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Old 17th August 2012, 12:34 PM   #26551
DF96 is offline DF96  England
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Quote:
Originally Posted by RNMarsh
And, FFT does it for most everyone in science.
FFT does what for most everyone in science? It tells us what frequency components are present. You are beginning to sound like those who accuse others of 'believing in' THD.

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Originally Posted by john curl
DF96, what is a 'lay listener' vs an 'expert or professional' listener?
Ask Richard Marsh, for it was he who first used the term. In the context he may mean someone who recognises good sound when they hear it, but doesn't know enough maths or science to properly understand the circuits producing that sound.

Last edited by DF96; 17th August 2012 at 12:37 PM. Reason: extend
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Old 17th August 2012, 12:42 PM   #26552
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Can any of these do a 20 second transform so we can see what energy is present in real music?
Almost any microphone will have noise increasing at low frequencies. A fun experiment you might want to try is to put a horn on to a GE Novasensor pressure guage. The lowest range one is not too sensitive (15uV/Pa) but it does go to DC. You will find that barometric pressure has a 1/f spectrum like most things and eventually will swamp out the music.

I might ask why is this relevant?
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Old 17th August 2012, 12:58 PM   #26553
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Ah, DF96, describing engineer Ed Simon as a 'lay listener' was more an implied insult, than anything accurately describing Simon, himself.
For the record, I strongly depend on 'lay listeners' to give me the feedback necessary to make better audio electronics. In fact, pleasing these 'lay listeners' is what I do, both as a personal interest, as well as to earn an income. May there always be happy 'lay listeners'.
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Old 17th August 2012, 02:32 PM   #26554
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SY & Scott

I had wanted to avoid sampling theory but it has clearly raised its head.

If it takes a "Golden Ears" multiple hours of listening to "hear" these "Differences" then what data would we have to capture of real music to do a Fourier analysis of it.

To be as accurate as possible since there are music components to 100 khz we should look that high. We really can't set the whole record length as a few hours but let's cheat and do 10 second samples.

So that would give us 1,000,000 points for a transform. If we use FFT we need n log (n) operations so that would be 6,000,000. We would want 200,000 samples (or more) per second for 60 seconds per minute and 60 minutes for one hour. That would be 4.32e15 operations.

Now how many instructions will it take per operation?

In 76-77 I built my own Fourier based analyzer as I could not afford a commercial unit. Even 1/3 octave analyzers were a bit steep. But someone may have the ability to do it in fewer instructions than I used so let them answer.

I later built a room simulator based on the TRW multiplier accumulator chip when that became available. It was a fun and insightful toy.

Of course if we want to capture music including direction we will need six channels for mono. With the bandwidth limits of microphones we just might need to use three different types so bring the final count up to 36 channels!

Now amazingly enough there are computers large enough top process this transform! (But then how do you analyze all of it?)

DF

The issue is that you have a definition of distortion that is limited. If you feel better about yourself by denigrating others, so be it.

Scott,

Yes noise increase as the frequency goes down not just for microphones, but for air motion etc. The classic tale is of the folks who built mic preamps that were RF condensor based and good to DC. Their recording meters were always clipping from stuff they often couldn't hear. One time they really went crazy and a bit later they understood why when the thunderstorm got close enough for them to hear the lightning strikes.

I have had to measure the noise impact of steel wheels on steel tracks. The flat spots from braking create giant levels of LF energy. Some of which is perceived by other than one's ears.
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Old 17th August 2012, 02:42 PM   #26555
SY is offline SY  United States
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Originally Posted by simon7000 View Post

If it takes a "Golden Ears" multiple hours of listening to "hear" these "Differences" then what data would we have to capture of real music to do a Fourier analysis of it.
Sociology is not amenable to computer analysis.
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Old 17th August 2012, 02:46 PM   #26556
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SY & Scott

So that would give us 1,000,000 points for a transform. If we use FFT we need n log (n) operations so that would be 6,000,000. We would want 200,000 samples (or more) per second for 60 seconds per minute and 60 minutes for one hour. That would be 4.32e15 operations.
Ed, I already told you student Matlab on my PC does a 4 million point double precision FFT in a few seconds. This is all beside the point no one claimed music or noise is periodic you did.

Take another signal processing example. Take the impulse response of an RIAA filter (out as far as you want, < 24bit LSB?), then convolve that with your signal to apply the RIAA filter. This process is enormously speeded up by using overlapped FFT techniques (convolution is simply multiplication in the conjugate domian). The answer can be proven EXACTLY the same, no "infinities" required.
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Old 17th August 2012, 02:48 PM   #26557
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This is all beside the point no one claimed music or noise is periodic you did.
Opposite, Ed claims that you can't formally treat an acquisition of music or noise as periodic. We've now apparently moved the goalposts, minimally miked "purist" recordings don't count, and you have to look at an hour.
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Old 17th August 2012, 02:55 PM   #26558
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Originally Posted by scott wurcer View Post
little has been done to confirm what is heard or not heard.
Yes, many new tests should be done, for the reason that much of "confirmed" was done 50 and more years ago on a bearded equipment.
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Old 17th August 2012, 03:07 PM   #26559
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Opposite, Ed claims that you can't formally treat an acquisition of music or noise as periodic. We've now apparently moved the goalposts, minimally miked "purist" recordings don't count, and you have to look at an hour.
I meant to say he said we did, but I'm losing the point of attacking FFT's in the first place.
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Old 17th August 2012, 03:29 PM   #26560
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I meant to say he said we did, but I'm losing the point of attacking FFT's in the first place.
It's the new meme. Get with it, Gramps. You'll see it next week in Urban Dictionary.
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