A certain siren radiates sound uniformly in all directions. At a distance of 17 m from the siren, the intensity level is 49 db. How many watts of power does this siren put out? The threshold of human hearing is 1.0 × 10-12 W/m2.

The power is  

Explanation:

From the question we are told that

   The distance from the siren  is  

  The intensity level is  

   The threshold of hearing is  

Generally the intensity level is mathematically represented as

Where I is the intensity at which the siren radiates the sound

substituting values  

=>    

Now the amount of power the siren put out is mathematically evaluated as

Where A is the area  of the siren which is taken as a sphere  and it  is mathematically evaluated as

So  

substituting values

the answer is a. hope this .