ISO 20270 is a safety standard on indirect measurement of blocked forces determining structure-borne sound and vibration in acoustics.
ISO 20270 specifies a method where a vibrating component (a source of structure-borne sound or vibration) is attached to a passive structure (or receiver) and is the cause of vibration in, or structure-borne sound radiation from, the assembly. Examples are pumps installed in ships, servo motors in vehicles or machines, and plants in buildings. Almost any vibrating component can be considered as a source in this context.
ISO 20270 provides a method for measurement and presentation of blocked forces, together with guidelines for minimizing uncertainty. ISO 20270 provides a method for measurement and presentation of blocked forces, together with guidelines for minimizing uncertainty. ISO 20270 is about a method that evaluates the quality of the results through an on-board validation procedure but does not comment on the acceptability or otherwise of the results.
Note 1: Due to the need to measure vibration at all contact degrees of freedom (DOFs) (connections between the source and receiver ISO 20270 can only be applied to assemblies for which such measurement is possible.
Note 2: ISO 20270 is applicable only to assemblies whose frequency response functions (FRFs) are linear and time-invariant. The source can be installed into a real assembly or attached to a specially designed test stand.
Note 3: ISO 20270 has been validated for stationary signals such that the results can be presented in the frequency domain. However, the method is not restricted to stationary signals: with appropriate data processing, ISO 20270 is also applicable to time-varying signals such as transients and shocks (provided linearity and time invariance of the FRFs are preserved).
Note 4: prediction of sound and vibration in a new assembly [as in b) above] does not form a normative part of ISO 20270, although guidelines for prediction are provided in Annex E.
ISO 20270 on indirect measurement of blocked forces is relevant to:
ISO 20270 has been developed in response to demand from mechanical industries for an agreed method of specifying the "source strength" of sources of structure-borne sound and vibration. Quantities that independently characterize a source are the free velocity and blocked force: specifies a measurement procedure for the former in which the machine, a vibration source, is mounted on soft mounts to approximate free suspension.
ISO 20270 describes an indirect method for the measurement of blocked forces using an inverse method. The indirect measurement, as defined in ISO 20270, can theoretically be carried out with the source attached to any receiver structure. Essentially the same measurement techniques are used in the diagnosis of structure-borne sound using "transfer path analysis" (TPA), also called "source path contribution" analysis (SPC). A method of characterizing sources of structure-borne sound and vibration by the indirect measurement of blocked forces at the points of connection to supporting, or receiver, structures are described in ISO 20270. The measurement method is applied in situ, which means that the source is connected to a receiver structure while the measurements are performed. ISO 20270 aims to provide an alternative for structure-borne sound sources not compatible with the reception plate approach or where more detail is needed about the distribution of the forces.
The blocked forces obtained from ISO 20270 can be used for the following purposes:
Overall, ISO 20270 is useful as it assists the user with a method that specifies a two-stage measurement procedure comprising, first, a passive test in which frequency response functions (FRF) of the assembled source-receiver structure are measured, and secondly, measurement of vibration in an operational test.
ISO 20270