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Active Noise Control — Tortoise or Dead Parrot

The recent “Active 2002” – International Symposium on Active Noise and Vibration Control, held at Southampton University, attracted over 150 delegates from 28 countries. 120 papers were presented. This is very encouraging. The host country might be expected to have the largest number of delegates. Indeed, there were about 20 UK delegates, although half were from Southampton University itself. About five were from clearly identifiable UK industrial organisations. Similarly, considering the papers presented, the vast majority came from university academics or researchers. Only a few were offered by industrial organisations. These figures may be an indication of the health of active control, which has been in its modern digital phase for about 20 years. But despite the emphasis on digital systems, the most successful product, active headsets, is almost exclusively analogue. There is a great deal of ongoing activity, much research and new researchers coming to the topic, although the range of commercial products – headsets, air-conditioning duct silencers, aircraft interior systems and research controllers – remains disappointingly narrow. Much of active control stays rooted in academic research. It is good and stimulating work, but not yet applicable outside the laboratory. There is a delay of 10 years or more between researchers beginning to lose interest in a topic, having exhausted its possibilities for them, and the time when a product makes its first hesitant appearance. The marketing specialists then have a tremendous hurdle to overcome – the resistance to new technologies when these are more expensive than existing ones. The best active control has managed to do is to stumble along. The promise of 15–20 years ago has not been realised. Admittedly, expectations were over hyped and the customer still looks for the magic, cureall black box. Active control was once presented as a beautiful bird of paradise, ready to take to the air. Is it now a dead parrot? Of course not. A closer analogy is to the tortoise of the fables, whose persistence eventually wins through!