add: Zotter, et al., diffuse field radius

[joslloand]

Diffuse Sound Field Synthesis

"... approximate radial limit of an error-free sweet area...", eq. 65

// return diffuse field radius from decoding radius
~diffRadius = { |decRadius = (AtkHoa.refRadius), order = (AtkHoa.defaultOrder)|
    order / (order + 1) * decRadius
}

Classes:

• HoaRadius?
• HoaOrder

Method name(s)?:

• diffRadius
• diffuseRadius
• radiusOfDiffuse

[joslloand]

HoaRadius is concerned with the effective soundfield resynthesis radius, so it may not be suitable to include a method here, as we may run the risk of confusing the radius of exact reproduction with the diffuse field synthesis radius.

HoaOrder is likely the ideal class, as we could also include(?):

• -decRadius
• -decodingRadius
• -arrayRadius
• -radiusOfArray

a method returning the target array size given a desired diffuse field radius.

NOTE: this could be used in conjunction with HoaRadius to match a given desired effective radius.

// return decoding radius from diffuse field radius
~decRadius = { |diffRadius = (AtkHoa.refRadius), order = (AtkHoa.defaultOrder)|
        (order + 1) / order * diffRadius
}

[joslloand]

... for naming, review ATK Code Style Guidelines