over 15Khz so closely that the lines actually perfectly overlay in overlay mode. (Tiny fraction of a dB)
The reality is I could be out a couple of inches or more and it would still be within a fraction of a dB, and any change would be an actual change in the response of the speaker in that point in space rather than room effects.
If I were to do that with a steady-state response (even at that close distance, let alone further back) I know that I'd never get the same measurement result twice once the microphone had been moved, even if I attempted to measure its position. (Been there, done that...)
It's hard to judge on a steady-state measurement, but the above change seems to have made the bass response better and everything else worse. How does it sound ?
What I'd really rather see is a 1 metre on axis reflection free windowed measurement taken before and after the Auto-EQ system has done its thing to see whether it's making the on-axis response better or worse in the midrange and treble. My guess looking at the above is that it is making it worse.
But is that change audible ? Or is it an example of the steady-state response being altered by room object changes at frequencies where the direct response dominates our perception ? How did it sound ?
Multiple microphone stands ?
You can definitely hear the bass/midbass changes though the foam coffee table isn't as audible as it looks on the graph. Can't really say the treble changes.
I'm going to try that close measurement(s) next time I make some graphs. That's a good idea. Speakers w/o power response issues shouldn't change of the program is well written and universally good.
Don't worry about me putting stock on the treble side--you know I mentioned I don't first off. The bass side, every position looks similar with all the treatments up. Not exactly of course, but not too bad and much better than without.
Dan
A sidestep now as the matter was in the focus earlier,
but a nice reading i think:
"50 Years of Control Room Design"
by Jan Voetmann
"It should be recalled that the function of the control room is twofold, which is often
overlooked:
On one hand the control room is the “tool” that – together with the monitor loud-speakers or
vice versa – should illustrate or auralize the sound engineer’s (and producer’s) efforts in the
creative process of the new recording or music production. This process encompasses putting
tracks together, adding sound effects, balancing the mix, creating “space” around the
instruments and the vocal, etc.
On the other hand, the control room should also mimic the acoustics of an average living
room when checking of the final result of the recording, simply because most musical
productions, whether on CD or in broadcasting, are aimed at the listening environment of a
living room. For the same reason a number of investigations has been dealing with the
acoustics of the living room.
This paper attempts to give an overview of sound control room design over the last 50 years ..."
http://www.akustikjav.dk/assets/PDF/50-years-of-control-room-design.pdf
but a nice reading i think:
"50 Years of Control Room Design"
by Jan Voetmann
"It should be recalled that the function of the control room is twofold, which is often
overlooked:
On one hand the control room is the “tool” that – together with the monitor loud-speakers or
vice versa – should illustrate or auralize the sound engineer’s (and producer’s) efforts in the
creative process of the new recording or music production. This process encompasses putting
tracks together, adding sound effects, balancing the mix, creating “space” around the
instruments and the vocal, etc.
On the other hand, the control room should also mimic the acoustics of an average living
room when checking of the final result of the recording, simply because most musical
productions, whether on CD or in broadcasting, are aimed at the listening environment of a
living room. For the same reason a number of investigations has been dealing with the
acoustics of the living room.
This paper attempts to give an overview of sound control room design over the last 50 years ..."
http://www.akustikjav.dk/assets/PDF/50-years-of-control-room-design.pdf
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I believe that these days popular music is mixed for automobiles and headphones since people don;t listen in living rooms anymore.
Exactly. And a mix having a dynamic range larger than 6 dB would drown the quiet parts in background noise -> no quiet parts -> no dynamics -> loudness war.
Well, Dr. Geddes thank you for disillusioning ...
when embedded in the "matrix" completely we won't even need
headphones anymore.
But i guess for recordings in the classical and jazz genres e.g.,
the "living room paradigm" may still hold, as well as for many
recordings in popular music. Surely there are genres which may
have a different focus.
But please see below (last picture on that page) Joachim Kiesler
head of ME Geithain, an acknowledged monitor speaker company
in my home country, with "currently preferred program material"
on his desk ...
Firmen-Bericht Reportage Musikelektronic ME Geithain Interview
when embedded in the "matrix" completely we won't even need
headphones anymore.
But i guess for recordings in the classical and jazz genres e.g.,
the "living room paradigm" may still hold, as well as for many
recordings in popular music. Surely there are genres which may
have a different focus.
But please see below (last picture on that page) Joachim Kiesler
head of ME Geithain, an acknowledged monitor speaker company
in my home country, with "currently preferred program material"
on his desk ...
Firmen-Bericht Reportage Musikelektronic ME Geithain Interview
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Don't get too depressed - some people still do magnificent recordings, they do exist. And some in the past are outstanding as well. But there is no doubt that the "popular" segment is after something which is not compatible with a high quality system.
