1.1 General
This International Standard specifies a method for measuring the emission sound pressure
levels of machinery and equipment, at a work station and at other specified positions
nearby, in an essentially free field over a reflecting plane. A work station is occupied
by an operator. It may be located in open space in the room where the source operates,
or in a cab fixed to the source, or in an enclosure remote from the source. One or
more specified positions may be located in the vicinity of a work station, or in the
vicinity of an unattended machine. As some of these positions may be occupied occasionally
or regularly, they are sometimes referred to as bystander positions.
Emission sound pressure levels are measured as A weighted and, if required, C-weighted
peak, and in frequency bands.
NOTE 1 The contents of this and related International Standards are summarized in table 1 of
ISO 11201:1995.
This International Standard specifies requirements for the engineering grade of accuracy
on the test environment and instrumentation. Corrections are applied for background
noise, but not for the acoustic environment. Instructions are given for the installation
and operation of the machine under test and for the choice of microphone positions
for the work station and for other specified positions. The purpose of the measurements
is to permit comparison of the performance of different units of a given family of
machinery or equipment, under defined environmental conditions and standardized mounting
and operating conditions. The data obtained may also be used for the declaration and
verification of emission sound pressure levels as specified in ISO 4871.
NOTE 2 At any given position in relation to a particular machine, and for given mounting
and operating conditions, the emission sound pressure levels determined by the method
of this International Standard will in general be lower than the directly measured
sound pressure levels for the same machine in the typical workroom where it is used.
This is due to reverberation and the contributions of other machines. A method of
calculating the sound pressure levels in the vicinity of a machine operating alone
in a workroom is given in ISO 11690‑3. Commonly observed differences are 1 dB to 5 dB, but in extreme cases the difference
may be even greater.