it resembles what we learned from the radiation characteristics of
a multiple sphere when we observe a sound at central line when the zie equal zero.
Radiation characteristics baffled piston at the centre line,
depending on where we observe the sound,
compare with radiator sound size which can be represented by kz,
the radiation characteristics of baffled piston.
This really follows in the far field the monopole radiation.
Okay, because the piston is radiating like
this and if you think about the L particle over here,
L particle over here will not
move in this direction because to satisfy the boundary condition over
here baffled piston meaning that there is no flow fluid oscillation in this direction.
Therefore the radiation in this axis,
along this axis would be very
very different with the characteristics of radiation in this axis.
Therefore there is a directivity pattern
depending on the size as well as the observation points.