BS EN ISO 2922:2020 pdf download.Acoustics — Measurement of airborne sound emitted by vessels on inland waterways and harbours.
4 Measurement quantities
4.1 Frequency weighting A shall be used for all measurements. The time weighting shall be set to slow (S) for all measurements.
4.2 Care should be taken to avoid any influence on the result from unwanted sound signals, for example noise from the wind on the microphone of the measuring equipment, electrical interferences, or noise from extraneous sound sources not under consideration.
4.3 The quantities that shall be determined at all microphone positions in acceptance and monitoring tests are the A-weighted sound exposure level, L E,A,T , received from the operation of the vessel, and the maximum AS-weighted sound pressure level, L pASmax .
4.4 If, in addition to the sound exposure level, spectral analysis in acceptance tests or determination of some special acoustical characteristics of vessels is needed, the quantities that shall be measured are the unweighted or C-frequency weighted, octave-band or one-third-octave-band S-time weighted sound pressure levels, in decibels, at the time of maximum sound pressure, or the unweighted or C-frequency weighted, octave-band or one-third-octave-band sound exposure levels, in decibels (dB).
4.5 When measurements are made at some distance from the source, the levels observed can be considerably affected by the weather conditions. For example, the attenuation of sound due to air absorption is affected by the temperature and humidity of the air. In addition, the refraction of sound waves due to wind and temperature gradients affect the levels received at a particular position. It is recommended that measurements taken in extreme or atypical conditions be avoided. If possible, a value obtained under typical climatic conditions, and an indication of the range of values obtained under other climatic conditions, should be included in the test report.
5 Measuring equipment
5.1 Equipment specifications The instruments for measuring sound pressure levels, including microphone(s) as well as cable(s), recording devices and other accessories, if used, shall meet the requirements for a class 1 instrument according to IEC 61672-1 for free field or random incidence application, as appropriate. Filters shall meet the requirements for a class 1 instrument according to IEC 61260-1. A wind speed anemometer with a maximum permissible error of ±10 % shall be used. An engine speed tachometer with a maximum permissible error of ±50 r/min shall be used.
5.2 Windscreen A suitable windscreen shall be used to reduce the influence of the wind on the reading. When it can be expected that the wind-induced signal will be within 10 dB of the average sound level induced by the vessel under investigation, windscreens shall be used which, together with the sound level meter, meet the requirements of a class 1 instrument according to IEC 61672-1.BS EN ISO 2922 pdf download.