. What are the conditions for an echo to be heard?
The conditions that have to be satisfied to hear an echo are as follows:
•The distance between the source of sound and the reflector should be at least 17.2 m.
•The size of the obstacle/reflector must be large compared to the wavelength of the incident sound.
•The intensity or loudness of sound should be sufficient for the reflected sound reaching the ear to be audible.
•The original sound should be of short duration.
•The time interval between the original sound and the reflected sound should be at least 0.1 s.