DIGITAL FILTER, FILTERING METHOD AND DIGITAL AUDIO PROCESSING CIRCUIT USING THEM, AND ELECTRONIC DEVICE

PROBLEM TO BE SOLVED: To provide a digital filter, a filtering method and a digital audio processing circuit using them, and an electronic device, which can reduce power consumption. SOLUTION: An interpolation filter 20 administers filtering to digital audio signals S4 whose sampling frequencies fs are different. A plurality of delay elements D1-Dn is connected in multistage and delay the audio signal S4 every predetermined time τ. A multiplier 22 multiplies the audio signal delayed by each delay element D by a predetermined coefficient C set for each delay element D. The number of outputs of the delay elements D that are to be a multiplying object of the multiplier 22 are increased or decreased in accordance with a sampling frequency of the audio signal S4. The multiplier uses outputs of all delay elements D as a multiplying object when the sampling frequency fs is under a predetermined threshold value fth, and uses an output/outputs of part of the delay elements D as a multiplying object when it is above the threshold value fth. COPYRIGHT: (C)2008,JPO&INPIT