SCHEDULE 3
PART 2METHOD OF DETERMINING AIRBORNE NOISE EMITTED BY LAWNMOWERS (ALSO REFERRED TO AS MOWERS IN THIS SCHEDULE) WITH A CUTTING WIDTH OF MORE THAN 120 CM AT THE OPERATOR POSITION
1. AIM
The aim of this method is to determine the noise emitted at the operator’s position(s) by all categories of lawnmowers with a cutting width exceeding 120 cm and having a seat attached in a suitable way to a structural component of the lawnmower.
It is not applicable for measurements to determine directly the level of an operator’s exposure at his post.
The values obtained by this method represent the data that make it possible to determine the equivalent continuous sound pressure level emitted by lawnmowers to the operator’s position(s). Save as otherwise indicated, these values include all tolerances.
2 SCOPE
2.1 Type of noise
This method is applicable to all types of noise emitted by lawnmowers at the operator’s position(s).
2.2 Type of lawnmowers
This method is applicable to all lawnmowers with one or more operator’s positions.
3 DEFINITIONS
3.1 Sound pressure level LpA
See Section 3.1 in Part 1.
3.2 Equivalent continuous sound pressure level LAeq:(t1, t2)
The equivalent continuous sound pressure level LAeq:(t1, t2) is obtained by applying the A-weighting as defined in IEC publication 651, first edition, 1979 to the equivalent continuous sound pressure level Leq:(t1, t2) defined below. This weighting is obtained inter alia by using the A-weighting filter in the measuring system.
The equivalent continuous sound pressure level for a limited period between intervals t1 and t2, Leq:(t1, t2), expressed in decibels, of a noise at a given point is defined by:
where:
p(t) is the instantaneous value of the sound pressure at this point, expressed in Pa;
p0 is the reference sound pressure, equivalent to 20 μPa;
Lp(t) is the sound pressure level at a given time at that point, expressed in dB;
t1 and t2 are the points indicating respectively the beginning and end of the reference period determining the Leq
t1 − t2 is the measurement interval.
4 CRITERION TO BE USED TO EXPRESS RESULTS
The acoustic criterion for the operator’s position(s) of lawnmowers is expressed by the equivalent continuous A-weighted sound pressure level LAeq(t1, t2).
5 MEASURING INSTRUMENTS
The specifications laid down in Section 5 of Annex I are to be used, with the extra requirement added to point 5.3 that the external diameter of the microphone must not exceed 13 mm.
6 PRESENCE OF THE OPERATOR
An operator shall occupy the operator’s position.
6.1 Clothing specifications
When he is present during the measurements, the operator must wear normal working clothes and all the equipment (e.g. safety helmet) normally prescribed for the post in question.
6.2 Height specifications of the operator(s)
6.2.1 Seated operator
The height of the operator(s) when seated (h) must be 0.93 ± 0.05 m, as shown in Figure 1.
7 MICROPHONE LOCATIONS
7.1 General
The microphone shall be located as specified in Section 7.2.
7.2 Microphone locations with operator present
The microphone is placed at 200 ± 20 mm from the median plane of the head and in line with the eyes and to the side of the head where the LAeq:(t1, t2) is highest.
Note:
To facilitate the placing of the microphone, it can conveniently be mounted on a frame or the helmet or a shoulder harness worn by the operator. For measurements when the operator is seated, the seat must be adjusted to allow the operator to reach the machine controls comfortably.
8 ENVIRONMENTAL CONDITIONS
8.1 Measuring site
The machine must, as far as possible, be installed in conditions identical to those specified in Sections 6.3 of Part 1.
8.2 Background noise
Background noise at each measuring point must be at least 10 dB(A) lower than the noise emitted by the machine.
9 INSTALLATION AND OPERATING CONDITIONS
9.1 General
The conditions required for installing and operating the lawnmower are laid down in point 6.2 of Part 1.
10 MEASUREMENTS AND CALCULATION OF RESULTS
10.1 Measurement interval T(= t2 − t1)
The measurement interval T must in principle be at least 15 seconds; in the case of a work cycle, it must be equal to the duration of a whole number of work cycles.
10.2 Determination of the equivalent continuous A-weighted sound pressure level (LAeq:(t1, t2)
This level is obtained either directly by integrating p (t) or by sampling of the pressure level LpA.
10.2.1 By integrating p2(t)
LAeq:(t1, t2) may be directly obtained by integrating the square of the A-weighted sound pressure during a period equal to t2 − t1 in accordance with the formula given in Section 3.2.
Digital or analogue integration may be used, e.g., with an integrating sound level meter.
10.2.2 Using the A-weighted sound pressure levels LpA
If a sound level meter is used, T is five seconds.
The number of measurements is 5.
10.3 Measurement of disturbances
The requirements are laid down in Section 7.1.3 of Part I.
10.4 Corrections to be made to measurements
10.4.1. Disturbances (temperature, humidity, altitude, etc)
The requirements are laid down in Section 8.6.3 of Part I.
10.4.2 Background noise
No correction is to be made for background noise.
11 DATA TO BE RECORDED
The report must contain the necessary data relating to the measurement of noise at operator’s position in accordance with Section 10 of Part 1.
Additional information must be given on the layout of the operator’s position during the measurements.
The report must also confirm that the equivalent continuous A-weighted sound pressure levels LAeq:(t1, t2) were obtained strictly according to this method of measurement.
Note:
If the measurements of sound pressure level at the operator’s position are carried out when the sound power level of the machine is determined, the data must be recorded in a single report.