The human ear is a sense organ that allows humans to hear sounds around them. The ear converts pressure variation in the air with audible frequencies into electrical signals that travel to the brain with the help of auditory nerve. Note: The human ear is usually described as having three parts- the outer ear, the middle ear and, the inner ear. The pinna in outer ear collects the sound waves from the surroundings.

An echo is a sound that is repeated after getting reflected from various obstacles. Note: When sound waves hit a hard surface, it gets reflected back just like a ball bounces off a wall. This phenomenon is called an echo. To hear a distinct echo, then the echo (or reflected sound) must reach our ear 0 . 1 s after the original (or incident) sound.