AS ISO 9533:2020 Earth-moving machinery — Machine- mounted audible travel alarms and forward horns — Test methods and performance criteria
7.2  Setup for exterior alarm measurements
All sound measurements should be taken with the sound level meter set to “Fast response time weighting”, as defined in IEC 61672-1.
Sound measurements shall be taken for a minimum duration of 1 min at each test measurement location. When testing forward horns, such as electro-mechanical horns, sound measurements should not exceed a 1 min activation time without a pause between activations. The length of this pause should be specified by the horn manufacturer. Sound measurements performed on forward horns can be taken in minimum increments of 30 s.
The centre point of the measurement location should be 1,2 m ± 0,05 m from the ground with the normal to the rotational plane at 0° to 45° up from horizontal and facing the centre line of the MRB. The microphone should be held perpendicular to this plane and a minimum distance of 2 m shall be maintained by the test technician performing the measurement. See Figure 2.
An approximate rotational rate of 2 r/min should be used to traverse the microphone along the 260 mm radius circle during the measurements.
An apparatus can be used to measure the sound along the perimeter of a 260 mm ± 25 mm radius circle as shown in Figure 2. A description of how to build such an apparatus is given in Annex B.
7.3.1.1  General
At test measurement locations 1 to 7, measure and record the maximum overall sound pressure level using either method 1 or 2, as specified below.
7.3.1.2  Method 1 — Fixed sound level alarms
— Alarm Off
Capture the maximum sound pressure level with the reversing alarm off and the engine at maximum governor engine speed (high idle).
— Alarm On
Capture the maximum sound pressure level with the reversing alarm on and the engine at low idle or with the engine switched off.