As we know Maa et all have pioneered the theoretical calculations on Acoustics Impedance and Absorption by introducing the concept of micro-perforations. While preparing some theoretical predictions over the experimentally generated data many of the calculations in literature contradicts and seem a little confusing with imaginary terms and differential equations.
Are there any suggestions on some simplified calculations and methods that can be applied for theoretical modeling in MPP acoustics for the determination of Sound absorption Coeeficeint?
Dear Abhishek,
If I understand well your question, you are looking for a simple analytical model for the prediction of MPPs impedance.
Such model is given by Maa (1998) [Article Potential of microperforated panel absorber
], Eq. (5).Note that the impedance is a complex number.
I hope that helps
Dear Jean Boulvert Thanks for mentioning the relevant literature. I will have a look into it.
Regards,
The simplest you can do is to look at the mass and resistance in a small radius and short tube. The acoustic impedance is fairly simple at low frequencies and you can draw a two component lumped circuit for it. A perforated plate is essentially a lot of such tubes, and if they are separated enough so they do not interact much, the acoustic impedance of the perforation can be found by considering the number of tubes and the perforation rate. From here it is about hole interaction, end effects, and effects coming from the boundary layer being smaller and smaller at higher frequencies.
René (PhD in microacoustics)
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