Cutoff frequency, definition

Analog to the piezoelectric transducer, the mechanical behaviour can be described by a spring with the mass m and the stiffness cm. The amplitude response I/Fg of the magnetostrictive transducer has a definite lower cutoff frequency /u and a mechanically determined natural frequency fo for a short-circuit electrical port (Vg = 0), and the amplitude response s/J has a mechanically determined natural frequency fo for an open mechanical port... 

To make further progress, it is standard practice to take this definition of the spectral density and replace it by a continuous form based on physical intuition. A form that is often used for the spectral density is a product of ohmic dissipation qco (which corresponds to Markovian dynamics) times an exponential cutoff (which reflects the fact that frequencies of the normal modes of a finite system have an upper cutoff) ... 

A somewhat arbitrary definition is made for bandwidth. Amplifier cutoff is defined as that frequency (coj at which the power output from the amplifier is one-half of the maximum power, or... 

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