Development of Adaptive Acoustic Impedance Control Technologies of Acoustic Duct Liner

<table>Fan noise spectra emitted from duct liner II of AAC technology III model and emitted from hard wall duct. Fan rotational speed 6000 rpm; acoustic measuring point 60 deg.</table>

Advances in Acoustics and Vibration

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Figure 16

Figure 16: Development of Adaptive Acoustic Impedance Control Technologies of Acoustic Duct Liner 