| 摘要 |
PURPOSE:To improve the efficiency of noise reduction on a band-division basis, by compressing and expanding levels by controlling variable filters by divided frequencies. CONSTITUTION:An input signal arriving from a terminal 26 via a high-band passing type variable filter 27 is supplied to adding circuits 28 and 30; and it is added by the adding circuit 28 to the input signal arriving directly and the sum is supplied to a low-band passing type variable filter 29 at the next stage. The output of an adder 30 is divided into two by high-pass filter 31 and low-pass filter 32 in terms of band, and both the variable filters 28 and 29 are controlled by control signals consisting of split components of the input signals extracted from both the filters 31 and 32. Thus, the level-compressed input signal is transmitted from a terminal 35 and supplied to an adder and subtracter 38 via a terminal 37. In a step of processing inverse of the level compression, level expansion complementary to compression characteristics is carried out. Thus, the efficiency of noise reduction is improved. |
