All types of trenching equipment regardless of engine size may be tested under this recommended practice. 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 Recommended Practice are repeatable and are representative of the higher range of sound levels generated by the machinery 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 the SAE Recommended Practice J1166a.