The Spectrum of the Output of a System

The spectrum of the output of a system is the product of the spectrum of the input and the frequency response of the system. This realization leads naturally to the idea of filtering, or of separating signals based on their frequency content. High-pass, low-pass, and bandpass filters are described.

[BoZhaoengineering]

thank you for your clear interpretation. This happens in mechanical engineering, when we want to know the component/structure reaction from forced vibration. We need determine the H(f) of the designed component and fourier transform vibration from time domain to frequency domain. Other example is earthquake resistance design, we want to know the reaction of structure from seismic action and there are two filters, one is the geotech below the structure and the other is the structure itself. A powerful characteristic description this method is.