I look into a french dictionnary...
Reflection (reflexion in french): from latin "reflexio" wich means "action to return".
Diffraction: from latin "diffringere" which mean "separate into pieces"
So, this two words expresse which is observable without associated each other.
If we use "diffraction" to refer the entire concept, it is also wrong to use "reflection".
For me, the concept is based on problem of space/time...
Space for directivity problems and time for group-delay problems, which I call the distortion from space/time domain.
Like distortion from linear or non-linear domain (for me "non-linear distortion" means nothing whatever language, for me it's the distortions from non-linear domain).
-------
linear domain : amplitude and phase distortions
Non-linear domain : harmonique and intermodulation distortions
Space/time domain : directivity and group-delay distortions
This is what I explain on this page (not yet translated):
http://thend.chez-alice.fr/Distorsion/Types.html
Reflection (reflexion in french): from latin "reflexio" wich means "action to return".
Diffraction: from latin "diffringere" which mean "separate into pieces"
So, this two words expresse which is observable without associated each other.
If we use "diffraction" to refer the entire concept, it is also wrong to use "reflection".
For me, the concept is based on problem of space/time...
Space for directivity problems and time for group-delay problems, which I call the distortion from space/time domain.
Like distortion from linear or non-linear domain (for me "non-linear distortion" means nothing whatever language, for me it's the distortions from non-linear domain).
-------
linear domain : amplitude and phase distortions
Non-linear domain : harmonique and intermodulation distortions
Space/time domain : directivity and group-delay distortions
This is what I explain on this page (not yet translated):
http://thend.chez-alice.fr/Distorsion/Types.html
The descriptive "diffraction" alone seems more appropriate to me. It's a single event. The described differences are based solely on the perspective of position. It would leave a conundrum. If it is reflection in the front hemisphere and diffraction in the rear hemisphere, what is the description at any point on the plane of the baffle beyond the edge of the baffle? Where does the transition in perspective from reflection to diffraction actually occur?thend said:
Dave
dlr said:
I prefere distortion of space/time domain because it's more big picture, "diffraction" discribe only one apsect, so it's not false but it's partial.
I imagined the distortion of space/time domain for crossover and physical position of loudspeakers wich create directivity lobes and most of personnality's speaker in its room.
But it's work for baffle and horn diffraction too, because the diffraction could be compare to a mutiple loudspeaker with a physical shift (comb filtering). It's not really the same thing but it falls within the concept of distortion of space/time domain. (and not the trekkie "space/time distortion")
I recognize that the distortion of the directivity can be ambiguous (distortion compared to what?), but it's the sound reproduction: the "high fidelity" which is ambiguous first.
For your questions, I don't really understand what you says (my english).
Hello,
Distortion is a deformation of signal.
Deformation of amplitude and phase in linear domain.
Deformation with added signal (harmonic distortion ...) in non-lineare domain
Time deformation like a bass that arrives before or after a treble and space deformation like directivity lobes or horn diffraction.
Indeed, Amplitude, phase, harmonic distortion, group delay and diffraction are descriptions of phenomena.
soongsc said:Distortion is relative, diffraction is a description of a phenomena.
Distortion is a deformation of signal.
Deformation of amplitude and phase in linear domain.
Deformation with added signal (harmonic distortion ...) in non-lineare domain
Time deformation like a bass that arrives before or after a treble and space deformation like directivity lobes or horn diffraction.
Indeed, Amplitude, phase, harmonic distortion, group delay and diffraction are descriptions of phenomena.
dlr said:
What I mean is that the reflection/diffraction (in topic, i guess) I place it in a domain of distortion.
We have the linear and non-linear domain, why not a space/time domain for acoustic transmission (mainly).
soongsc said:
I don't understand the relationship with the relativity?
soongsc said:
Actually I feel way more familiar with the visualisation part of math - geometry - and further on - with patterns.
So, for your question - no.
On the other hand the Gaussian algorithm / formula / curve has merits in utilising it for a horn contour.
It was just an inspiration when rcw was taking about what you have referenced and as can be seen it seems to work pretty well.
Michael
ScottG said:
Borrowing from a previous conversation with dlr, I think the difference is one of polarity, + or -.
A pressure wave spreading across the baffle will have high pressure (2pi radiation) that decreases when it gets to the baffle edge (4pi radiation). That causes a delayed negative spike in the impulse response.
If the wave hits a solid obstacle like a grill frame, it will cause a delayed positive spike in the impulse. That's followed by a negative spike as it gets to the outside of the frame.
When we talk about distortion, it's relative to the original signal.thend said:
When we talk about diffraction, we are talking about a physical phenomena. Distortion can be explained to be a cause by diffraction waves interacting with the original wave.
It seems to confuse the issue to place diffraction in the domain of distortion.
dlr said:
Dave
This is precisely correct and why most people do not distinguish reflection from diffraction in most cases, the two are simply termed "diffraction". In the case of a waveguide however the ambiguity is mostly resolved and there can be a rational for discussing the two seperately and I, myself, sometimes do that. Most of the time this is not a problem, but in discussions here I have seen it misundertood and misused. I would prefer that we all understood the situation perfectly, but alas, that is not to be.
Hello,
I understand that it's difficult to consider diffraction like distortion.
But more than the diffraction, it's directivity that I regarded as a spatial distortion.
This is the distribution of each frequency in the space must be uniform, consistent between each ways of speaker.
In this case, it's not really the natural phenomena or the pure acoustician point of view that we consider, it's the technicals caracteristics of speaker, like in linear and non-linear domain.
And diffraction disrupts this spatial distribution (the directivity).
I understand that it's difficult to consider diffraction like distortion.
But more than the diffraction, it's directivity that I regarded as a spatial distortion.
This is the distribution of each frequency in the space must be uniform, consistent between each ways of speaker.
In this case, it's not really the natural phenomena or the pure acoustician point of view that we consider, it's the technicals caracteristics of speaker, like in linear and non-linear domain.
And diffraction disrupts this spatial distribution (the directivity).