Sonic Booms and the Doppler Effect

vs = 1; \[Lambda] = 25; 

dots[t_, vx_] := Flatten[Table[{vx*tt + (vs*(t - tt))*Cos[arg], 
    (vs*(t - tt))*Sin[arg]}, {tt, 0, t, vs*\[Lambda]}, 
    {arg, 0, 2*Pi, 0.1}], 1]
    (* To scale the SmoothDensityHistogram colors, use arg step 
    size .5/(t -tt/1.1) instead of 0.1 *)
    
wavefront[t_, vx_] := Graphics[{{Purple, Thick, 
    Table[Circle[{vx*tt, 0}, vs*(t - tt)], 
    {tt, 0, t, vs*\[Lambda]}]}, {Orange, Disk[{vx*t, 0}, 3]}}, 
    PlotRange -> {{-50, 150}, {-100, 100}}, Axes -> False]
    
pressure[t_, vx_] := Show[
    SmoothDensityHistogram[dots[t, vx], 
    ColorFunction -> "FuchsiaTones", 
    Mesh -> 0, Frame -> False, MaxRecursion -> 5, 
    PlotRange -> {{-50, 150}, {-100, 100}}, Axes -> False], 
    Graphics[{Orange, Disk[{vx*t, 0}, 3]}]]
    
Manipulate[GraphicsRow[{wavefront[t, vx], pressure[t, vx]}, 
    Spacings -> 0.1, Frame -> All, 
    FrameStyle -> White, Background -> Black], 
    {{t, 58}, 1, 101}, {vx, 0, 1.4}]