| 摘要 |
PURPOSE:To reduce a noise generated in a propagation passage of an acoustic wave by updating successively a filter coefficient of an adaptive type FIR(Finite Impulse Response) filter, based on a detected low sound decrease level. CONSTITUTION:The device is provided with a changing means 16 for changing a value of a step size parameter of a control means 15, based on a low sound decreasing signal detected by a monitor microphone. In such a state, in a step 3, an error e(k) of a noise d(k) and an inversion sound signal y(k) is calculated, and when its square average value mse(k) is above a set value (msemin) (mse(k) >=msemin), an initial value mu max is used as a step size parameter mu in an operation expression of a filter coefficient W(k) of an adaptive type FIR filter in a step 6, and at the time of msc(k) < msemin, it is changed to the minimum value mu min in a step 8. Accordingly, the filter coefficient W is updated quickly toward a correct value in the beginning, and when it becomes adjacent to the correct value, it is updated gradually and goes toward the correct value. |
