AFMG Network Forum
AFMG Network Forum Index -> EASE 4 -> DirectSPL vs. TotalSPL
Post new topic  Reply to topic View previous topic :: View next topic 
DirectSPL vs. TotalSPL
PostPosted: Mon Jan 25, 2016 4:52 pm Reply with quote
AlexandreF
Member
 
Joined: 25 Jan 2016
Posts: 3




I have performed standard mapping on a closed model and for some areas the maximum value of the DirectSPL is higher than the maximum value of the TotalSPL.
On the other hand, average directSPL values are always lower than average TotalSPL, as expected.

Any reasoning to this situation?

Any help appreciated. Thanks in advance.
View user's profile Send private message
PostPosted: Tue Jan 26, 2016 10:56 am Reply with quote
AFMG Frank Siegmann
Member
 
Joined: 18 Jul 2005
Posts: 236




Did you calculate "Interference Sum"? If yes, due to the sound wave superposition for some areas the Direct SPL can be higher than the Total SPL, because Interference is only applied for Direct SPL.

Frank Siegmann
AFMG
View user's profile Send private message
PostPosted: Tue Jan 26, 2016 7:19 pm Reply with quote
AlexandreF
Member
 
Joined: 25 Jan 2016
Posts: 3




Thanks for the reply Frank.

Yes, interference sum is always checked for both pot. and kin. energy. 1/3 octave also checked.

So from my understanding:

Direct SPL --> evaluates SPL coverage (1st incident sound wave only) plus phase interference from another sources (if interference sum checked).

Total SPL --> evaluates SPL coverage (1st incident sound wave and subsequent reflections) for each sound source independently.

Direct SPL can be higher (in some specific areas) due to real time phase interference.
Total SPL represents the most approximate SPL coverage value for an area due to the architectural model contribution (reverberant component).

Is this fair to conclude?
View user's profile Send private message
PostPosted: Wed Jan 27, 2016 12:33 pm Reply with quote
AFMG Frank Siegmann
Member
 
Joined: 18 Jul 2005
Posts: 236




Yes, that's right.

Frank
View user's profile Send private message
PostPosted: Wed Jan 27, 2016 11:48 pm Reply with quote
AFMG Pedro Lima
Forum Moderator
 
Joined: 05 Jun 2010
Posts: 266
Location: Germany




Hello Gentlemen,

Just to complement the thoughts: when using Standard Mappings with Reflections, the contributions from these reflections are also calculated considering the Interference Sum check box.

Regards,
Pedro
View user's profile Send private message
PostPosted: Wed Jan 27, 2016 11:50 pm Reply with quote
AFMG Pedro Lima
Forum Moderator
 
Joined: 05 Jun 2010
Posts: 266
Location: Germany




Hello Gentlemen,

Just to complement the thoughts: when using Standard Mappings with Reflections, the contributions from these reflections are also calculated considering the Interference Sum check box.

Regards,
Pedro
View user's profile Send private message
PostPosted: Thu Jan 28, 2016 6:41 pm Reply with quote
AlexandreF
Member
 
Joined: 25 Jan 2016
Posts: 3




Hi Pedro, thank you for your contribution.

Your last comment somewhat confused me in regards to DirectSPL max values being higher than TotalSPL max values.

So Interference Sum (if checked) is considered for both Direct & Total SPL evaluation on standard area mappings? If this is the case (like you said on previous post) then TotalSPL max values should always be higher than Direct SPL max values, right?

Maybe I'm missing something from acoustics theory. Is there a practical explanation as to why this occurs for some specific areas?

Ease v4.3 User Manual points Interference Sum to DirectSPL calculation on page 204. I use EASE v4.4 with the following parameters in all calculations (if it helps):
• Split time: 35 ms
• Map on areas
• Noise: custom input
• Isoline: 1db
• Scale (m): 0.1
• Map with shadow: checked
• Interference: checked
• Pot. energy: checked
• Kin. Energy: checked
• 1/3 octave: checked

Thank in advance.

Regards,
Alexandre
View user's profile Send private message
PostPosted: Thu Jan 28, 2016 6:48 pm Reply with quote
AFMG Pedro Lima
Forum Moderator
 
Joined: 05 Jun 2010
Posts: 266
Location: Germany




Hi Alexandre,

Notice that in EASE > Standard Mapping you can make these two types of simulations:
- Standard Mapping
- Standard Mapping with Reflections.

The second will consider, in addition to the statistical Reverberant field, the contribution from reflections calculated with Ray Tracing routines. The Reflections order is defined by you. For instance, you might want to check only reflections up to the 3rd order. THESE ones will be summed in a complex manner (if interference sum is checked).

The Total SPL in this case will be the sum of the Direct Sounds + (statistical) Reverberant Field + the First Reflections (the limit is defined by you).

So, the Reverberant field is still considered as Frank said above.

HTH,
Pedro
View user's profile Send private message
AFMG Network Forum Index -> EASE 4
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 1  

  
  
 Post new topic  Reply to topic  


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