| In addition to other types, I've had good luck with perforated panel traps when tuned trapping is appropriate. However, measurements would indeed be necessary to know exactly where to tune it. However, an 8 inch cavity behind the panel filled with 4 inches of insulation will broaden the Q enough so that you can estimate a center frequency and have a decent margin of error. Everests Master Handbook of Acoustics has the info you'd need to figure hole size, spacing, and panel thickness, or you could use the Helmholtz equation and extrapolate out to make each effective "cell" behind each hole the appropriate volume. Of you could search for Mankovsky's writings. He did a boatload of work on the subject. It's an easy way to get deep bass absorption with only an 8 inch depth. |