 Posted: Mon Jan 25, 2016 4:52 pm |
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| 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. |
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| Posted: Tue Jan 26, 2016 10:56 am |
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| 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 |
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| Posted: Tue Jan 26, 2016 7:19 pm |
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| 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? |
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| Posted: Wed Jan 27, 2016 12:33 pm |
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| Posted: Wed Jan 27, 2016 11:48 pm |
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| AFMG Pedro Lima |
| Forum Moderator |
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| Joined: 05 Jun 2010 |
| Posts: 269 |
| Location: Germany |
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| 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 |
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| Posted: Wed Jan 27, 2016 11:50 pm |
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| AFMG Pedro Lima |
| Forum Moderator |
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| Joined: 05 Jun 2010 |
| Posts: 269 |
| Location: Germany |
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| 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 |
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| Posted: Thu Jan 28, 2016 6:41 pm |
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| 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 |
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| Posted: Thu Jan 28, 2016 6:48 pm |
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| AFMG Pedro Lima |
| Forum Moderator |
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| Joined: 05 Jun 2010 |
| Posts: 269 |
| Location: Germany |
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| 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 |
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