A new face drilling rig for narrow tunnels and ... - Advanced Mining

Issue 04 | 2010
TRANSFER OF TECHNOLOGY
Acoustic emission of belt conveyor systems
and stockyard equipment used to handle
bulk goods, its advanced calculation and
noise reduction measures
The increasing capacity of material handling plants, going hand in hand with the spatial approach of settled
areas to industrial zones, inevitably leads to the residents’ demand for the reduction of noise pollution.
That is a challenge to be taken up by both the operator and the manufacturer of plants like that. It means that
those involved have to realize the conceptual characteristics and the physical contents associated with them.
Moreover, it is necessary to become intensively familiar with sound-specific levels and their order of magnitude,
to be capable of taking a view of demands with respect to emissions. Sine a theoretical advanced calculation
alone is not sufficient the manufacturers must acoustically measure plants they already built, in order to detect
the absolute sound levels, and to enable the efficiency of different noise control measures to be analyzed.
Sound
Sound is a mechanical vibration in gases, fluids and
solids. These vibrations propagate at a speed that is specific
to the respective medium, the speed of sound. It concludes
from this that the sound, in contrast to electromagnetic
waves, requires a carrier medium to be propagated.
Sound waves with purely harmonic motion are called
tone. If the sound is composed of several tones, ideally
of the integral multiple of a basic frequency, there will
be talk of harmonic sound. A mix of many frequencies
within a frequency band is called noise (e.g. white or pink
noise). If humans find the presence of sound a nuisance, a
disturbance or even damage, there will be talk of noise.
Fig. 1:
Emission point and Immission place
The Problem
by Dipl.-Ing. Rainer Wirtz
ThyssenKrupp Fördertechnik - BU Materials Handling
St. Ingbert | Germany
The problem can be described, as follows. A machine
makes noises. The noise source is also called place or point
of emission. The noise is transmitted on the transmission
path from the emission point to the immission place, where
certain sound pressure levels must not be exceeded for
reasons whatever they are called.
Sound pressure p
Sound pressure p is the compression load that
is superposed on the atmospheric pressure during
propagation of the sound wave. It is, as effective pressure,
expressed in N/m². The so-called airborne sound is a
transient pressure that is superposed on the relative, static
air pressure. This transient pressure is propagated in the
form of longitudinal waves. Because of the wave character
it comes to reflections, diffraction- and interference
phenomena. The sound pressure is a field size and, as
force, it is defined per unit of area.
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