[填空题]
(a) Estimate the power n2maw8 b mepr;q,3 rsef6 5qq-output of sound from e4w7ya f:qxbl)v4;pc66(c7gfsct zf a person speaking in normal conversation. Use Table 12–2. Assume the sound spr6gw(4cf v6e; abc7c):x 7p4lzyf sfqteads roughly uniformly over a sphere centered on the mouth. $\approx$ $ \times10^{ -6}$W(Round to the nearest integer)
(b) How many people would it take to produce a total sound output of 100 W of ordinary conversation? [Hint: Add intensities, not dB’s.]$\approx$ $ \times10^{7}$people
