ACTIVE CONTROL OF THE TRANSMISSION OF SOUND THROUGH A THIN CYLINDRICAL-SHELL .2. THE MINIMIZATION OF ACOUSTIC POTENTIAL-ENERGY

By using the model of an aircraft fuselage discussed in Part I, an analysis is presented which demonstrates that the total acoustic potential energy (Ep) within the cylindrical model is minimized by a unique vector of secondary force inputs. Similar analysis is used to derive an expression for the optimum vector of secondary forces that minimize the sum of the squared pressures at a number of microphone positions (Jp) within the fuselage model. These results are used as the basis of computer simulations in which Ep and Jp are minimized at 88 Hz and 176 Hz. It is shown that large global reductions in the acoustic energy within the cylinder model can be obtained by using very few secondary forces. This is achieved, however, at the cost of increasing the vibrational energy in the cylinder. © 1993 Academic Press Limited.