Vibration and noise: the figures in the data sheet

Vibration is not measured in the same place

The clearest example is in our own catalogue. Swepac's pokers come as floor pokers with a pistol grip and as wall pokers with a long hose, and the vibration figures look dramatically different:

• PVE-D floor poker — 0.41 / 0.56 / 0.48 m/s² for 38, 50 and 58 mm, measured on the handle
• PVE wall poker — 1.4 / 1.8 / 2.3 / 2.7 / 2.48 m/s² for 38, 50, 58, 65 and 75 mm, measured on the hose two metres from the poker head

The measuring point is half the explanation

The floor poker is measured where the hand actually holds it, i.e. on the handle. The wall poker is measured on the hose two metres from the poker head — a point the operator does not necessarily hold at all.

The figures therefore do not describe the same thing, and a floor poker is not automatically four times kinder to the hands than a wall poker. Always read what is in brackets after the figure.

Other vibration figures in the catalogue

• Swepac TR 950E power trowel — 1.3 m/s²
• Swepac SV23E floor vibrator — 2.0 m/s²
• FBP-HP power screed — 4.03 m/s²
• Swepac SVM 25 — 4.5 m/s²

A(8): the figure depends on how long

Rotabroach gives both for the Magdrill Commando: 2 892 m/s² measured on the handle, and 0.13 m/s² as A(8), estimated from an assumed use of the machine.

A(8) is the value converted to a full eight-hour shift. The difference between the two figures is not the machine, but how long it actually runs. A machine with a high measured value that is used in short sessions can give a lower daily exposure than a gentler machine that runs all day.

Noise also has two figures

LWA is the sound power level — how much sound the machine emits in all directions. LpA is the sound pressure level at the operator's ear. The first concerns the surroundings, the second the person standing behind the machine.

• Husqvarna PG 450 — 93 dB(A) LWA, 79.2 dB(A) at the ear
• Husqvarna PG 400 — 98 dB(A) LWA, 84.7 dB(A) at the ear
• Husqvarna PG 680 and PG 820 — 101 dB(A) LWA, 82 dB(A) at the ear
• Swepac TR2000 HRM — 104 dB(A) LWA, 88 dB(A) at the ear
• FBP-HP power screed — 105.8 dB LwA, 90.8 dB LpA
• Swepac SVM 25 — 106 dB(A) LWA, 95 dB(A) at the ear

The two figures do not rank the same way

Note the PG 400 and PG 680. The PG 680 has the higher sound power of the two — 101 vs 98 — but the lower level at the ear: 82 vs 84.7. So the figures suggest that it emits more sound overall, but gives a lower sound pressure at the operator's ear. The differences are, however, on a par with the measurement uncertainty Husqvarna states for the PG 400: 2.5 dB(A) for sound power and 4 dB(A) for sound pressure at the ear.

If the machine is to be used indoors with people around, LWA is the figure that matters. If one person is to stand behind it all day, LpA is what counts.

When choosing

Tell us how many hours a day the machine will be used and by how many people. That is the information that turns the figures in the data sheet into something meaningful in practice.