Various human body vibration measurements and assessments are defined in the ISO2631, ISO5349, ISO6954 standards and also in the EEC vibration directive 2002/44/EC. These assessments are based on the analysis of acceleration data that has been weighted (filtered) with appropriate vibration weighting values. The data must be in units of m/sec².

The vibration weighting values are defined in ISO8041:2005. Basically they are a set of filters that must be applied to the acceleration data in order to make evaluations and assessments on the effects of vibration on humans. They are defined as a set of weighting classes. Each class is associated with particular measurement directions, measurement positions and assessment type.

A selection of defined weighting classes are shown in Table 1. The directions are orientated such that the x direction is positive back to chest, the y direction is positive right side to left side and the z direction is positive from feet to head.

Table 1

The vibration weighting is applied by initially pre-filtering the data with a band pass filter between a lower frequency, f₁ and an upper frequency, f₂ as defined in Table 2. The appropriate weighting functions are then applied to the resulting band filtered data.

Table 2

Strict ISO8041 Compliance

ISO8041:2005 specifies that the acceleration data must be sampled at an adequate rate for the appropriate vibration weight class filter to be applied. In order to achieve strict ISO8041:2005 compliance the minimum adequate sample rate must be at least nine times the relevant low pass pre-filter cut off frequency, f₂. As shown in Table 2 the minimum ISO8041 compliant sample rate is 900 samples/second (9*f₂ = 9*100) for all vibration weight classes with the exception of class W_f where it is 6 samples/second (9*0.63) and class W_h where it is 11331 samples/second (9*1259).

The DATS software provides a particular function to perform the vibration weighting for a specified vibration weight class. In addition, DATS also provides a package to generate vibration assessment reports compliant with ISO2631-1, ISO2631-2, ISO2631-4, ISO5349 and ISO6954.

An example seat surface acceleration is shown below in Figures 1 and 2. Figure 1 shows the raw acceleration data and Figure 2 shows the acceleration after the appropriate ISO8041 compliant vibration weighting has been applied. In this example the data is seat surface data in the X direction so the appropriate vibration weight class is the W_d filter.

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Dr Mike Donegan

Senior Software Engineer at Prosig

Mike graduated from the University of Southampton in 1979 and then went on to complete a PhD in Seismic Refraction Studies in 1982. Mike then joined Prosig as a special applications engineer. He spent forty years at Prosig, researching & developing new algorithms and assisting customers with data analysis issues, until his retirement in 2024.

Latest posts by Dr Mike Donegan (see all)

• How Do I Measure Whole Body Vibration? - March 20, 2015
• Sampling and Filtering Data for ISO8041 Compliance and Human Body Vibration Data Weighting - July 10, 2014
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