Cornelis D. Petersen

A Review of Virtual Sensing Algorithms for Active Noise Control

Traditional local active noise control systems minimise the measured acoustic pres- sure to generate a zone of quiet at the physical error sensor location. The resulting zone of quiet is generally limited in size and this requires the physical error sensor be placed at the desired location of attenuation, which is often inconvenient. To overcome this, a number of virtual sensing algorithms have been developed for active noise control. Using the physical error signal, the control signal and knowledge of the system, these virtual sensing algorithms estimate the error signal at a location that is remote from the physical error sensor, referred to as the virtual location. Instead of minimising the physical error signal, the estimated error sig- nal is minimised with the active noise control system to generate a zone of quiet at the virtual location. This paper will review a number of virtual sensing algorithms developed for active noise control. Additionally, the performance of these virtual sensing algorithms in numerical simulations and in experiments is discussed and compared.

A moving zone of quiet for narrowband noise in a one-dimensional duct using virtual sensing

A frequent problem in active noise control is that the zone of quiet created at the error sensor tends to be very small. This means that the error sensor generally needs to be located close to an observers ear, which might not always be a convenient or feasible solution. Virtual sensing is a method that can move the zone of quiet away from the error sensor to a desired location that is spatially fixed. This method has been investigated previously, and has shown potential to improve the performance of an active noise control system. However, it is very likely that the desired location of the zone of quiet is not spatially fixed. An active noise control system incorporating a virtual sensing method thus has to be able to create a moving zone of quiet that tracks the observers ears. This paper presents a method for creating a moving zone of quiet based on the LMS virtual microphone technique. To illustrate the proposed method, it is implemented in an acoustic duct and narrowband control results are presented. These results show that a moving zone of quiet was effectively created inside the duct for narrowband noise.

Comment on “A Virtual Sensing Method for Tonal ANVC Systems” [C. M. Tran and S. C. Southward, 2002, J. Dyn. Syst., Meas., Control124(1), 35–40]

In a paper by Tran and Southward (2002, J. Dyn. Syst., Meas., Control, 124(1), pp. 35–40), a virtual sensing method for tonal active noise and vibration control systems is proposed. The aim of the proposed method is to obtain accurate estimates of the virtual outputs of the dynamic system under consideration. For this purpose, a hybrid adaptive feedforward observer is designed based on an observable state-space representation of the dynamic system. In this paper, it is shown that if the number of physical sensors used in the proposed method is less than the state-space system order, the observer can converge to infinitely many solutions for which the state reconstruction errors are not equal to zero. Since accurate state estimates are required to obtain accurate estimates of the virtual sensor outputs, the suggested hybrid adaptive feedforward observer is only suitable for rejecting nonstationary disturbances at the physical sensor outputs, and not for virtual sensing purposes.