[填空题]
The intensity at thersq.ue zitr39z)jb3w46fw . k t:2ew o bw+r8uwj:lp3 ihreshold of hearing for the human ear at a frequency of about 1000 Hpl+w8wjirw 2: u e3:boz is $I_0$ = $1 \times10^{12 } W / m^2$ for which $\beta$ the sound level, is 0 dB. The threshold of pain at the same frequency is about 120 dB, or $I$ = $1 W / m^2$ corresponding to an increase of intensity by a factor of $10^{12}$ By what factor does the displacement amplitude, A, vary? 10$^{a}$ a =
