Measuring condition, equipment and procedure of noise level under IMO Noise code
Measuring condition:-
On completion of the construction of ship, or as soon as practicable thereafter, measurement of noise levels in all spaces as specified in IMO code on noise level on board ship shall take place under the following condition---
1) Operating condition- The measurement should be taken both during sea trial and as well as during port stay
a) Sea trial:- Ship should be loaded or ballast on a straight course with engine running not less than 80% MCR. All machinery, navigational equipment should be in use at normal sea going condition. The measurement at places where emergency machinery are situated should be taken when the equipment are running.All mechanical ventilation, A/C should be in running condition. Doors and windows in general should be closed.
b) Port stay:- Measurement should be taken with cargo gear in operation. Machinery spaces noise measurement should be taken with all machinery operating in port condition.
2) Environmental condition:-
a) The depth of water should be more than 5 times the draught. There should not be large reflecting surfaces in the ship vicinity.
b) Meteorological conditions such as wind and rain, as well as sea state, should be such that they should not influence the measurement. Wind force 4 and 1 meter wave height should not be exceeded.
c) Care shall be taken that noise from external sound sources does not influence the noise level on board the ship.
Measuring equipment:-
Sound level meters should be manufactured to conform to IEC 61672 -1(2005) TYPE / CLASS 1 or to an equivalent standard acceptable to the administration.
Here Type 1 means that it satisfies the following specifications:-
It gives electroacoustical performance specifications for three kinds of sound measuring instruments--
a) A conventional sound level meter that measures exponential time weighted sound level
b) An integrating average sound level meter that measures time average sound level, and
c) An integral sound level meter that measures sound exposure level.
A single instrument can measure any or all three kinds of measurement.
CLASS 1 means it has wider frequency range and a tighter tolerance than class 2 instrument.
Measurement procedure:-
During measurement only seafarers necessary for the operation of the ship and persons taking the measurement shall be present in the space concerned.
Sound pressure level readings shall be taken in decibels using an A-weighting (dB(A)) and C-weighting (dB(C)) filter and if necessary also in octane bands between 31.5 and 8000 Hz.
The noise level measurement shall be taken with the integral sound level meter using spatial averaging and over a period of time until stable readings are found or at least 15 seconds in order to represent the average value from variations due to irregular operation or variation in the sound field. Reading should be made to the nearest decibel.
On completion of the construction of ship, or as soon as practicable thereafter, measurement of noise levels in all spaces as specified in IMO code on noise level on board ship shall take place under the following condition---
1) Operating condition- The measurement should be taken both during sea trial and as well as during port stay
a) Sea trial:- Ship should be loaded or ballast on a straight course with engine running not less than 80% MCR. All machinery, navigational equipment should be in use at normal sea going condition. The measurement at places where emergency machinery are situated should be taken when the equipment are running.All mechanical ventilation, A/C should be in running condition. Doors and windows in general should be closed.
b) Port stay:- Measurement should be taken with cargo gear in operation. Machinery spaces noise measurement should be taken with all machinery operating in port condition.
2) Environmental condition:-
a) The depth of water should be more than 5 times the draught. There should not be large reflecting surfaces in the ship vicinity.
b) Meteorological conditions such as wind and rain, as well as sea state, should be such that they should not influence the measurement. Wind force 4 and 1 meter wave height should not be exceeded.
c) Care shall be taken that noise from external sound sources does not influence the noise level on board the ship.
Measuring equipment:-
Sound level meters should be manufactured to conform to IEC 61672 -1(2005) TYPE / CLASS 1 or to an equivalent standard acceptable to the administration.
Here Type 1 means that it satisfies the following specifications:-
It gives electroacoustical performance specifications for three kinds of sound measuring instruments--
a) A conventional sound level meter that measures exponential time weighted sound level
b) An integrating average sound level meter that measures time average sound level, and
c) An integral sound level meter that measures sound exposure level.
A single instrument can measure any or all three kinds of measurement.
CLASS 1 means it has wider frequency range and a tighter tolerance than class 2 instrument.
Measurement procedure:-
During measurement only seafarers necessary for the operation of the ship and persons taking the measurement shall be present in the space concerned.
Sound pressure level readings shall be taken in decibels using an A-weighting (dB(A)) and C-weighting (dB(C)) filter and if necessary also in octane bands between 31.5 and 8000 Hz.
The noise level measurement shall be taken with the integral sound level meter using spatial averaging and over a period of time until stable readings are found or at least 15 seconds in order to represent the average value from variations due to irregular operation or variation in the sound field. Reading should be made to the nearest decibel.
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