| 摘要 |
PROBLEM TO BE SOLVED: To provide a frequency analyzing method and an encoding method for acoustic signal by which a plurality of frequency components can be extracted in a prescribed block, arithmetic load can be suppressed, time resolution can be improved and a hidden sound component can be extracted as well especially when analyzing cardiac sound. SOLUTION: A plurality of main zero crossings, where an original acoustic signal crosses a '0' level, is found (a) and a main zero crossing t1 to become a starting point and a main zero crossing t2 to become an ending point are selected out of the main zero crossings (b) so that a unit block can be set. Then, a main period TA is calculated from the arrangement of the main zero crossings t1 and t2 in the set unit block and a main amplitude A is found from an acoustic signal in the unit block (c). Continuously, a corrected acoustic signal is provided by removing the DC component of the acoustic signal corresponding to an interval between adjacent main zero crossings in the unit block (d) and a plurality of subordinate zero crossings, where this corrected acoustic signal crosses the '0' level, are found (e). Then, a subordinate period T is calculated and a subordinate amplitude A is found from the arrangement of the subordinate zero crossings t3 and t4. |
