(a) Walls of auditorium should be good absorbers to provide optimum value of reverberation time$T = \frac{0.16V}{\sum as}$where$V$ is volume of hall and $\sum$ as is total absorption of the hall.
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.