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Sampling is elementary. Since we have defined the admittance
as the nominal transfer function, corresponding to
defining the input as driving force and the output as resulting
velocity (see Fig.L.3), we have that
is defined
as the system impulse response
.R.2 We are therefore digitizing a linear
system by sampling its impulse response. The model is then
implemented as a Finite Impulse Response (FIR) digital filter
(§1.5.4). The next subsection describes
the impulse-invariant method for digital filter design which
derives an infinite impulse response (IIR) digital filter that
matches the analog filter impulse response at the sampling points.
Sampling the impulse response has the advantage of preserving resonant frequencies (see next section), but its big disadvantage is aliasing of the frequency response. No ``system'' is truly bandlimited. For example, even a simple