Noise power (dB): This is the noise power at source position in decibels.
Airport options: We have two options: An aircraft landing/taking off at 300m or Daily average (number of airport operations in a day).
Solid angle for the propagation (pi): It’s the solid angle for the sphere and it is used in the ISO 9613 model. This value depends on the position of the source. If the source it is the air the value is 4 (sphere complete), if the source is on the ground the value is 2 (semi-sphere).