Radiated pressure from ideal quadrupole:

• Fluid is air at ambiant conditions  (c=344 m/s)
• Frequency is 500 Hz
• Source diameter is 8 cm; sources at (x,y)=(0,0), (0.1,0), (0,0.1), and (0.1,0.1)
• Quadrupole moment (kd)^2=0.81
• Maximum pressure is blue, and minimum (negative) pressure is red, zero pressure is blue/green (the B&K color!)

The movie was created using MATLAB (Registered Trademark).