Задача 40976.

The loudness of the sound frequency of 1 kHz decreased by 30 background when passing through a thin plywood wall. What was the intensity of the sound, if before the passage of the partition it was 10 ^ -8 W / m ^ 2?

Detailed solution with a brief record of the conditions, formulas and laws used in the decision, the conclusion of the calculation formula and the answer.
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