Apply proximity filtering to a first order ambisonic signal (B-format).
The B-format signal, an array: [w, x, y, z]
The distance, in meters.
WARNING: Distance = 0 is an invalid value!
Output will be multiplied by this value.
This value will be added to the output.
FoaProximity facilitates the introduction of the proximity effect to encoded signals. At extremes, the proximity effect introduces a strong bass boost, as well as phase differences. The proximity effect can be an important contributor to perceptions of nearness.
Please see this.