Table 9.
The average value comparison of the physical acoustic property change: before and after Nakdong-iron and torch treatment

Subjects	Nakdong-iron treatment		Nakdong-torch treatment
	Before	After	Before	After
Mass (g)	15.26	14.76	18.74	18.14
Length (mm)	298.68	303.03	303.03	301.50
Thickness (mm)	9.72	9.59	10.14	10.03
Density (kg/m2)	265.53 (8.25)	256.52 (6.93)	290.22 (10.50)	285.88 (10.43)
Dynamic Young's Modulus (GPa)	5.29 (0.28)	5.49 (0.65)	5.49 (0.48)	5.35 (0.48)
Sound Velocity (m/s)	4462 (116)	4620 (283)	4347 (196)	3268 (159)
Sound Radiation Coefficient (m4/kg s)	16.83 (0.78)	18.03 (1.34)	15.01 (1.00)	15.14 (0.91)