The narrow duct from the pinna to the tympanic membrane is called the external auditory meatus. It is a curved tunnel. Its outer two-thirds is made up of cartilage and the inner one-third is made up of bone. Its length is 2.5 cm and width is 0.7 cm. It contains wax glands and fine hairs. Through this the sound waves reach the tympanic membrane. Due to wax and hair, dust and germs cannot enter inside.