Development of Adaptive Acoustic Impedance Control Technologies of Acoustic Duct Liner

<table>Effect of acoustic absorbent material on fan noise spectra emitted from duct liner II of AAC technology III model. Fan rotational speed 3000 rpm; acoustic measuring point 60 deg.; with mobile reflective plate; parallel shift; 25 mm position fixed; without tunable perforated plate.</table>

Advances in Acoustics and Vibration

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Figure 19

Figure 19: Development of Adaptive Acoustic Impedance Control Technologies of Acoustic Duct Liner 