AFMG Network
Forums for AFMG Software
AFMG Network Forum Index -> EASE - Discussion -> What I need to look for in a Ray Tracing Impacts? Goto page 1, 2  Next
Post new topic  Reply to topic View previous topic :: View next topic 
What I need to look for in a Ray Tracing Impacts?
PostPosted: Sat Mar 18, 2017 12:03 am Reply with quote
opacheco
Member
 
Joined: 01 Dec 2009
Posts: 60




Hi,

I have done a Ray Tracing Impacts test in a Room but am not so clear in this theme but What is a Good Raytracing Impact Response? What I need consider for get a better response (Tips)??

Any advise will be appreciate so much!


Thanks anticipated
Opacheco.

_________________
Thanks a lot for comments!
Opacheco.
View user's profile Send private message Send e-mail Yahoo Messenger MSN Messenger
PostPosted: Mon Mar 20, 2017 4:32 pm Reply with quote
opacheco
Member
 
Joined: 01 Dec 2009
Posts: 60




Any Comment?

Opacheco

_________________
Thanks a lot for comments!
Opacheco.
View user's profile Send private message Send e-mail Yahoo Messenger MSN Messenger
PostPosted: Tue Mar 21, 2017 12:31 pm Reply with quote
Agustín Arias
Member
 
Joined: 10 Apr 2013
Posts: 18
Location: Hurlingham, Buenos Aires, Argentina




Hi Opacheco.
This is a very very very very.... .... very simple idea of how to start your first raytracing. Remember, it's all about practicing, gaining experience and using your judgment about how to interpret the results delivered by EASE











_________________
Eng. Agustín Arias
Environmental Protection Agency, Buenos Aires, Argentina
Ottobre & Ottobre, Acoustical Consultants, Buenos Aires, Argentina
e-mail: agustin.arias@outlook.com
View user's profile Send private message Send e-mail Visit poster's website
PostPosted: Tue Mar 21, 2017 9:26 pm Reply with quote
opacheco
Member
 
Joined: 01 Dec 2009
Posts: 60




Agustin,
Thanks for your comments!

I have not any trouble in to do the simulation in EASE, that isn't the problem but How I can know if I get a GOOD Raytracing Impact response in a particular audience spot?, How can I to know if a response is BAD??....I think this more an Early Reflection response interpretation.....Do you know how Interpret this kind of graph??, Do exist a guidelines for that?

I would like to get a more scientific interpretation in order to get the correct judge about the Early Reflection understanding.....Do you??

Opacheco.

_________________
Thanks a lot for comments!
Opacheco.
View user's profile Send private message Send e-mail Yahoo Messenger MSN Messenger
PostPosted: Thu Mar 23, 2017 9:11 am Reply with quote
Frank Siegmann
Member
 
Joined: 18 Jul 2005
Posts: 112




Hi Opacheco,

you can use the Probe acoustical analysis program module and its wide range of acoustical analysis tools to inspect the impact response (Reflectogram). See also Chapter 10 of the EASE Tutorial ( http://ease.afmg.eu/index.php/documents.html ).

Frank Siegmann
View user's profile Send private message
PostPosted: Thu Mar 23, 2017 2:08 pm Reply with quote
thomas
Member
 
Joined: 16 Mar 2011
Posts: 42




Hi Opacheco,
the question "What is a Good Raytracing Impact Response?" is a little bit
like the question "What is good acoustic?". It's not possible to answer that question.

I suppose you should look at all the parameters, that can be calculated
from that response. And than bring them in the optimal range for the
usage of your room.
Interpretation of a reflectogramm is a really challenging thing that
requires a solid professional background and tons of experience.

If "good" means "a reliable result of simulation", the hints of Augustin and
Frank are good points to start with. And always look at the result
(reflectogram) and ask you: Is what I see a result of acoustic or an effect
of simulation? E.g. strange spikes in the reflectogram after some hundred
ms have often no acoustic origin, but unfavorable choosen parameters for
simulation. Change parameters and look, what changes in the response.

thomas
View user's profile Send private message
PostPosted: Thu Mar 23, 2017 3:50 pm Reply with quote
opacheco
Member
 
Joined: 01 Dec 2009
Posts: 60




Thomas,

Thanks for your advises!

