Answer:
72.04 dB.
Step-by-step explanation:
The intensity level of 60dB corresponds to the sound intensity 
 given by the equation
 given by the equation 

where 

solving for 
 we get:
 we get: 



Now, when 16 violins are playing the intensity 
 becomes
 becomes 

which on the decibel scale gives

 .
.
Thus, playing 16 violins together gives the intensity level of 72 dB.