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DADiSP / ISO2631

ISO 2631 Frequency Weighting

ISO 2631 Frequency Weighting Module

The international ISO 2631 Standard outlines methods for the measurement, evaluation and assessment of human exposure to Whole - Body Vibration (WBV). An evaluation of the effect of exposure to vibration on humans is performed by weighting the root-mean of acceleration data transmitted via supporting structures.

Because the human response to vibration is a function of frequency, acceleration data is filtered with frequency weighting curves as specified by the standard to correlate the vibration measurements to a person's response to vibration.

ISO 2631 Standard

It is necessary to use standard methods for frequency weighting so that results from different measurements using different equipment can be compared. The ISO 2631 standard describes weighting filters for combinations of sitting, standing, and recumbant positions for the analysis of health, discomfort, perception and motion sickness.

Several frequency curves are presented covering the most significant combinations of vibration axes and effects (health, comfort, perception, motion sickness). Three of these curves are used in the evaluation of vibration from the point of view of health effects, and two in the procedure of assessment of vibration severity.

Standard Frequency Weighting Filters

The ISO 2631 Standard defines 8 frequency weighting curves. In addition, the ISO 5349 Standard defines a frequency weighting curve for hand vibration and the British BS 6841 Standard defines a curve for activity interference. The ISO 2631 Module supports all ten of these standard filter types as described below:

ISO 2631, ISO 5349, BS 6841 Frequency Weighting Filters

Wb Vertical Whole-Body Vibration, Z Axis, Standing, Seated or Recumbant Person ISO 2631-4
Wc Horizontal Whole-Body Vibration, X Axis, Seat Back, Seated Person ISO 2631-1
Wd Horizontal Whole-Body Vibration, X or Y Axis, Standing, Seated or Recumbant Person ISO 2631-1
We Rotational Whole-Body Vibration, All Directions, Seated Person ISO 2631-1
Wf Vertical Whole-Body Low Frequency Vibration, Z Axis, Motion Sickness, Seated or Standing Person ISO 2631-1
Wg Vertical Whole-Body Vibration, Z Axis, Activity Interference BS 6841
Wh Hand-Arm Vibration, All directions ISO 5349-1
Wj Vertical Head Vibration, X Axis, Recumbant Person ISO 2631-1
Wk Vertical Whole-Body Vibration, Z Axis, Seated, Standing or Recumbant Person ISO 2631-1
Wm Whole-Body Vibration in Buildings, All Directions ISO 2631-2

High Precision Filters

The desired filter coefficients are generated by converting the analog filter specifications detailed in the supported standards into the digital domain using the bilinear transform method. Because the filter is comprised of several cascaded sub-filters, the coefficients of each sub-filter are calculated and combined via convolution to produce the equivalent coefficients of the resulting monolithic digital filter.

The resulting coefficients are in second order CASCADE form and are used to process the data with high numeric precision and stability.

One Step Processing

The design and processing of data with a supported frequency weighting filter is accomplished in one easy step. Both an interactive dialog box interface and simple command line functions are provided. For example, to process acceleration data in Window 1 with an ISO 2631 Wk frequency weighting filter:

  filt2631(w1, "Wk")

To display the ISO 2631 Wk weighting curve in the frequency domain:


The dialog box interface makes selecting and processing data with a frequency weighting filter as simple as a mouse click.


DADiSP/ISO 2631 requires DADiSP 6.0 B17 or higher. Contact us for information about updating your current version of DADiSP.

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