1

Fig. 1. Study layout.

Table 1. Chipper characteristics and operators’ weight.
Chipper # 1 2 3 4
Manufacturer A A B B
Type Tractor Truck Tractor Truck
Power [kW] 286 397 217 353
Drum speed [rpm] 600 600 560 560
Mass tractor/ truck [kg] 10 830 26 000 10 450 26 820
Mass chipper [kg] 17 500 Included in truck’s
weight 		16 000 Included in truck’s
weight
Total setup mass [kg] 28 330 26 000 26 450 26 820
Year of construction 2012 2011 2008 2011
Operating hours [PSH15] 170 970 4741 3280
Seat suspension Mechanical Mechanical Mechanical Mechanical
Weight of operator [kg] 90 93 103 70
Table 2. Raw material characteristics per chipper model and wood species.
Species Poplar Spruce Poplar Poplar Oak Oak Oak Oak
Chipper model A1 A2 B3 B4 A1 A2 B3 B4
Fresh density [kg/m3] 644 650 680 621 950 866 869 817
Oven-dry density [kg/m3] 411 438 483 431 673 658 641 616
Water content [%] 36 33 29 31 29 24 26 25
Diameter (Mean ± Sd) [cm] 25 ± 11 15 ± 5 15 ± 7 25 ± 10 20 ± 8 25 ± 10 17 ± 6 23 ± 9
2

Fig. 2. Vibration during chipping per setup variant, manufacturer and wood type. The bottom and top of the box represent the first (25%, lower end) and third (75%, upper end) quartiles. The black strip in the middle is the median. The brackets outline maximum deviations in both directions.

Table 3. Frequency-weighted vibration acceleration (rms) in m/s² – Manufacturer A.
Working element Wood type Tractor Truck
Mean Sd Min Max Mean Sd Min Max
Chipping Soft 0.25 0.03 0.20 0.29 0.35 0.02 0.31 0.38
Hard 0.35 0.04 0.26 0.39 0.33 0.01 0.30 0.34
Driving Soft/Hard 0.64 0.05 0.58 0.68 0.60 0.09 0.50 0.77
Delays Soft/Hard 0.11 0.04 0.07 0.17 0.06 0.01 0.04 0.07
Table 4. Frequency-weighted vibration acceleration (rms) in m/s² – Manufacturer B.
Working element Wood type Tractor Truck
Mean Sd Min Max Mean Sd Min Max
Chipping Soft 0.27 0.02 0.23 0.31 0.63 0.02 0.58 0.65
Hard 0.31 0.03 0.27 0.35 0.70 0.04 0.65 0.78
Driving Soft/Hard 0.84 0.17 0.53 1.08 0.50 0.12 0.24 0.64
Delays Soft/Hard 0.05 0.02 0.02 0.08 0.13 0.02 0.10 0.14
3

Fig. 3. Noise level for various working elements separated for setup variant, for manufacturer A and B. The bottom and top of the box represent the first (25%, lower end) and third (75%, upper end) quartiles. The black strip in the middle is the median. The brackets outline maximum deviations in both directions.

Table 5. Noise level for various working elements during chipping hardwood – Manufacturer A.
Working element Machine type Lp,A,eq,Te [dB(A)] Lp,C,peak [dB(C)]
Mean Sd Min Max Mean Sd Min Max
Chipping Tractor 77.4 1.1 75.9 79.3 102.3 1.2 100.1 103.9
Truck 73.5 1.0 71.9 75.5 101.4 1.2 99.7 103.2
Driving Tractor 72.1 1.2 70.1 73.3 99.9 0.8 98.8 100.8
Truck 70.0 1.0 68.5 72.3 99.1 0.8 97.9 100.1
Delays Tractor 68.8 0.5 68.1 69.7 93.1 0.6 92.4 94.4
Truck 64.9 1.0 63.1 66.1 90.4 0.5 89.7 91.2
Table 6. Noise level for various working elements during chipping hardwood – Manufacturer B.
Working element Machine type Lp,A,eq,Te [dB(A)] Lp,C,peak [dB(C)]
Mean Sd Min Max Mean Sd Min Max
Chipping Tractor 73.6 0.9 71.9 74.9 100.6 1.4 98.1 102.4
Truck 79.4 1.2 77.9 81.1 100.7 1.1 99.7 102.3
Driving Tractor 71.2 1.3 69.7 73.6 100.2 0.9 98.7 101.7
Truck 68.3 1.2 65.9 70.1 99.6 0.9 97.9 100.7
Delays Tractor 67.6 0.7 66.7 68.8 90.6 0.8 89.1 92.1
Truck 63.9 1.0 62.8 65.3 90.5 0.6 89.7 91.7
Table 7. Total vibration and A(8) values during the chipping of hardwood.
Task Time [hours] Total vibration value aw [m/s²]
Chipper A1 Chipper A2 Chipper B3 Chipper B4
Chipping 4.8 0.35 0.33 0.27 0.70
Driving 0.4 0.64 0.60 0.84 0.50
Delays 2.0 0.11 0.06 0.05 0.13
Maintenance and breaks
(no exposure to vibration) 		0.8 0 0 0 0
A(8) 8.0 0.31 0.29 0.28 0.56
Table 8. Sound level per task and total exposure values during the chipping of hardwood.
Task Time [hours] Sound level Lp,A,eq,Te [dB(A)]
Chipper A1 Chipper A2 Chipper B3 Chipper B4
Chipping 4.8 77.4 73.5 73.6 79.4
Driving 0.4 72.1 70.0 71.2 68.3
Delays 2.0 68.8 64.9 67.6 63.9
Maintenance and breaks
(machine not operating) 		0.8 55.0 55.0 55.0 55.0
Total (LA,EX, 8h) 8.0 75.5 71.7 72.0 77.3