Question

why we cannot hear echo produced in classroom???????

Answer 1

because echo produced ina empty class room . And in the there is a tables and chairs . so it is difficult to produce an echo

Answer 2

Because d minimum distance between d source n d reflecting for an echo to occur is 17 metres. Because d original sound n d reflected sound r heard at d same tym. If ur classroom is as big as 17 metres an echo will definately be heard. ;)