•As a complex time-domain waveform can be though as the
sum of a number of sinusoidal
and cosinusoidal functions, so a complex spatial distribution around a given notional point can be expressed as the sum of a
number of spherical harmonic
functions
•When the signals corresponding to spherical harmonics up
to 3° order are summed with
proper gains, one obtains a “virtual microphone” having a directivity pattern which can be very complex and highly
directive