Optimal and Adaptive Virtual Unidirectional Sound Source in 
                        Active Noise Control

<table>Noise N1
(broadband noise 200–300 Hz) attenuation. —
Spectrum with ANC, - - - spectrum
without ANC.</table>

Advances in Acoustics and Vibration

Figure 12: Optimal and Adaptive Virtual Unidirectional Sound Source in 
                        Active Noise Control 