Directional Mics

Manipulate[
 Show[{
   Table[PolarPlot[
     {
      2 r Abs[a (1 + Cos[\[Theta]])],
      2 r Abs[(1 - a) (1 + Cos[\[Theta] + Pi])],
      2 r Abs[a (1 + Cos[\[Theta]])] +
       2 r Abs[(1 - a) (1 + Cos[\[Theta] + Pi])]

      }
     , {\[Theta], 0, 2 Pi}, Axes -> None, PlotRange -> 0.5,
     PlotStyle -> {Directive[Opacity[1 - r], Red],
       Directive[Opacity[1 - r], Blue],
       Directive[Thick, Opacity[1 - r], Purple]}], {r, 0, 1, 0.1}]
   ,
   Graphics[{

     }]
   }
  ]
 , {a, 0, 1}]