UNI EN ISO 9612:2011 pdf free download – Acoustics . Determination of ocpational noise exposure – Engineering method.
MEASUREMENTS
Selection of instrumentation
Measurements shall be performed using the following types of instrumentation (see also 5.1):
a) personal sound exposure meter worn by the worker whose noise exposure is being determined;
b) integrating-averaging sound level meter placed in discrete positions, or held in the hand whilst following a mobile worker.
Personal sound exposure meters may be used for measurements in all types of work situations. It is the preferred method when making long duration measurements for a mobile worker engaged in complex or unpredictable tasks or carrying out a large number of discrete tasks.
For measurements of single or multiple tasks at fixed workstations, hand-held or fixed sound level meters may be used.
12.2 Field calibration
Field calibration includes an acoustic calibration check of the entire measuring system, including the microphone, and is a distinct survey procedure separate from laboratory calibration. A field calibration shall consist of applying a sound calibrator meeting the requirements of IEC 60942:2003, class 1, to each microphone and recording the measured level at one or more frequencies within the frequency range of interest. Field calibration shall be carried out in a quiet location.
Before each series of measurements and at the start of each daily series of measurements, a field calibration with appropriate adjustment shall be performed. At the end of each series of measurements and at the end of each daily series of measurements, a field calibration without adjustment shall be performed. If the reading at any frequency at the end of a series of measurements differs from the reading of that frequency at the beginning of the series by more than 0,5 dB, the results of the series of measurements shall be discarded.
12.3 Instrument worn by the worker
The microphone shall be mounted on the top of the shoulder at a distance of at least 0,1 m
from the entrance of the external ear canal at the side of the most exposed ear and should
be approximately 0,04 m above the shoulder. The microphone and the cable shall be
fastened in such a way that mechanical influence or covering by clothing do not lead to
false results.
Care shall be taken not to disturb the work performance and especially not to introduce
safety risks. Similarly, care shall be taken to avoid false contributions. See also 13.2.
Note When using measuring instruments worn by the worker or in other cases when the microphone is placed very close to a worker’s body, the measurement result is affected by screening effects and reflections by the body.
This is especially valid for high-frequency noise and small noise sources at a short distance from the ear. In such cases, the measurements should be performed with microphones placed at both sides of the head in order to establish the exposure of the most exposed ear.
Note 2 The advantage of using personal sound exposure meters is that the workers being monitored do not have to be followed closely and several workers can be tested simultaneously.
The worker being monitored shall be informed of the purpose of the measurement.
Workers shall be advised not to remove the measuring instrument during the entire measurement period and to perform their work normally.