The external ear is divided into auricle and external auditory canal. Auricle has the function of judging the direction of sound source, collecting and amplifying sound waves. The sound coming from the front directly enters the ear, and the sound coming from the back is blocked by the auricle, so it plays a certain role in sound localization. Collecting and amplifying sound waves is related to the funnel-shaped auricle. For example, in order to hear more clearly, the elderly with poor hearing often curl their palms and put them above the auricle to increase the length of the auricle and enhance its sound collection function. Experiments show that the auricle can enhance the sound by about 10dB (decibel) for the sound in the frequency band of 4000-5000Hz, and the enhancement degree is related to the depth and cross-sectional area of the auricle. The auricle edge also has a gain of several decibels to the sound pressure.

The external auditory canal is a sound wave conduction channel. According to the principle of physics, a pipe with one end closed can amplify sound waves to four times the length of the pipe. Because the end of the external auditory canal is an elastic tympanic membrane, and the external auditory canal is an S-shaped bend, coupled with the amplification of the external auditory canal, the external auditory canal has a more obvious improvement on the middle and high frequency parts of the incoming sound source, which will help the human ear distinguish and understand sound and speech information.