A portable radio is sitting at the edge of a balcony 8.39m above the ground. The unit is emitting sound uniformly in all direction accident, it falls from rest off the balcony and continues to play on the way down. A gardener is working in a flower bed directly the falling unit. From the instant the unit begins to fall, how much time is required for the sound intensity level heard by the garc to increase by 10.0dB?

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