3. ANALYSIS
3.1. Frequency Analysis
Power spectral densities (PSD) were calculated for all acceleration
signals. The power spectra show the distribution
of energy across the frequency spectrum. Vibration evaluations
were performed according to the recommendations in the
BS 6841.4 This involved the application of frequency weightings,
multiplication of factors to allow for different sensitivity
of the body in different axes, calculation of root-mean-square
(rms) and VDV, and summation of values over different axes.
The acceleration was frequency-weighted using the frequency
weightings defined in the BS 6841 over the frequency range
0.5 to 80 Hz. The three frequency weightings and multiplying
factors for the different axes are listed in Table 2. The
frequency-weighting values are shown in Fig. 4.