ISO 20270:2019

Overview

ISO 20270:2019 - Acoustics: Indirect measurement of blocked forces defines an in situ, indirect method to characterize sources of structure-borne sound and vibration by estimating their blocked forces at the mechanical contact points to a receiver structure. The method uses measured frequency response functions (FRFs) of the assembled source–receiver system together with operational vibration measurements to solve an inverse problem and obtain blocked forces in the frequency domain. The procedure includes guidance to minimise uncertainties and an on-board validation procedure to evaluate result quality.

Key technical topics and requirements

• Scope and applicability
  • Applies only where vibration can be measured at all contact degrees of freedom (DOFs) between source and receiver.
  • Requires FRFs to be linear and time invariant.
  • Validated for stationary signals (frequency-domain presentation), but usable for time-varying signals with appropriate processing.
• Two-stage measurement approach
  • Passive FRF test of the assembled source–receiver structure (direct or reciprocal measurement).
  • Operational (running) test to capture vibration during normal operation.
• Inverse solution for blocked forces
  • Blocked forces are derived by combining FRFs and operational measurements; inverse problems can be sensitive to data inconsistency.
• Uncertainty control and validation
  • On-board validation procedure to estimate uncertainties and assess measurement quality.
  • Guidelines for minimising uncertainty and preliminary validation (artificial excitation).
• Test arrangement and instrumentation
  • Source may be installed in a real assembly or on a representative test stand.
  • Requirements for multi-channel analysers, vibration sensors, excitation means, and selection of indicator and validation DOFs.
• Reporting and annexes
  • Test report requirements and informative annexes (example test report, validation tests, case studies, DOF selection criteria, prediction guidance).

Practical applications and users

ISO 20270:2019 is intended for engineers and organisations involved in:

• NVH (Noise, Vibration, Harshness) and acoustic testing teams
• Mechanical, automotive, marine and building services engineers specifying or diagnosing vibrating components (e.g., pumps, motors, drives)
• Test laboratories performing source characterisation and transfer path analysis (TPA/SPC)
• Designers needing source data for predictive modelling of vibration and structure-borne sound

Common uses:

• Obtain blocked force data for technical specifications
• Input data for prediction of vibration/sound radiation in new assemblies
• In situ transfer path analysis and diagnostics to identify dominant force contributions

Related standards

• ISO 9611 - measurement of free velocity (related source-characterisation quantity)
• EN 15657 - reception plate method (alternative simplified approach)
• ISO 7626-1 - referenced for mechanical mobility and basic terms

Keywords: ISO 20270:2019, blocked forces measurement, indirect measurement, structure-borne sound, FRF, in situ blocked force method, transfer path analysis, NVH testing.