Patent ID: 7890323

Claim:
A digital filtering method for extracting a feature quantity based on an inputted signal waveform, the method comprising: a step of inputting a signal waveform as an input signal, quantizing the signal waveform to acquire a quantized data, and storing such quantized data in a storage device; a step, in said quantized data, of pre-establishing as a summation region a prescribed region adjoining a selected point and/or pre-establishing the number of data contained in the summation region, so that i) a summation value is obtained, at each individual point in the quantized data stored in said storage device, by summing all data values in the summation region; ii) a division value is obtained by dividing said summation value by the number of data in the summation region; and iii) a difference is calculated as a subtraction value through subtraction between the data value in the quantized data at said point and said division value; whereby said division value and subtraction value are outputted; and a step of effecting a digital filtering by repeating said steps to calculate said division value and subtraction value in each individual quantized data, so that the inputted signal waveform is subjected to the digital filtering based on each division value and subtraction value which are individually outputted, the step of effecting said digital filtering comprising: a step of effecting a high-pass filtering based on said subtraction value; and a step of effecting a low-pass filtering based on said division value wherein the number of data to be summed in the prescribed region is a power of two.