ABSTRACT
The graphing of the factored-form transfer function, as compared with the polynomial form, helps us understand certain features of system response. The two second-order terms in Eq. (9-38) both have equally light damping, so our earlier experience with individual second-order systems would lead us to believe that their resonance behavior would be equally "bad" in this more complex system. The graphing procedure, however, clearly shows that, once we pass the lowest natural frequency, any higher-frequency resonances will be depressed because their amplitude ratio is plotted "on top of' the -40 db/decade asymptote of the first natural frequency. Thus the first peak is at about +20 db (magnification of 10) but the second is only about -5 db (magnification of 0.56). A curve plotted by the computer, directly from the polynomial transfer function will of course show the correct values of all the peaks, but will not explain why the higher-frequency peaks are small even though they have equally small ~'s.
