Patent ID: 7136605

Claim:
An image forming apparatus that forms an image onto a recording medium, wherein a discomfort index S calculated from an equation S=A ×(loudness value)+ B ×(sharpness value)+ C ×(tonality value)+ D ×(impulsiveness value)+ E where 0.213845≦A≦0.255694, 0.325852≦B≦0.443631, 2.049496≦C≦3.207187, 1.427895≦D≦1.708411, and −4.224266≦E≦−3.356324, using loudness, sharpness, tonality, and impulsiveness of a psycho-acoustic parameter obtained from a sound generated from the image forming apparatus when forming an image onto the recording medium satisfies an inequality S≦0.5664Ln(ppm)-2.1364 where 14≦ppm≦38 Ln indicates natural log, and ppm is an output number of the recording medium per minute with A4 size in horizontal direction, wherein the sound is collected at a listening position approximately one meter from an edge of the image forming apparatus.