I know this is a experience theme response but I thought I could get some advises like exist in similar situations i.e., Room Modes using the Bonello Criteria or the maximum Numbers of near Modes in a spot freq response or something like this!!!.....

-------------

I refuse to believe today the twenty-first century doesn't exist guidelines at least in order to interpret or evaluate the Early Reflection Curve Response and its possible empirical or technical or scientific solutions in a criteria level!!.

Well if somebody have an empirical method (but with experience criteria) for analysis or diagnostic evaluation of Raytracing Impact or Early reflections graph, please let me to know and I will be forever grateful.......

Opacheco.

_________________
Thanks a lot for comments!
Opacheco.
View user's profile Send private message Send e-mail Yahoo Messenger MSN Messenger
PostPosted: Thu Mar 23, 2017 6:11 pm Reply with quote
Agustín Arias
Member
 
Joined: 10 Apr 2013
Posts: 18
Location: Hurlingham, Buenos Aires, Argentina




Hi Opacheco.
Here is some iformation about early reflections.

1) Book: Architectural Acoustics - Marshall Long

Early Reflections, Intimacy, and Clarity
The importance of early reflections has been recognized for some time. Vitruvius (1960), the Roman architect, extolled the value of what the Greeks called consonant sound or sound that is supported and strengthened by reflections from the stage and other nearby surfaces. Sabine (1964) referenced Vitruvius and also spoke of the need for reflections from surfaces that do not have too great a path length difference at the receiver. Beranek (1962) defined the initial time delay of the first reflection, tI , as the property he calls intimacy. Barron (1993) gave a slightly different definition, which is the sense that music is being played in a small room. In his 1996 work, Beranek changed his definition, saying that it is the sensation that sound is being played in an appropriately sized room, which he characterizes primarily in terms of initial delay gap, but which also relates to loudness.
The initial delay time is the difference in milliseconds between the arrival time of the strongest reflection, minus the arrival time of the direct sound, at the center of the audience seating area. In 1962 Beranek considered this to be the most important factor in concert hall quality, assigning a maximum of 40 points to halls having an initial time delay of 20 msec or less, reducing credit linearly to zero when the gap is above 70 msec. In his later (1996) study this was reduced to 10 points maximum. He still maintained 20 msec as the threshold but held that beyond 35 msec quality suffered substantially. Ando’s concert hall studies confirmed the importance of early reflections, although his test reflection was from the side, positioned at an angle about 36◦ from the centerline in the horizontal plane. Ando also found that the preferred initial delay time was just under 20 msec.
Barron (1993) reasons that intimacy is not precisely the same as early delay time. The sense that one is in a small room with the musicians is experienced by sitting near the players, irrespective of the delay. Indeed the gap is often greatest at locations closest to the orchestra.

If intimacy were only dependent on the delay gap, he argues, the sound should always be more intimate at the rear of a hall, where the time gap is the smallest. Subjective surveys by Hawkes and Douglas (1971) and Barron (1988) have shown the opposite to be the case. Since the value of tI depends on where the listener is seated, Barron also asks if it is appropriate to use a single number to characterize an entire concert hall. The difference here is primarily one of definition, since Beranek (1962) and Ando (1985) define intimacy as initial delay time, and Barron as the sense that one is in a small room.
The early-to-late signal-to-noise ratio, C80, is also used in musical acoustics. Called the clarity factor in concert hall analysis, it is the ratio of the sound energy arriving before, to that arriving after, the first 80 milliseconds from the arrival of the direct sound, expressed as a level. It is measured in an unoccupied room and contains more information than the initial time delay, which does not account for the strength of the early reflections.
Just as with speech intelligibility, a high signal-to-noise ratio, which results from strong early reflections, yields musical clarity. Values of the C80, which can range from small positive numbers, implying a dead room, to small negative values for very reverberant spaces, fall into the ± 4 dB range. The preferred values of C80 are between 0 and −4 dB. Several highly successful halls: Boston, Amsterdam, and Vienna, have C80 (3) values (Beranek, 1996) that are between −2.7 and −3.7 dB. The (3) means that three C80 values, those in the 500, 1k, and 2k Hz octave bands, are averaged.

