Adjust the soundfield directivity of a first order ambisonic signal (B-format) across the origin.
The B-format signal, an array: [w, x, y, z]
The distortion angle, in radians. 0 to pi/2
Output will be multiplied by this value.
This value will be added to the output.
Angle = 0 retains the current directivity of the soundfield. Increasing angle towards pi/2 decreases the directivity, reducing the gains on the directional compenents to zero, and is equivalent to a spatial low-pass filter. The resulting image becomes omnidirectional or directionless.
Please see various examples here.