The source frequency of a harmonic spherical sound wave is 1000 Hz. Air density is 1.3 kg/m^3, its temperature is 290 K, mole mass is 29 g/mol. At a distance of 100 m from the source, the wave intensity level is 80 dB. Write the wave equation. At what distance from the source will the sound intensity level reach the pain threshold of 120 dB?

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