A person speaking normally produces a sound intensity of $$40$$ dB at a distance of $$1$$ m. If the threshold intensity for reasonable audibility is $$20$$ dB, the maximum distance at which he can be heard clearly is

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Infinity Learn · Accepted Answer

$$dB=10$$ $$log10II0$$; where $$I0=10$$−$$12$$ Wm−$$2Since$$ $$40=10log10I1I0$$⇒$$I1I0=104$$       ....(i)Also$$  $$20=10log10I2I0$$⇒$$I2I0=102$$        ....$$(ii)⇒$$I2I1=10$$−$$2=r12r22$$⇒$$r22=100r12$$⇒$$r2=10$$ m                                                                  $${$$∵$$r1=1$$ $$m}$$

A person speaking normally produces a sound intensity of 40 dB at a distance of 1 m. If the threshold intensity for reasonable audibility is 20 dB, the maximum distance at which he can be heard clearly is

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