Question

Echoes are not heard in a small room . Why?

An echon is heard is heard on a day when the temperature is 30 C will the echo be heard sooner or later ifthe temp falls to 4 C

Answer 1

Echo is the phenomenon of reflection of sound from a surface.
Any sound heard by human ears persists for about 0.1 s. So, to hear distinct echo the minimum distance between the source of sound and the reflector must be 17 m. This is why echo is not heard within a small room.
Speed of sound decreases with decreasing temperature. So, the sound will travel slower at a lower temperature and also echo will come back slower if the speed of sound is less.