•LOW frequencies: wavelength longer than array width -
no phase difference
between mikes - local approach provide low spatial resolution (single, large lobe) - global
approach simply fails (the
linear system becomes singular)
•
•MID frequencies: wavelength comparable with array width -with local approach secondary
lobes arise in spherical or plane wave detection (negligible if the total bandwidth
is sufficiently wide) -
the global approach works fine, suppressing
the side lobes, and providing a narrow spot.
•
•HIGH frequencies: wavelength is shorter than twice the average mike
spacing (Nyquist limit) - spatial undersampling - spatial aliasing effects – random disposition of microphones can help the local approach to still provide some meaningful result - the global
approach fails again
•