Sound Propagation Through a Grille

[strevo]

Hi guys. I've got a question that maybe some of the more experienced audio guys can answer. I'm working on a design project for work and we're looking to see if there's a general rule of thumb, or calculation to determine how much sound will make it's way through a molded plastic speaker grille. Basically, we have a small plastic box with a piezoelectric speaker in it capable of producing a certain dB level. The box has some small holes in it near the speaker. We need to know if there's an easy way to determine the dB drop outside of the box without resorting to CFD software. If anybody has any ideas, I'm all ears. Thanks!
-Steve

[madmac]

Easy!! Play the speaker at a given volume with the grill off and with a SPL meter, measure the average. You could also use pink noise which would be more accurate actually. Then after, put the grill on and measure again at the same volume. The difference will be your answer!!. Tadaaaa!!.

[strevo]

Thanks, but unfortunately these parts don't exist yet, so I need a theoretical way to do it, and the results will help to develop the design.

[wkhanna]

Maybe some of the gang over at the 'Mission Possible DIY' forum can lend a hand on modeling. I will see if we can have your post moved over there.

[baranowski]

heck, just leave the grill off, most people do that with fabric grills anyway

[mjb]

We need to know if there's an easy way to determine the dB drop outside of the box without resorting to CFD software.

You can't calculate it, you have to measure it! I can give you a box with 130db loss - a sealed box. Or perhaps one with 3db loss - the same box with the lid not properly closed. I can't calculate if the lid is on or not, but I sure can measure it!