vb7.4) Two sound sources vibrate in phase and have a sound power of 1.2 mW and 1.8 mW.
 Calculate the sound intensity at a point 5 m from the first and 7 m from the second source
 if the air temperature is -10 ° C and the frequency is 400 Hz after 0.010 s, 0.018 s and 0.25 s, 
respectively, after the sources went into operation? 
Which one is it noise level at this place?