Early reflections are important to the appreciation of rapid musical passages and passages played by the quieter instruments such as the harpsichord, recorder, and guitar. Convex surfaces are placed above the orchestra, at a height of around 20 feet, to provide reflections back to the musicians and the audience seated on the main floor. For reinforcement over a wide frequency range, the individual panels should be relatively large, at least 6 feet (1.8 m) long, and arrayed across the entire width of the orchestra. A slight lateral convexity helps to fill in the gaps left by the space between panels. Longitudinal convexity compensates for changes in instrument or performer location. Cremer and Muller (1982) recommend a minimum open area of about 70%, with many small clouds being preferred to a few large reflectors, to insure coupling between the upper and lower volumes of the hall.
Sidewalls provide the necessary early reflections for the audience seated toward the rear of the concert hall. In rectangular rooms these are parallel. In surround halls local reflecting surfaces must be carefully crafted to fill in the needed reflections. The high ceiling is designed to be diffuse and thus is not particularly useful for this task.

2) Book: Acoustics and Psychoacoustics, Fourth Edition - David Howard, Jamie Angus

A little time later the listener will then hear sounds which have been reflected off one or more surfaces (walls, floor, etc.), as shown in Figure 6.3. These sounds are called early reflections and they are separated in both time and direction from the direct sound. These sounds will vary as the source or the listener moves within the space. We use these changes to give us information about both the size of the space and the position of the source in the space. If any of these reflections are very delayed, i.e.,
total path length difference longer than about 30 milliseconds (33 feet), then they will be perceived as echoes. Early reflections can cause interference effects, as discussed in Chapter 1, and these can both reduce the intelligibility of speech and cause unwanted timbre changes in music in the space.

The intensity levels of the early reflections are affected by both the distance and the surface from which they are reflected. In general most surfaces absorb some of the sound energy and so the reflection is weakened by the absorption. However, it is possible to have surfaces which “focus” the sound, as shown in Figure 6.4, and in these circumstances the intensity level at the listener will be enhanced. It is important to note, however, that the total power in the sound will have been reduced by the interaction with the surface. This means that there will be less sound intensity at other positions in the room. Also any focusing structure must be large when measured with respect to the sound wavelength, which tends to mean that these effects are more likely to happen for high-, rather than low-frequency components. In general therefore
the level of direct reflections will be less than that which would be predicted by the inverse square law, due to surface absorption. Let us calculate the amplitude of an early reflection from a loudspeaker.

_________________
Eng. Agustín Arias
Environmental Protection Agency, Buenos Aires, Argentina
Ottobre & Ottobre, Acoustical Consultants, Buenos Aires, Argentina
e-mail: agustin.arias@outlook.com
View user's profile Send private message Send e-mail Visit poster's website
PostPosted: Thu Mar 23, 2017 10:10 pm Reply with quote
opacheco
Member
 
Joined: 01 Dec 2009
Posts: 60




Agustin,
Very interesting and clear; the It, intimacy (Barron definition), C80 and C50 concept help a lot to understand and interpret the Early Reflection Curve. Thanks!

I found this comments about nearly I am searching for:

The three most important things we want to see in an ETC test are:

http://www.gikacoustics.com/wp-content/uploads/2016/11/Fig-2-Impulse-ETC-response-first-spikes-circled.png

1. A smooth decay of spikes. Each spike should be softer than the previous one, without any “ripples” where softer spikes precede louder ones in time. The above graph in Figure 2 is therefore NOT representative of a great room decay, since there are several spikes louder, at about 12, 19, and 22 ms, than previous spikes.

