where;
It also can be written in the function of frequency ;
Using spectral method;
In most cases, the system are not purely linear, then the Eq 12 can be expanded to;
Seat Vibration Theoretical Method
Seat Vibration Theoretical Method
Using indenter head as replacement to human subject, dynamic stiffness of seat can be represented by;
= \frac{F_3}{X'_s(\omega)})
where;
 = force\:measured\:at\:the\:indenter )
= displacement\:at\:the\:base\:of\:the\:seat)
= \frac{F_3(\omega)}{-\omega^{-2} A_s(\omega)} = K(\omega) + C(\omega)*i)
It also can be written in the function of frequency ;
= \frac{F_3(f)}{(-2*\pi.f)^{-2} A_s(f)} = K (f) + 2\pi fC(f)*i)
Using spectral method;
 =\frac{G_{xF}(f)}{G_{xx}(f)} = K (f) + 2\pi fC(f)*i)
 = \text{Cross spectral density of input displacement } x(t) \text{ and output dynamic force } F(t))
=Power\:spectral\:density\:of\:input\:displacement )
In most cases, the system are not purely linear, then the Eq 12 can be expanded to;
 =\frac{G_{xF}(f)}{-\omega^{-2}G_{xx}(f)} = K (f) + 2\pi fC(f)*i)
where;
It also can be written in the function of frequency ;
Using spectral method;
In most cases, the system are not purely linear, then the Eq 12 can be expanded to;