ISO 3740:2019

ISO 3740:2019 pdf free.Acoustics——Determination of sound power levels of noise
sources——Guidelines for the use of basic standards.
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain term inological databases for use in standardization at the following addresses:
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3.1 emission <acoustics> airborne sound radiated by a well-defined noise source (e.g. the machine under test) under specified operating and mounting conditions
Note 1 to entry: Emission values may be incorporated into a product noise declaration, product label and/or product specification. The basic noise emission quantities are the sound power level of the source itself and the emission sound pressure levels at the work station and/or at other specified positions (if any) in the vicinity of the source.
ISOURCE: ISO 12001:1996, 3.3, modified — Note ito entry “product noise declaration” added.1
4 Sound power level
4.1 Basic information
The sound power level characterizes the mean airborne acoustic energy flow from the source into
the environment for a given mounting and operating condition and represents an intrinsic acoustic
characteristic of the source that is independent of the environment in which it is installed. It is often
denoted as an A-weighted sound power level, LwA, in dB.
4.2 Reasons for the determination of sound power levels
Example situations where the A-weighted sound power level of a machine, equipment and product can be of interest are:manufacturer noise emission declarations in the instructions and the sales literature according to regulations for machinery safety;customer need for input to sound exposure prediction models which can support legal requirements for carrying out a noise exposure risk assessment;customer need for comparison with the state of the art of noise emission, for comparing the data of competing machinery, equipment and products to support the“Buy Quiet” objective;checking the noise emission level of machinery, equipment and products in specifications regardless of the environment in which they operate.
4.3 Basic procedures for determining sound power levels
Sound pressure, sound intensity and vibratory velocity level measurements form the basis of different procedures to determine sound power level. These procedures include
evaluation of the spatial mean-squared sound pressure built up in highly reflective environments
(ISO 3741, ISO 3743-1, ISO 3743-2);
— comparison of the sound pressure levels in octave frequency bands of a noise source under test with those of a calibrated reference sound source (150 3747);
— evaluation of the flow of sound energy by a direct measurement of the sound intensity (ISO 9614-1, ISO 9614-2, ISO 9614-3) near the source or the free field approximation of the intensity through measurement of the squared sound pressure (ISO 3744, ISO 3745, ISO 3746) emitted by the source, both measurements carried out on an enveloping surface;
— evaluation of the partial flow of airborne sound energy emitted by vibrating solid structures of the machine, using measurements of the vibratory velocity over the surface of vibrating solid structures
(ISO/TS 7849-1, ISO/TS 7849-2).
Microphones used to measure the sound pressure level at specific positions around the source under test measure the sum of the direct sound from the source and the contributions from other sound sources in the measurement room plus the sound which is reflected by walls, floor, ceiling and obstacles. Therefore, corrections to cope with these influences are required in practice. These are the background noise correction, K1, and the environmental correction, K2. Please refer to Annex D for examples of practical applications of ISO 3744 and ISO 3746.ISO 3740 pdf download.

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