Environmental Assessment
Volume B-3.5
Mine
Noise
Ambatovy Project
61
January 2006
3.5
NOISE
3.5.1
Introduction
The noise assessment of the Ambatovy Project (the project) provides a complete
impact analysis of the proposed project and identifies the potential effects of
sound emissions associated with the proposed project activities. In this volume
of the Environmental Assessment (EA), project activities associated with the
mine are assessed. Information is provided on existing noise levels in the area as
well as the changes expected to result from the mine.
The focus of the noise assessment is on determining changes to the existing
ambient noise levels due to project operations and comparing the results with
noise guidelines from the World Bank. The assessment is conducted from the
point of view of human response. The effects of noise on wildlife are assessed in
Volume B, Section 4.2. Noise is also an input to the analysis of social effects in
Volume B, Section 5.1.
A few key concepts relating to noise are presented below:
•
“Sound” or “sound emissions” refers to the acoustic energy emitted by
natural or man-made sources, including the project activities.
•
“Noise” or “noise levels” refer to the levels that can be heard by a
person or measured at a receptor.
•
A noise “receptor” is a location where measurements or predictions of
noise levels are made.
•
The “volume” of a sound or noise is expressed on a logarithmic scale, in
units called decibels (dB). Since the scale is logarithmic, a sound or
noise that is twice as loud as another will only be three decibels (3 dB)
higher. A 3 dB change is also the threshold at which a person may be
able to notice a change in volume.
•
Sound emissions and noise levels also have a “frequency”. The human
ear does not respond to all frequencies in the same way. Mid-range
frequencies are most readily detected by the human ear, whereas low
and high frequencies are harder to hear. Environmental noise levels are
usually presented as “A-weighted” decibels (or dBA), which
incorporates the frequency response of the human ear. While low
frequency noise may not be “heard”, it can often be felt.
•
Outdoor noise is usually expressed as an “equivalent noise level” (L
eq
),
which is a logarithmic average of the measured or predicted noise levels
over a given period of time. This is the preferred noise indicator for
