[johncarm]

My mistake: when he quotes me and then mentions "phase distortion" in his response to me, I just assumed he was answering me. To avoid confusion, he should quote the person he's responding to, not me. I think perhaps you are confused about the word "answering".

I don't think the definition of "random" is relevant in this thread, but I strongly doubt your definition is different than mine. Or perhaps you are confused? Does it matter here anyway? Get a dictionary, and I stand by everything I wrote.

As a practical matter, we might want to use a white noise source to measure the transfer function of a device. A truly random white noise source shares a lot of properties with a constructed finite length signal of exactly flat power distribution via pseudorandom phase. If we look at the practical reality, there's not as much argument over the definition of "random" and your constructed signal has good uses.

 

[SoundAndMotion]

Oh my.

LOL

Would you be honest enough to reveal any truth to my claims?

I'll always only answer honestly, but if I don't want to answer, I won't.... meaning I won't lie. In the case of your post, I'll answer everything.

Are you some sort of perception expert?  

"Expert" is a funny term and kind of throwing me, but perception research is my field.

A professor, or maybe just a leader in some circle or group with a fundamental interest in perception?  

You sound as though you think I'm leading a perception cult. I'm not a professor, but I taught grad courses ending about 10 years ago. I was a "group leader", but that sounds more impressive that it was. I led a small group of grad students, but that ended about 5 years ago. I now work for for an SME, but I lead no one; I'm kind of off on my own-the only one doing research here.

I only ask, because there have been nearly a half-dozen similar threads all eventually coming around to some issue about perception with audio.  If I had to guess, it would appear that there is some perverse curriculum in a school course to invade this particular forum to argue this topic.  It almost always begins in a similar way, and migrates to audio perception.

Perception doesn't belong here? It's a perverse curriculum? Sorry, but I admit that I think understanding perception is relevant to understanding the science of head-fi. I'm curious why you would disagree, but given how central the topic of perception is to so many posts here, I don't get your perspective.

You sweep into every single one of these discussions as the master that has to control the situation that your disciple has gotten themselves into.

I don't post too often, but when I do, I'm sweeping in? Hmmm. I have no disciples here. No one here knows me (and I don't know them). One person who doesn't post here anymore knows my first name, but not my last.

So no big conspiracy to take over the forum. Either amusing or scary that you think so.

Cheers.

 

[sonitus mirus]

 

 
Thanks, I'll certainly sleep better now.  
 
To me, auditory perception is an integral part of hearing.  I would say it belongs here.  There is no disagreement from me on this issue.  

 

[jcx]

I don't know if this might help johncarm www.davidgriesinger.com/intermod.ppt
 
hmm linking weird/broken, but the top level is a great plce to start anyway
 
Slides from the AES convention in Banff on intermodulation distortion in loudspeakers and its relationship to "high definition" audio.

 

[reginalb]

My mistake: when he quotes me and then mentions "phase distortion" in his response to me, I just assumed he was answering me. To avoid confusion, he should quote the person he's responding to, not me. I think perhaps you are confused about the word "answering".

I don't think the definition of "random" is relevant in this thread, but I strongly doubt your definition is different than mine. Or perhaps you are confused? Does it matter here anyway? Get a dictionary, and I stand by everything I wrote.

 
You're arguing about white noise. Coming up with a way to construct white noise, right? That's your argument with Joe. Here is the definition of white noise that you provided:
 

...the Wikipedia article on white noise is pretty clear for me. First sentence:
"In signal processing, white noise is a random signal with a constant power spectral density."

 
The definition of random is quite important to the discussion. 

 

[SoundAndMotion]

You're arguing about white noise. Coming up with a way to construct white noise, right? That's your argument with Joe.

Read the whole thread! I argued that phase is a necessary part of the frequency domain description of a signal. My example: a theoretical impulse and theoretical (newly added adjective) white noise only differ in phase in the frequency domain. Joe was concerned that white noise wouldn’t really have a constant power spectral density…. close, but not really constant. He gave his example and challenged me to produce one that did. I can, using random numbers from a software random number generator and deliberately forcing it to match the definition for white noise below. I assume that his example was also computer generated, meaning he also used a pseudo-random computer algorithm to produce “random” values. Also notice that neither one of us can produce a true impulse. It all computer numerical games missing the point that phase is required!!

