Combined feedback-feedforward active noise-reducing headset--the effect of the acoustics on broadband performance

Active noise-reducing headsets that employ analog feedback control and provide good broadband attenuation are commercially available for a wide range of applications. Recent studies have explored the integration of an adaptive digital feedforward controller with the analog feedback controller to provide additional attenuation of periodic noise components. This paper presents an experimental study of such a combined control system, but with both feedback- and feedforward controllers attenuating broadband noise. Good performance is demonstrated in a reverberant sound field, while under direct sound-field conditions the attenuation performance of the feedforward controller is shown to be dependent on head position. The paper concludes with an analysis of the forward path delay showing how the passive attenuation mechanism improves broadband performance.