Dispersion calculation for noise according to the
Guidelines ISO 9613-2 (VDI 2714), VDI 2571, VDI 2720, RLS-90 and SCHALL 03
ISO 9613: Acoustics - Attenuation of sound during propagation
Part 2: General method of calculation
The ISO 1996 series of standards specifies methods for the description
of noise outdoors in community environments. Other standards, on the other
hand, specify methods of determining the sound power levels emitted by various
noise sources, such as machinery and specified equipment (ISO 3740 series) or
industrial plants (ISO 897). This part of ISO 9613 is intended to bridge the
gap between these two types of standard, to enable noise levels in the
community to be predicted from sources of known sound emissions. This method
described in this part of ISO 9613 is general in the sense that it may be
applied to a wide variety of noise sources, and covers most of the major
mechanisms of attenuation. There are, however, constraints on its use, which
arise principally from the description of environmental noise in the ISO 1996
series of standards.
This part of ISO 9613 specifies an engineering method for calculating
the attenuation of sound during propagation outdoors in order to predict the
levels of environmental noise at a distance from a variety of sources. The
method predicts the equivalent continuous A-weighted sound pressure level (as
described in parts 1 to 3 of ISO 1996) under meteorological conditions
favorable to propagation from sources of known sound emission.
These conditions are for downwind propagation, as specified in 18.104.22.168
of ISO 1996-2:1987 or, equivalently, propagation under a well-developed
moderate ground-based temperature inversion, such as commonly occurs at night.
Inversion conditions over water surfaces are not covered and may result in
higher sound pressure levels than predicted from this part of ISO 9613.
The method also predicts a long-term average A-weighted sound pressure
level as specified in ISO 1996-1 and ISO 1996-2. The long-term average
A-weighted sound pressure level encompasses levels for a wide variety of
The method specified in this part of ISO 9613 consists specifically of
octave-band algorithms (with nominal midband frequencies from 63 Hz to 8 kHz)
for calculating the attenuation of sound which originates from a point sound
source, or an assembly of point sources. The source (or sources) may be moving
or stationary. Specific terms are provided in the algorithms for the following
- geometrical divergence:
- atmospheric absorption;
- ground effect
- reflection from surfaces
- screening by obstacles
Additional information concerning propagation through housing, foliage
and industrial sites is given in annex A.
This method is applicable in practice to a great variety of noise
sources and environments. It is applicable, directly or indirectly, to most
situations concerning road or rail traffic, industrial noise sources,
construction activities, and many other ground-based noise sources. It does not
apply to sound from aircraft in flight, or to blast waves from mining, military
or similar operations.
To apply the method of this part of ISO 9613, several parameters need to
be known with respect to the geometry of the source and of the environment, the
ground surface characteristics, and the source strength in terms of octave-band
sound power levels for directions relevant to the propagation.
NOTE1 If only A-weighted sound power levels of the sources are known,
the attenuation terms for 500 Hz may be used to estimate the resulting
The accuracy of the method and the limitations to its use in practice
are described in clause 9.