L-Acoustics V-DOSC - Figure 112: Illustration of Dborder and DV for a Flat 12 Enclosure Array; Table 20: Border (in M) between Cylindrical (Fresnel) and Spherical (Fraunhofer) Zones; Table 21: DV - Vertical Coverage Angle in the Farfield Region

L-ACOUSTICS V-DOSC Manual Version 4 6/29/2005 Page 151 of 158
Table 20: Border (in m) Between Cylindrical (Fresnel) and Spherical (Fraunhofer) Zones
Freq
(Hz)
2 Enclosures
H=0.9 m
d
border
(m)
4 Enclosures
H=1.8 m
d
border
(m)
8 Enclosures
H=3.6 m
d
border
(m)
12 Enclosures
H=5.4m
d
border
(m)
63 No cylindrical No cylindrical No cylindrical 1
125 No cylindrical No cylindrical 2 5
250 No cylindrical 1 5 11
500 0 2 10 22
1k 1 5 19 44
2k 2 10 39 87
4k 5 19 78 175
8k 10 39 156 350
16k 19 78 311 700
Table 21: Dv - Vertical Coverage Angle in the Farfield Region
Freq
(Hz)
2 Enclosures
H=0.9 m
D
v
(deg)
4 Enclosures
H=1.8 m
D
v
(deg)
8 Enclosures
H=3.6 m
D
v
(deg)
12 Enclosures
H=5.4m
D
v
(deg)
63 - - 124 72
125 - 125 53 34
250 125 53 26 17
500 53 26 13 8.5
1k 26 13 6.4 4.2
2k 13 6.4 3.2 2.1
4k 6.4 3.2 1.6 1.1
8k 3.2 1.6 0.8 0.5
16k 1.6 0.8 0.4 0.3
At 1 kHz a flat V-DOSC array of 8 enclosures (H=3.6 m) radiates a wavefront that is cylindrical
over a distance of 19 m. Beyond this distance, the wavefront becomes spherical, and the
coverage angle is 6° (i.e., the wavefront at 1 kHz is defined by the height of the array up to 19m
and broadens by +/-3° starting at d
border
= 19 m). For a person located less than 19m from the
sound source, frequencies below 1kHz are radiated in spherical mode with an attenuation rate
of 6 dB per doubling of distance. All frequencies higher than 1kHz propagate in cylindrical mode
with an attenuation rate of 3 dB per doubling of distance.
Figure 112: Illustration of dborder and Dv for a flat 12 enclosure array