I actually love a lot of my teenage son's music. Some of the artists are very innovative and musical (some are idiots who must be deef, nothing new there). But their recordings are unlistenable on my "audiophile" system because they are so badly done. And yet, somehow, they sound fine in the car, which is the only place that I will listen to this stuff. They sound bad on good headphones, but typical on bad headphones. There is a shift in taste, make no mistake about it, but will all other music be "absorbed" into this problem. I don't think so.
I had almost given up on going to live performances anymore because the sound was always so bad that it wasn't worth it. Then I saw Allison Krause last week and I learned that all is not lost. There are some engineers out there who are capable of doing great live sound.
I actually love a lot of my teenage son's music. Some of the artists are very innovative and musical (some are idiots who must be deef, nothing new there). But their recordings are unlistenable on my "audiophile" system because they are so badly done. And yet, somehow, they sound fine in the car, which is the only place that I will listen to this stuff. They sound bad on good headphones, but typical on bad headphones. There is a shift in taste, make no mistake about it, but will all other music be "absorbed" into this problem. I don't think so.
I had almost given up on going to live performances anymore because the sound was always so bad that it wasn't worth it. Then I saw Allison Krause last week and I learned that all is not lost. There are some engineers out there who are capable of doing great live sound.
You're exactly right, although I think all is not lost. After nearly 20 years of the loudness cold war, the practical limits of compression and limiting have long since been reached, and there are some early signs of a backlash against heavy compression that may snowball into a full fledged retreat from ultra-compression over the next 5-10 years. One can only hope. Certainly some of the indy and unsigned, direct-to-internet musicians are heading in this direction.
Its an interesting problem, I've long been aware of the fact that as your playback system gets better and better, particularly speakers and room set-up, good recordings sound better and better, while bad recordings often sound worse and worse, to the point where they become un-listenable.
I have music that I like on ear phones or in a car, but I can't listen to it on my main system because all I can hear is the flaws in the recording. Quite how a "bad" system can make a bad recording seem more tolerable I can't work out, you would think that bad recording + bad playback system would sound cumulatively worse.
Perhaps when we hear a system that is uniformly bad, such as a poor car system which is full of resonances, non-flat response, high distortion and so on, our brain adjusts its expectation level, as everything we play sounds bad since the faults of the system dwarf the faults of the bad recordings. Everything sounds much the same (bad) so we just tolerate it.
Listen to the same bad and good recordings on a high quality system and the difference is quite jarring.
In the context of this thread I've also noticed that a low direct/reflected ratio tends to have the same effect, and can disguise certain flaws in bad recordings making them seem a little bit more palatable, whilst a high direct/reflected ratio is more "revealing", making good recordings sound better, but bad ones worse.
Perhaps one reason why some people prefer wide dispersion speakers - it might not reach the same heights of definition and be quite as revealing on the excellent recordings, but it can be a lot easier to stomach on the bad stuff.
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There seems to be some agreement and maybe this is really the crucial point:
You should buy better ear phones
good earphones offer transparency and neutrality that no loudspeakers can achieve, regardless of price
not agreed
I just spent a few days on the web hunting for free binaural recordings. I wanted to put my fancy speakers with their inter-aural cancellation to the test a bit more. I was humored by the range of quality in the recordings. About a dozen are pretty darn good, and worked well on my system. They of coarse all work better with headphones. Another 2-3 dozen are pretty bad, apparently done my amateurs. How something is recorded is just as important and complex as how they are played back.
One thing I noticed is that audio signal processors have gotten pretty darn good at creating synthetic binaural imaging (I don't know what brands or models). They've replaced the pan pot with one that includes consistent timing cue info in the lower midrange, and the sense of envelopment and sounds traveling around my room is very impressive. They may be employing some other psycho-acoustic tricks as well. Some people seem to think high end audio is dying. I don't see it that way at all. We may not be real good at re-creating exactly what an audio event was like in person, in our listening rooms, but we are getting real good at making a very enjoyable audio experience in spite of it all. Well, sometimes anyway.
One thing I noticed is that audio signal processors have gotten pretty darn good at creating synthetic binaural imaging (I don't know what brands or models). They've replaced the pan pot with one that includes consistent timing cue info in the lower midrange, and the sense of envelopment and sounds traveling around my room is very impressive. They may be employing some other psycho-acoustic tricks as well. Some people seem to think high end audio is dying. I don't see it that way at all. We may not be real good at re-creating exactly what an audio event was like in person, in our listening rooms, but we are getting real good at making a very enjoyable audio experience in spite of it all. Well, sometimes anyway.
As a musician myself, I have to admit that it's more about what the music is, than the quality of the recording. Since I'm not afraid of things like "tone controls", I can make pretty much any recording listenable. Some of the highest fidelity recordings I've ever heard are actually really boring music, with little or no soul. Most of my highest fidelity CD's have one good song, and the rest is crap.
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