Project: Paralellepipoid Noise Measurement Project
Acoustical Assessment
Client: Construction Contractor - Joint Venture
Location: China
Type of Project: Acoustic Assessment and Noise Measurement
Start: 2004
A major Joint Venture consortium of contractors engaged the services
of Dr. David Green, of as an Accredited Monitoring Professional to
determine sound power levels (SWL) for various powered mechanical
equipment (PME) and prepare a noise assessment report. The use of SWL
measurements provided business value and were used to advantage in the application for construction noise permits for a major drainage construction works contract.
The commencement of several related contracts had successfully
brought the sewerage improvement works for the city forward into the
construction phase. Advanced site preparation work started in February
2004 and construction commenced accordingly. Several sites were
begun simultaneously to undertake tunnel construction works using
trench less technology. Works were being carried out between the hours
of 07.00hrs and 19.00hrs but not on Sundays or public holidays.
However, in order to improve the progress of the works and therefore
reduce the overall programme and duration of disturbance it was
proposed that works could be extended from 19.00hrs to 23.00hrs or
perhaps even overnight.
The objective of the noise measurements was to provide sound
power levels (SWL) for several PME used routinely in the suite of
trench-less technology plant and to advise on how to reduce the SWL
from the individual PME by adding acoustic insulation where practicable.
This provided business value for the contractor and
was necessary since the suite of PME used in trench-less works contains
several pieces of equipment (de-sander etc.) not included on the list
of typical sound power levels for PME published by the noise authority.
Based on observation, some of the other typical construction PME used
by the contractors was quite new and well maintained and had SWL much
lower than the published sound power levels used for calculations under
local statutory procedures.
The measurement site was selected to provide an uncomplicated
environment to meet the normative qualifications for the acoustic
environment set in Annex A to the BS EN ISO 3746:1966. No major items
of plant or engines were near the PME being measured. The site was
adjacent to a busy main road but there was not heavy traffic flowing
during any of the measurement periods.


Noise measurement positions
The SWL for all major items of PME in the trench-less technology
suite and some other typical plant were measured. Noise measurement
followed the British and European Standard BS EN ISO 3746:1966
(Acoustics - Determination of Sound Power Levels of Noise Sources using
sound pressure – Survey method using and enveloping surface over a
reflecting plane).
Background monitoring of noise was undertaken with the PME switched
off immediately prior to noise measurements, intermittently during
noise measurements and immediately after noise measurements. Background
levels were in all cases >10dB (A) lower than the measured noise at
the microphone positions therefore no background correction was
applied. The weather conditions and noise sources were recorded before
and during monitoring. An anemometer was used to check wind speed
during the noise measurements. The measurement site is fairly well
sheltered and wind conditions on all occasions were still.
Sound Level Meter: O1dB SIP95 (MVI technologies group) Serial No. 988124
Acoustic Calibrator: O1dB type Cal 1 IEC 942:1988 Serial No.108800
The
monitoring professional calibrated the equipment prior to use. The
measurement surfaces and microphone positions from the reference box
were on the parallelepiped surfaces in strict compliance line with BS
EN ISO 3746:1996.
Business value could be derived since some of the
PME were unusual items of equipment for which the local noise
enforcement authority had no standard SWL. Others were items of
equipment which ran with SWL much lower than the standard SWL generally
accepted by the local noise authority. The measurements could therefore
be used for applications for construction noise permits and to
determine if suites of equipment could be operated at certain times
(e.g. 19.00hrs to 23.00hrs or later) in compliance with regulatory
requirements. Business value for the contractor and benefits to the
project accrued through greater flexibility in operating times, more
optimal use of resources and the advancement of the contract programme.
Further advice was provided on how to modify the plant and include
additional acoustic insulation, especially around the noisier elements
of the plant, in order to reduce further the noise impact and provide
additional business value.
could be derived since some of the PME
were unusual items of equipment for which the local noise enforcement
authority had no standard SWL. Others were items of equipment which ran
with SWL much lower than the standard SWL generally accepted by the
local noise authority. The measurements could therefore be used for
applications for construction noise permits and to determine if suites
of equipment could be operated at certain times (e.g. 19.00hrs to
23.00hrs or later) in compliance with regulatory requirements. Business value for the contractor and benefits to the project accrued through greater
flexibility in operating times, more optimal use of resources and the
advancement of the contract programme.
Further advice was provided on how to modify the plant and include
additional acoustic insulation, especially around the noisier elements
of the plant, in order to reduce further the noise impact and provide
additional business value.


Locations for additional acoustic insulation
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