AFMG Network Forum

javinhood · Member

Hi,

I am trying to simulate sound coverage in indoor scenarios. I have found strange results, so I wonder if I am using the wrong settings/simulation?

This is the setup I am using:
- I use double side generic absorber for all the external walls, floor and ceiling.
- I have tried different wall materials for the inner walls - similar results.
- Total SPL 2D simulation
- Map with shadow.

I am doind simulations of the sound level in adyacent rooms within a building. Say for example there are three rooms in a row, and I place a speaker in the first one. The sound level calculated for the second and third room is exactly the same, even if the distance to the third room is bigger and of course the sound needs to go through two walls for the third room and only through one wall for the second room -> walls not taken into account, and distance not taken into account.

Other thing that I do not understand: If there is an obstacle in the room, say a piece of wall, the sound calculation is only done in the area of the room with direct line of sight from the speaker. The rest is left with and adverage constant sound level, not variating with distance (even if it is part of the same room.

Could please anyone explain these effects? I do not know if this is normal, or if I have the wrong settings/type of simulation, or what.

Any help is welcome.

Thank you!

Charlie · Member

The line of sight issue you describe is due to using the Map With Shadow option. The obstacle casts an acoustical shadow.

Since you are mapping the Total SPL, the SPL shown in the shadow region is the SPL of the reverberant field. If you mapped the Direct SPL the shadow region would show no SPL.

javinhood · Member

Thanks for your answer.

I used the Map With Shadow option because otherwise walls and objects have no effect in the room.

One of the things that confuses me is the fact that all the shadowed area behind a wall have a constant SPL. Is it a real effect or just and aproximation of the software?

My example: If I have a speaker in a room, and want to analyze the effect of this speaker in an adyacent room, how can I do it? In other words, I would like to simulate the transmission of the sound through the walls from one room to another, and may be to a third one.
- If I use Direct SPL without shadow effect, the effect of the transmission losses through the wall are not taken in to account (or I do not know how to do it) and as far as I know only free space propagation losses are taken into account.
- If I use Direct SPL with Map With Shadow, I get black area in the shadowed area. Again, no transmission through the walls).
- Total SPL without shadow effect -> very similar result to the first case and no transmission effect.
- Total SPL with Shadow effect -> no direct rays to the next room? the flat colour that i get behindthe wall is just part of .. reverb.? from where?

Sorry for all this writing, but I think I am missing some point here. The reflection coeffitient of the wall material says how much of the power will be reflected, but, does it mean that the rest of the power will be just absorved by the material? Or some will also be transmitted? How much?

Thanks again fro trying to bring me out of this..

AFMG Pedro Lima · Forum Moderator

Dear javinhood,

It seems there is actually a conceptual problem.

EASE is a tool to assist you on arqchitectural acoustics related tasks. In EASE, you are generally interested in one acoustical space and it will not simulate the transmission throught walls or structures. It's background is based on geometrical acoustics.

The walls/faces in EASE are modeled based on the absorption (and scattering) coefficients of the materials that compose the wall.

In order to simulate transmission loss and other building acoustics related parameters, take a look at SoundFlow: http://soundflow.afmg.eu/

You can download a trial (fully functional) version, and test the program for 30 days.

Whenever Standard Mapping is selected, the Reverberant Energy part for the Total SPL is calculated based on Eyring/Sabine formulas for the room.

Please see the EASE tutorial for more information on the calculated parameters: http://ease.afmg.eu/index.php/documents.html

Also, in the user manual, which can be found in general under: C:\Program Files (x86)\EASE 4.3\Easepath\Ease43Manual, there is the comprehensive appendix A (Room-acoustical Fundamentals for Auditoriums and Concert Halls), where you can find more specific info about the calculation engines.

Hope this helps.

Best Regards,
Pedro

javinhood · Member

Thanks Pedro, this explains most of my problems.

However, if there is no transmission simulated through walls, how can I end up with some SPL in a room where there is no speaker? should the reverb. sound created in the room with speaker just stay in that room, instead of coming to the other room?

Regarding what you mentioned about SoundFlow, please let me know if it might be useful for my interest. Can I just create a material with a given reflection, absortion and transmission coefficient, so I can use it afterwards in EASE and check transmission of sound between rooms? I tried to do it but the trial version does not let me save the material.

Thanks again!

Tim · Member

javinhood,

EASE is a design tool for evaluating architectural acoustics and electro-acoustics within a closed room. It is not possible to evaluate sound transmission between two or more adjoining closed rooms. At this stage only material absorption and simple scattering can be modelled in EASE.

"how can I end up with some SPL in a room where there is no speaker?"
Is your model 'closed'? Go to the Edit > Room Data dialogue box and uncheck the 'Room open' tick box.

SoundFlow is a design tool for evaluating absorption, transmission + reflection of acoustic energy for a given material or wall system. The licensed software allows exporting of material absorption + scattering to an EASE material file for use in an EASE model. If you are using the evaluation version, you can view the results in a table and recreate these as a material in EASE - manually entering the data.

If you haven't done so already, I would highly recommend working through some of the EASE tutorials. These give a great understanding of how EASE works and what you might expect to get out of the software.