Abstract
The active control of tonal noise propagating in ducts at
frequencies where many modes are able to propagate is considered.
The final objective of the work reported is to cancel the
prominent 450-500 Hz blade passing frequency of the rotary suction
fans found in chimney stacks of power stations. Three sets of
experimental results are presented and supported by results from
computer simulations. Thus, a number of observations and
guidelines for the design of such a control system that so far
have been drawn only from theory and simulation studies are
discussed based on experimental results from laboratory. The study
of the full control system, which comprises thirty secondary
sources and thirty-two error sensors, has revealed a number of new
results, in particular with respect to the positioning of the
sources and sensors along the length of the duct. Eventually, a
reduction of the radiated power of between 20 and 50 dB was
obtained under laboratory conditions at frequencies where up to
twenty-five modes were able to propagate. The final experiments
carried out in an out-of-use chimney stack showed slightly poorer
results and a number of explanations for this discrepancy are
discussed.
Original language | English |
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Journal | Journal of Sound and Vibration |
Volume | 195 |
Issue number | 1 |
Pages (from-to) | 33-56 |
ISSN | 0022-460X |
DOIs | |
Publication status | Published - 1996 |