Reverberant field spl calculation - AVS Forum
Forum Jump: 
 
Thread Tools
post #1 of 2 Old 07-14-2013, 05:01 PM - Thread Starter
Okv
Member
 
Okv's Avatar
 
Join Date: Jul 2010
Location: Aalesund, Norway
Posts: 165
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 27 Post(s)
Liked: 38
I am putting up a calculator for speaker requirements on my web site, for speaker sensitivity, amplifier power and sound pressure level estimations.

Using information about room and speaker and speaker placement, the spl is estimated by summing the direct sound and the reverberant field.
Direct sound is easy, but I have not been able to find consistent information for the reverberant field calculation, valid in a small room with relatively much acoustic damping.
I have found different fomulas suggested, that will give different results.

So far, this is pretty much what I have now:
- Rx, the critical distance, is where the revb spl equals the direct.
- At least 2 formulas:
Rx=0.141*sqrt(G*A'), where A' is the room constant = f(V, T60, abs area), G=source directivity.
Rx=0.057*sqrt(G*V/T60), where G=source dir.
- Revb spl can then be calculated by using Rx.
- A correction factor for the revb spl can compensate approximately for the fact that the revb sound field is not constant in a small damped room, it will fall as a function of distance from the source.
[http://www.jblpro.com/pub/manuals/pssdm_1.pdf, page 58].

If someone have an idea, or even some good measurements of spl vs. distance from source in a room, that could be helpful.

If the relationship between room data (V and T60) and spl as a function of distance from the source can be established, then it will be possible to make a sufficiently accurate correction.
This does not need to be very accurate, that is also impossible with reasonable amount of data entered into the model (i.e. room dimensions and T60), but it can still be sufficient to give a good estimate.

All rooms considered as useable here will fall into the category of small and damped.
In such rooms the direct sound will be large compared to the reverberant field, in most cases larger than the revb, so that an error in estimated revb spl will not have a proportional impact on the total estimated spl.
Okv is offline  
Sponsored Links
Advertisement
 
post #2 of 2 Old 07-16-2013, 12:59 PM - Thread Starter
Okv
Member
 
Okv's Avatar
 
Join Date: Jul 2010
Location: Aalesund, Norway
Posts: 165
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 27 Post(s)
Liked: 38
Solved, by using the formula based on room-constant, and an estimate for absorptive area.
Should be reasonably accurate for small, damped rooms, where the revb sound field is not that dominant, so that a small error will not have a large effect on the calculated response.

Green = calculated.

Okv is offline  
Reply Audio theory, Setup and Chat

User Tag List

Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page


Forum Jump: 

Posting Rules  
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off