Table 1.

Dose per hole and reduction in the time-weighted average sound level (TWA) by mine and test number. Data are based on 100 holes drilled per device.

Mine	Test #	Dose/hole without isolator (% of PEL)	Dose/hole with isolator (% of PEL)	Relative dose/hole reduction (%) with isolator	PEL TWA reduction (dB(A))
Mine A	Test 1	0.50	0.34	32	2.8
	Device 1
	Test 2	0.43	0.21	51	5.2
	Device 2
	Test 3	0.80	0.60	25	2.1
	Device 2
Mine B		1.83	1.25	32	2.8
Mine C		0.69	0.45	35	3.1
Mine D		0.90	0.66	27	2.2