# Decibel problem

1. Mar 23, 2005

### Salty

A portable radio is sitting at the edge of a balcony 5.1m above the ground. The unit is emitting a sound uniformly in all directions. By accident, it falls from rest off the balcony and continues to play all the way down. A gardener is working in a flower bed directly below the falling unit. From the instant the unit begins to fall, how much time is required for the sound intensity level heard by the gardener to increase by 10 dB?

2. Mar 23, 2005

### MathStudent

hint: first find the distance from the radio the gardener would have to be to here an increase in intensity of 10dB

A useful equation is the inverse square law for intensity

$$\frac{I_1}{I_2} = (\frac{r_2}{r_1})^2$$

where I1 is the intensity at a distance r1, and I2 is the intensity at a distance r2.