Environmental Assessment
Volume B-3.5
Mine
Noise
Ambatovy Project
71
January 2006
The impact magnitudes determined using Figure 3.5-1 range from negligible to
low at all community receptors. The World Bank nighttime noise criteria will be
met at all communities, although background noise levels in Behontsa and
Berano are predicted to increase. The resulting residual impacts range from
negligible to low and are summarized in Table 3.5-6.
Table 3.5-6 Residual Impact Classification - Noise
Community Direction
Magnitude
Geographic Extent
Duration
Reversibility
Frequency
Environmental
Consequence
Behontsa
negative
:
an increase
in noise
levels
negligible
: no
noticeable increase in
background noise
levels; all noise below
World Bank criteria
local
: at specific
community receptors
according to World
Bank criteria
medium-term
:
3 to 30 years
reversible
noise is stopped
once project
activity stops
high
:
occurs
continuously
negligible
Berano
negative
:
an increase
in noise
levels
low
: background noise
levels increased by over
3 dBA all noise below
World Bank criteria
local
: at specific
community receptors
according to World
Bank criteria
medium-term
:
3 to 30 years
reversible
noise is stopped
once project
activity stops
high
:
occurs
continuously
low
Sahamalotra
negative
:
an increase
in noise
levels
negligible
: no
noticeable increase in
background noise
levels; all noise below
World Bank criteria
local
: at specific
community receptors
according to World
Bank criteria
medium-term
:
3 to 30 years
reversible
noise is stopped
once project
activity stops
high
:
occurs
continuously
negligible
3.5.4.8 Prediction Confidence
The modelling of outdoor noise attenuation is conducted using standard
algorithms and assumptions that tend to simplify the acoustic environment.
Noise, whether natural or man-made, is normally variable over time. The
algorithms and the L
eq
indicator account for that variability, but do not predict it.
The variation of noise sources over time can be addressed in the CadnaA model
in many ways, depending on the noise source being assessed and the level of
detail required.
The quality and relevance of predictions from the noise model is dependant on
the data inputs. For the assessment, noise sources were established with actual
field measurement or vendor sound emission data where possible to ensure the
accuracy of sources. Modelled noise levels for the existing activity on the site
were compared with background noise data to ensure the simulations were
representative of the site.
The CadnaA model was designed to predict outdoor noise in accordance with
International Standards Organization (ISO) 9613 (1&2):
Attenuation of Sound
During Propagation Outdoors
(ISO 9613) as well as several international and
European acoustic standards. The ISO 9613 method will predict noise
