Features of the KA450 sound field

Three types of sound field are defined in the above-mentioned standards:

1. Free sound field

2. Diffuse sound field

3. Quasi-free sound field

The quasi-free sound field was defined because it will not always be possible to meet the requirements for a free or diffuse sound field in practice. The requirements for the quasi-free sound field are therefore used as a basis below:

Loudspeaker at the patient's head height

□ Reference axis runs through reference point (= patient's head)

□ Distance between reference point and loudspeaker ≥ 1m

Open

□ Deviation of the sound pressure level at a distance of 0.15 m from the reference point right / left / top / bottom ≤ ± 2 dB for all test signals
(above / below means "above the head" or "below the head")

□ Difference in sound pressure level between front and rear at a distance of 0.10 m from the reference point ≤ ± 1 dB for all test signals in relation to the theoretical values according to the inverse distance law:

(for practical help with the calculation, see e.g. http://www.sengpielaudio.com/Rechner-abstandsgesetz.htm )