| 摘要 |
<p>A low-pass filter (1) of over-sampling type over-samples an input digital audio signal T1 and filters and removes the low frequency components of the produced aliasing noise. A spectrum analysis circuit (3) calculates the spectrum strength of a predetermined band of the output signal from the low-pass filter (1). An expansion signal generating circuit (5) generates an expansion signal having higher frequency components from the output signal from the low-pass filter (1). A level control circuit (4) controls the level of the expansion signal according to the output signal from the spectrum analysis circuit (3). An adder (2) adds the level-controlled expansion signal to the output signal from the low-pass filter (1) thereby to generate a digital audio signal T2.</p> |
