When a sound is reflected from a distant object, an echo is produced. Let the distance between the reflecting surface and the source of sound production remain the same. Do you hear the echo sound on a hotter day?
The sensation of sound persists in the human brain for about 0.1s. To hear a distinct echo, the time interval between the original sound and the reflected one must be at least 0.1s. Therefore, the total distance covered by the sound from the point of generation to the reflecting surface and back should be at least (344 m/s)0.1 s=34.4 m Thus, for hearing distinct echoes, the minimum distance of the obstacle from the source of sound must be half of this distance, that is, 17.2 m. Speed of sound will increase with the increase in temperature. Therefore, on a hotter day the speed of sound will be greater hence echoes may be heard more than once because of multiple reflections of sound result will be no distinct echo will be heard by humans.
