Martin Audio Wavefront W8CT, Инструкция по применению

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Point Sources
The effects of geometric spreading are well known for the three idealised sound
sources; the point, line and plane. The behaviour of each is based solely on the
assumption that, in a homogeneous medium, sound propagation from a single point
source is purely spherical. Thus the sound energy in any particular direction is
inversely proportional to the increasing surface area of the sphere. If SWL represents
the continuous sound power output of the source measured at 1 metre, then at a
distance of r metres (where r must always be divided by the measurement distance,
which is usually 1m), the sound pressure level becomes;
SPL = SWL(point) - 10log (4
π
r²)
and I = W / (4
π
r²)
This is can be rewritten simply as;
SPL = SWL(point) - 20log (r) - 11
which is known as the standard
inverse square law for point sources.
For a point source it represents a 6dB reduction in sound pressure level
per doubling of distance.
If the ground is quite hard and reflective, compensation must be made for these
ground reflections. In this case 11 is replaced by 8dB.
Line Sources (e.g. line array loudspeakers)
Classic line and plane sources can then be considered to consist of an infinite number
of evenly distributed individual point sources. The overall behaviour is then found by
integrating the individual effects of each point source over the full length or area. In
the case of an ideal line of infinite length, the results approximate that of purely
cylindrical propagation. Thus the sound energy in any perpendicular direction is
inversely proportional to the increasing circumference of the cylinder. Using the same
nomenclature as above, the sound pressure level becomes;
All material © 2007. Martin Audio Ltd. Subject to change without notice.