The zone of local control around a "virtual energy density sensor" is compared with that offered by an actual energy density sensor, a single microphone, and a virtual microphone. Intended as an introduction to the concept of forward difference prediction and a precursor to evaluating the virtual sensor control algorithms in damped enclosures, this paper investigates an idealized scenario of a single primary sound source in a free-field environment. An analytical model is used to predict the performance of the virtual error sensors and compare their control performance with their physical counterparts. The model is then experimentally validated. The model shows that in general the virtual energy density sensor outperforms the actual energy density sensor, the actual microphone, and the virtual microphone in terms of centering a practically sized zone of local control around an observer who is remotely located from any physical sensors. However, in practice, the virtual sensor algorithms are shown to be sensitive (by varying degrees) to short wavelength spatial pressure variations of the primary and secondary sound fields.

Virtual error sensing is a novel active noise control technique, which is designed to produce a zone of attenuation remote from the physical error sensors. In this letter virtual sensing is investigated for tonal noise (both on and off resonance) in a long narrow duct. The performance of the virtual error sensors using real-time control is compared to the performance determined from an analytical model and the performance determined through the postprocessing of experimental data. Two examples of control using postprocessed experimental transfer function data are presented; the first relied on transfer functions measured using broadband noise and the second relied on transfer functions measured at discrete frequencies. The results highlight the significant errors encountered as a result of using broadband transfer functions in lightly damped enclosures.

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There is increasing evidence that the cost of our 'disposable society' is beginning to take a toll and that the continued use of unsustainable resources will have a severe detrimental affect upon the living standards of our successive generations. The possibility of our fossil-fuel resources running dry becomes more likely as the global demand for power increases. This particular resource is also directly responsible for releasing copious quantities of previously entombed carbon directly into our atmosphere, possibly causing global warming. Quite obviously there is therefore a need to consider other means of energy generation that reduce our rate of consuming this finite resource, while also reducing the potential for damage to our planet. This is by no means a new concept, but while scientists and engineers have the ability to initiate change through design, there does not seem to be the level of urgency required to implement effective action. Perhaps there is public confusion regarding alternative energy sources, or perhaps there is simply not sufficient widespread concern for something dramatic to happen right now. As this paper will show, engineering education can be the starting point for change. Graduate engineers can lead the way by researching, designing and developing new practical alternative fuel applications if they are sufficiently enthusiastic. These same engineers can also improve the public's understanding of alternative energy applications. A number of problem based learning projects have therefore been introduced at The University of Adelaide to develop the necessary graduate attributes while also developing a passion for the development of alternative energy solutions. The merits and outcomes of two projects are discussed here: The Biodiesel Motorbike Project and The Hybrid Electric-Solar Car Project.