How the law attempts to deal with hoaxes and pranks in the media that lead to harm

Today I can’t avoid talking about how the law attempts to deal with hoaxes and pranks in the media that lead to harm, following the shocking outcome of the prank by Mel Greig and Michael Christian, hosts of 2Day FM Radio station in Sydney

Notes for RNZ slot from Ursula Cheer (Associate Professor) Canterbury University, 12 October 2011

Ursula Cheer, Associate Professor of Law at the University of Canterbury, discusses the recent Rio Ferdinand decision, a privacy case from the High Court in the UK

Structural-acoustic coupling and psychophysical effects in the active control of noise in vehicles

Active noise control systems offer a potential method of reducing the weight of passive acoustic treatment and, therefore, increasing vehicles' fuel efficiency. These can be particularly cost-efficient if integrated with the entertainment system. A combined system is presented employing feedforward control of engine noise and feedback control of road noise, using a `modal' error signal. Due to the dependence of the feedback system on the modal response of the vehicle cabin, the influence of structural-acoustic coupling on this response and the consequent effects on the control performance are investigated. Simulations of the performance of the control systems in rigid and non-rigid enclosures show that the feedforward component is largely unaffected by structural-acoustic coupling, whilst the modal feedback performance is reduced by 3 dB due to the shift in the frequency of the targeted acoustic mode. The simulation results are confirmed through experiments conducted in a structural-acoustic coupled enclosure

Active structural acoustic control using the remote sensor method

Active structural acoustic control (ASAC) is an effective method of reducing the sound radiation from vibrating structures. In order to implement ASAC systems using only structural actuators and sensors, it is necessary to employ a model of the sound radiation from the structure. Such models have been presented in the literature for simple structures, such as baffled rectangular plates, and methods of determining the radiation modes of more complex practical structures using experimental data have also been explored. A similar problem arises in the context of active noise control, where cancellation of a disturbance is required at positions in space where it is not possible to locate a physical error microphone. In this case the signals at the cancellation points can be estimated from the outputs of remotely located measurement sensors using the “remote microphone method”. This remote microphone method is extended here to the ASAC problem, in which the pressures at a number of microphone locations must be estimated from measurements on the structure of the radiating system. The control and estimation strategies are described and the performance is assessed for a typical structural radiation problem

Design and implementation of a personal audio system in a car cabin

The generation of personal listening zones in a car cabin would allow the different occupants to listen to different audio programmes without the use of headphones. This would allow, for example, the driver to listen to a navigation system whilst the rear passengers watched a film. Personal audio systems have previously been implemented in mobile devices and monitors, for example, however, the investigation of the effects of an enclosure on the generation of personal listening zones has been limited. This paper presents an investigation of the effects of a car cabin sized enclosure on the generation of independent listening zones in the front and rear seats. The standard car audio loudspeaker array is used to produce independent listening zones at low frequencies, while a second array of small loudspeakers positioned at the four headrest positions is used to provide control over the rest of the audio bandwidth. The proposed arrays are implemented in a real car and the results of a real-time implementation are presented.<br/

More on suppression and the internet in New Zealand

Ursula Cheer brings the reader up-to-date to her article on the decision of the judge in New Zealand Police v KOr

An investigation of delayless subband adaptive filtering for multi-input multi-output active noise control applications

The broadband control of noise and vibration using multi-input, multi-output (MIMO) active control systems has a potentially wide variety of applications. However, the performance of MIMO systems is often limited in practice by high computational demand and slow convergence speeds. In the somewhat simpler context of single-input, single- output broadband control, these problems have been overcome through a variety of methods including subband adaptive filtering. This paper presents an extension of the subband adaptive filtering technique to the MIMO active control problem and presents a comprehensive study of both the computational requirements and control performance. The implementation of the MIMO filtered-x LMS algorithm using subband adaptive filtering is described and the details of two specific implementations are presented. The computational demands of the two MIMO subband active control algorithms are then compared to that of the standard full-band algorithm. This comparison shows that as the number of subbands employed in the subband algorithms is increased, the computational demand is significantly reduced compared to the full-band implementation provided that a restructured analysis filter-bank is employed. An analysis of the convergence of the MIMO subband adaptive algorithm is then presented and this demonstrates that although the convergence of the control filter coefficients is dependent on the eigenvalue spread of the subband Hessian matrix, which reduces as the number of subbands is increased, the convergence of the cost function is limited for large numbers of subbands due to the simultaneous increase in the weight stacking distortion. The performance of the two MIMO subband algorithms and the standard full-band algorithm has then been assessed through a series of time-domain simulations of a practical active control system and it has been shown that the subband algorithms are able to achieve a significant increase in the convergence speed compared to the full-band implementatio

Comparison of adaptive algorithms for the control of tonal disturbances in mechanical systems

This paper presents a study on the performance of adaptive control algorithms designed to reduce the vibration of mechanical systems excited by a harmonic disturbance. The mechanical system consists of a mass suspended on a spring and a damper. The system is equipped with a force actuator in parallel with the suspension. The control signal driving the actuator is generated by adjusting the amplitude and phase of a sinusoidal reference signal at the same frequency as the excitation. An adaptive feedforward control algorithm is used to adapt the amplitude and phase of the control signal, to minimise the mean square velocity of the mass. Two adaptation strategies are considered in which the control signal is either updated after each period of the oscillation or at every time sample. The first strategy is traditionally used in vibration control in helicopters for example; the second strategy is normally referred to as the filtered-x least mean square algorithm and is often used to control engine noise in cars. The two adaptation strategies are compared through a parametric study, which investigates the influence of the properties of both the mechanical system and the control system on the convergence speed of the two algorithms