22 Evaluation of Microphone Density for Finite Element Source Inversion Simulation of a Laboratory Acoustic Test 239 Fig. 22.10 (a) MAC of the pressure magnitude shape for the various target node sets, as a function of frequency. (b) MAC of the real part of pressure shape Fig. 22.11 Sensor wavelength density as a function of frequency for the various target node counts more target nodes are required for the source inversion routine to provide an acoustic field similar to the truth field at nontarget locations. To explore this apparent frequency dependence in a slightly different way, the pressure MAC was plotted not against frequency, but instead against what here is called sensor wavelength density. Sensor wavelength density is the number of target nodes in the inverse simulation, per cubic wavelength. Equation 22.2 shows the sensor wavelength density calculation. Figure 22.11 demonstrates the expression. At low frequency when wavelengths are large, the number of target nodes per cubic wavelength is high. As frequency increases, the wavelengths become shorter and the density decreases. SensorWavelength Density D #target nodes Volume 3 : (22.2)
RkJQdWJsaXNoZXIy MTMzNzEzMQ==