Here is the definition of white noise that you provided:

"In signal processing, white noise is a random signal with a constant power spectral density."

The definition of random is quite important to the discussion.

SO IS “constant power spectral density”!! But the whole white noise issue is stupid and diversionary, and I mentioned more than once that white noise is not the issue, PHASE IS! Read the thread!

Please! Read the thread and don't keep up the white noise nonsense. It's just adding noise I'm done with it if people would drop it.
It's not important.

 

[RRod]

***, enough about white noise already. You can make a digital signal whose FFT is flat in magnitude but that sounds like "shhhhhhhhhhhhhh" because of pseudo-random phase. Let's just end it there.

 

[SoundAndMotion]

***, enough about white noise already.

***, I agree.

Do you see the necessity of phase (with magnitude, or alternatively: real and imaginary) for a frequency domain description of a signal?

 

[RRod]

***, I agree.

Do you see the necessity of phase (with magnitude, or alternatively: real and imaginary) for a frequency domain description of a signal?

 
I think the question is: do we ever get into audible phase issues in our attempt to fix FR. Any device that flattened magnitude but turned phase into a bad Seurat painting probably isn't one anyone ever really uses for music.

 

[SoundAndMotion]

I think the question is: do we ever get into audible phase issues in our attempt to fix FR. Any device that flattened magnitude but turned phase into a bad Seurat painting probably isn't one anyone ever really uses for music.

That is not my question; you are sidestepping my question.
You would very much get into "audible phase issues" if you attempted to "fix FR" by FFTing your signal, discard phase and just apply your desired FR to the magnitude, and then IFFT with "nice, flat" zero phase. Yes, I know this is not how any audio software would do it. But someone playing around with Matlab and reading what others say might. My point is you have to keep track of phase and either do what you want to it (for your own reasons) or leave it untouched (by keeping track of it). In a previous post, it was stated by another member that only magnitude and frequency are needed for a full description. My point is that's false. NOT anything about "audible phase issues" coming from software that "anyone ever really uses for music", except some people, including researchers, use Matlab to manipulate sound files.

 

[RRod]

That is not my question; you are sidestepping my question.
You would very much get into "audible phase issues" if you attempted to "fix FR" by FFTing your signal, discard phase and just apply your desired FR to the magnitude, and then IFFT with "nice, flat" zero phase. Yes, I know this is not how any audio software would do it. But someone playing around with Matlab and reading what others say might. My point is you have to keep track of phase and either do what you want to it (for your own reasons) or leave it untouched (by keeping track of it). In a previous post, it was stated by another member that only magnitude and frequency are needed for a full description. My point is that's false. NOT anything about "audible phase issues" coming from software that "anyone ever really uses for music", except some people, including researchers, use Matlab to manipulate sound files.

 
Quit making it a fight, jeebs. I agree with you: a complete picture of the linear performance of a system requires phase. That isn't even debatable, so why even debate it?

 

[SoundAndMotion]

Quit making it a fight, jeebs. I agree with you: a complete picture of the linear performance of a system requires phase. That isn't even debatable, so why even debate it?

It has not been my intention to fight with you. Sorry.
I intended to make one post (#52) in response to post #50. If the poster from #50 wanted further discussion, I would have continued. If not, I was done.
Since then I have been defending my post (#52) about phase, from challenges w.r.t. phase distortion, WN and randomness. I see these distractions as a way to avoid #52 as a response to #50. Sorry, I included you in my attempts to remove the distractions, but you kind of jumped into the fray.

 

[old tech]

  I understand what you are saying about pre and post ringing. I'm interested in reading the Meyer & Moran paper as well (although it costs money so I am not likely to). But I would ask, how do we know these things? How do we know that pre and post ringing can only be heard under certain conditions? How did Meyer and Moran make their determination? I am not asking you to give a complete explanation, but I'm not too impressed with what I've seen about psychoacoustics so far. The experiments seem to be run under pretty limited conditions or investigate a very small subset of phenomena.

Here you go
http://drewdaniels.com/audible.pdf