ffeq - creates a band-limited free-field eq inverse filter.
The following artifacts may exist:
1) phase distortion due to neglecting the minphase all-pass component
2) low frequency errors due to small rceps() vectors
3) time-domain aliasing due to inverse filter
4) time-domain aliasing due to band-limiting
1: In constructing the inverse filter using minimum-phase decomposition,
the all-pass component is ignored (allowing phase distortion
in the inverse filter). The result of this can be seen when the inverse
filter is applied to the original system measurement and the minphase
version (see phase (ideal = flat) and impulse response (ideal =
impulse)).
2: When using rceps() to compute minimum-phase, small vectors can
yield artifacts in the low frequencies. Zero-padding reduces these
artifacts. To see this, reduce the padding in the code.
3: Since the inverse filter impulse response is a decaying exponential,
the IR will time-domain alias when taking the IFFT. A long inverse
filter can greatly reduce this artifact.
4: The algorithm used for band-limiting, ffbl(), introduces rect/sinc-like
time-domain aliasing. A long inverse filter can greatly reduce this
artifact.