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There is a new method of noise cancellation proposed in this
thesis. The study of adaptive ducts noise cancellation focuses
on the development of electric noise cancelling equipment to
adapt to one-dimension acoustic field such as the ventilative
duct of air condition, the exhaust pipe of engine and the
opening for ventilation of dust-collecting equipment. This new
method is to make use of artificial noise to cancel the
original noisy signal, that is, the active noise cancellation,
which is different from the traditional passive noise control
like the muffler of car or motorcycle. This new method is
effective especially in low frequency. This controller is
designed for the skill of discrete-time signal processing. And
the method of control is devided into two types. The first one
is feedforward control. Before the commence of this type, the
work of system identification must be finished. The second one
is adaptive control, which is to make use of the lest-mean-
square method. From the result of this experiment, it's very
clear to see that by means of the research of controller to
apply these control theories above to the topic of practical
industrial application is very meaningful.
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