When the directional response pattern is highly symmetric about the reference axis, which is commonly the case for directional microphones isolated in a free field, Q can be determined from data obtained only in the horizontal plane at [alpha] = 0[degrees] between the azimuth angles of 0[degrees] and 180[degrees] (11), (12).
As is the case with an actual person, the head, torso and pinna of the manikin affect the directional response pattern and contribute to the asymmetry, as does the hearing aid style (in-the-ear, behind-the-ear, etc.
6] arise from imperfections in setting the elevation angle in combination with imprecise vertical aiming of the directional response pattern.
To show examples of the directional response patterns programmed in the aids used in the interlaboratory comparison and intrinsic to the unaided manikin, polar response patterns measured at NIST in the horizontal plane at [alpha] = 0[degrees] for three of the programmed memories and the unaided manikin are displayed in Fig.
N] measured (seven directional response patterns as a function of seventeen frequency bands).