All types of trenching machines regardless of engine size may be tested under this Standard. It is not intended to cover operation of safety devices such as backup alarms or accessories such as paving breakers. The sound levels obtained by using the test procedures set forth in this SAE Standard are repeatable and are representative of the higher range of sound levels generated by machines under actual field operating conditions, but do not necessarily represent the average sound level over a field use cycle. For measurement and calculation of the operator's sound exposure, the procedure should follow SAE J1166.