2. Spikes softer within the echo threshold. Spikes within 0 (the initial transient) out to 20-40ms or so should be down by 10-20dB. Opinions vary on the exact numbers of this precedence effect, but at GIK, some of the better rooms we have seen will show them down by 15-20dB within 20ms. Rooms with these characteristics are less psychoacoustically jumbled, the stereo image is more distinct, with a more realistic soundstage and greater articulation and intelligibility during listening. Figure 2 does pretty well on this, since all of the spikes after 20ms are down 20dB except one, which is at 15dB.

3. Graphs for all the speakers match, as closely as possible. They will never be exactly the same, but the closer they match the better. The more symmetrical the room is, the better the chance that the graphs for all speakers will match. We know all rooms will color the sound we hear to some degree, we just want to both minimize the coloration and make sure each speaker, if must be colored, will be colored in the same way. If our rooms are not symmetrical, then we can use various treatments to try to restore some acoustic symmetry to a physically asymmetrical room, and use the results of this test – along with critical listening to familiar music – to evaluate our progress.


Opacheco.

_________________
Thanks a lot for comments!
Opacheco.
View user's profile Send private message Send e-mail Yahoo Messenger MSN Messenger
PostPosted: Fri Mar 24, 2017 1:05 pm Reply with quote
thomas
Member
 
Joined: 16 Mar 2011
Posts: 42




Hi Opacheco,
I hope You are aware, that the gikacoustic article You cited is about and only about the situation in
listening rooms (control rooms) of recording studios. Agustin wrote about a complete different thing -
about concert halls and in his second part about general aspects. If You deal with rooms for speech,
rooms for other kinds of music or with a church, things are different.

Btw, I think the statement
Quote:

If any of these reflections are very delayed, i.e., total path length difference longer than about 30
milliseconds (33 feet), then they will be perceived as echoes.

in the general part (point 2)) is really nonsense. Wether a person percieves an reflection or a group
of reflections as an echo ("perceives the signal twice") or not, depends mainly on
- time structure of the signal,
- length of the gap before that reflection/group of r.s,
- the relative level of that reflection/group of r.s,
- the background level,
- the ears of the listener.
If the general "echo-limit" of 30 ms would be right, every room with one dimension > approx. 6 m
would produce echos. I never heard an echo in such small rooms.

thomas
View user's profile Send private message
PostPosted: Fri Mar 24, 2017 2:54 pm Reply with quote
opacheco
Member
 
Joined: 01 Dec 2009
Posts: 60




Thomas,

Thanks a lot for comment.

This is your perception no the Scientific data at all!!.....I understand the rooms for listener and room or auditorium for another uses are deferents early reflection performer, but in general and according to the C80, C50 and stuff like this (objetive data no Subjective !!) are saying the same information about the smooth early reflections in the 0ms-40ms area, but (and I am not wanted to bother you!!) if you have scientific data in order to support that you said, that info is the I want to know; this post is for your experience with responsibility, with scientific data (not your perception) about the aspects to consider in order to have a "good"early reflection measurement or simulated by EASE in a general room....from 0ms - 40ms.

I hope you can understand because all I want to have is a real scientific and technical analysis about the early reflections and its implication using the response curve for that.

Opacheco.

_________________
Thanks a lot for comments!
Opacheco.
View user's profile Send private message Send e-mail Yahoo Messenger MSN Messenger
PostPosted: Sat Mar 25, 2017 11:06 am Reply with quote
thomas
Member
 
Joined: 16 Mar 2011
Posts: 42




Hi Opacheco,

1) There is no "general room" (without proof).
2) What reflections are "early", "late" or in the reverberant tail depends on the
room size. Therefor there is no general time for the end of early reflections.
(without proof, basic knowledge for people dealing with room acoustic)
3) Favored values for parameters (T, EDT, C50, C80, EK ...) are different for
different uses. (also basic knowledge, see e.g. Everest,A: Master Handbook of
Acoustics *), chapter 6 , or appenix A in the EASE Help)

-> The use of general statements is very, very limited Wink .

