Patent ID: 8885848

Claim:
A quality evaluation method, comprising: obtaining operation sound of conforming product samples as conforming-product sound information, the conforming product samples being products of the same kind as a subject workpiece to be evaluated for quality; digitizing the conforming-product sound information of the conforming product samples to obtain conforming-product sound evaluation amounts on a time-series basis, using at least one psychoacoustic parameter; determining an evaluation threshold preset in an apparatus using sound evaluation amounts each obtained by adding a result of a multiplication of a standard deviation of a corresponding one of the conforming-product sound evaluation amounts, a random coefficient λX, and a normal random number to one conforming-product sound evaluation amount randomly selected from among the conforming-product sound evaluation amounts, the random coefficient λX being equal to or larger than 0, the normal random number being distributed at an average of 0 and a standard deviation of 1, and the selected one conforming-product sound evaluation amount being allowed to be repeatedly selected; obtaining operation sound emitted from the subject workpiece as subject sound information; digitizing the subject sound information of the subject workpiece to obtain a subject sound evaluation amount on a time-series basis; and evaluating quality of the subject workpiece based on a result of comparison of the subject sound evaluation amount of the subject workpiece with the determined evaluation threshold.