4) The scientific proof for the echo stuff I wrote you can find here:
- Dietsch, L.; Kraak, W.: „Ein objektives Kriterium zur Erfassung von Echostörungen
bei Musik- und Sprachdarbietungen“, Acustica, Vol. 60, 1986, S. 205 ff. (drivation of
the echo criterion, also used in EASE, with an overview of the prooven knowledge and
investigations of the subjective relevance of the EK)
or in
- Kuttriff: Room Acoustics

cheers,
Thomas

---------------
*) correction:
Ballou, Glenn M. (Editor): Handbook for Sound Engineers, Chapter 6
Neertheless I can recommend Everest, but not for this.


Last edited by thomas on Sat Mar 25, 2017 7:07 pm; edited 1 time in total
View user's profile Send private message
PostPosted: Sat Mar 25, 2017 5:23 pm Reply with quote
opacheco
Member
 
Joined: 01 Dec 2009
Posts: 60




Thomas

Well may be a make a mistake....you are right; there is not general room but Do exist generals rules in order to evaluate an Early Reflections (you know, early reflection do exist 0ms to 40ms and this is scientific documents around!!) in "diferents" kind of room (auditorium, listener room, rock concert room, classical music room.....)??

I thinks that like the Room Modes situations, don't exist a specific response that we need to reach (the persecuted objetive response!) but we have A LOT OF criteria from many researchers and experimental data out there!!!!......We need to think about this question in that point of view!!....CRITERIA for Early Reflection.

I don't follow the idea early reflection response is unique for each room, THAT IS TRUE!! but we need generals CRITERA beforehand in mind for the each specific room (auditorium, listener room, rock concert room, classical music room.....) in the way like gikacoustic article I cited....and must be similar to another kind of room, with scientific data of course...do you?

Any comment will be appreciate.
Opacheco.

_________________
Thanks a lot for comments!
Opacheco.
View user's profile Send private message Send e-mail Yahoo Messenger MSN Messenger
PostPosted: Sat Mar 25, 2017 7:41 pm Reply with quote
thomas
Member
 
Joined: 16 Mar 2011
Posts: 42




Quote:
I don't follow the idea early reflection response is unique for each room ...

I neither do. The impulse response, is roughly speaking unique for each sourceposition-room-listenerposition,
not for the room.

Quote:
but we need generals CRITERA beforehand in mind for the each specific room (auditorium,
listener room, rock concert room, classical music room.....) in the way like gikacoustic article
I cited....and must be similar to another kind of room, with scientific data of course...do you?

I'm afraid, I don't understand Your question.
Is it about
- quality (e.g. "a reflection at time x shouldn't exceed y dB compared to direct sound") or
- the method of examination (e.g. the modified ETC in the gikacoustic article), or
- anything else?

thomas
View user's profile Send private message
PostPosted: Sat Mar 25, 2017 8:02 pm Reply with quote
opacheco
Member
 
Joined: 01 Dec 2009
Posts: 60




Sorry my English isn't so good !

Of course I talked about the Room in sense each position!!.....

Yes quality if could I get a RULE like you told for specific room, auditorium, concert hall, rock room will be fantastic!......like you told: e.g. "a reflection at time x shouldn't exceed y dB compared to direct sound"!.....

My concise question is about to find or know the actuals methods or criteria for evaluate the quality of a early reflection in a spot (or spots in a room) response; What can I need to see for declare it's good response or if I need to work in order to get a correction in that early reflection spot measurement or simulation by EASE???

Do you know what I mean??

Thanks for your time and help.

Opacheco

_________________
Thanks a lot for comments!
Opacheco.
View user's profile Send private message Send e-mail Yahoo Messenger MSN Messenger
What I need to look for in a Ray Tracing Impacts?
AFMG Network Forum Index -> EASE - Discussion
You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum
All times are GMT  
Page 1 of 2  
Goto page 1, 2  Next
  
  
 Post new topic  Reply to topic  


Powered by phpBB © 2001-2003 phpBB Group
Theme created by Vjacheslav Trushkin
Variation by CodeWeavers