The ears have a complex anatomy and an equally intricate physiology. The students pursuing Hearing Instrument Specialist (HIS) and other similar programs are often confused by the complicated descriptions and explanations of anatomy and physiology of ears and related structures. The author has a longstanding experience of teaching undergraduate and postgraduate medical students. He has made an earnest attempt to present these challenging topics in a simple and easy to understand manner for HIS program students. The book has a number of illustrations that make grasping of anatomical details easy. Where ever needed the applied aspects have also been discussed.

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The external ear shields the tympanic membrane (TM) from mechanical trauma by providing a convoluted entrance leading to auditory apparatus. It also acts as an acoustic antenna. For descriptive purposes this acoustic antenna may be divided into three parts. The pinna along with head and torso functions as diffracting system. The concha and EAC act as acoustic resonators. The tympanic membrane acts as a point of acoustic termination. These three components do not work in isolation rather these work in tandem with each other. The net result is transformation of sound pressure from free field to TM and addition of significant gain at higher frequencies. (Dancer, 2016) (Shaw, 1974)

The net result of this distinct structure and design of the external ear is a selective boost to sound pressure to the tune of 30 to 100 times for frequencies around 3 kHz. It must be remembered that majority of human speech frequencies are spread around this bandwidth. The boost provided by the external ear makes the humans particularly sensitive to sound frequencies around 3 kHz. (Purves D, 2001)

The pinna, its concha bowl, and EAC provide amplification to sound waves. If a sound wave is incident on the head at an angle of 45⁰ the pinna contributes 3 dB amplification at 4 kHz. The concha contributes a maximum gain of 10 dB between 4-5 kHz. The EAC provides nearly 10 dB of gain which reaches its pinnacle at 2.5 kHz. The various constituents of external ear put together provide maximum amplification between frequencies of 2-5 kHz. The maximum gain (20 dB) occurs at 2.5 kHz. (Bruns, 2021)

The specific resonance qualities of ear canal are different in different people as it varies in cross-sectional diameter depending on age, gender, and genetic factors. (Diana C. Emanuel, 2022)

Normal binaural hearing is required to localize the source of sound. In case the source of sound is placed directly in front of a person’s head, in normal circumstances it is expected to reach both of his/her ears at the same time. On the other hand, if the source of sound is situated on either side (say left side) the sound reaches left ear earlier than the opposite (right) ear. The arrival of sound will not only be delayed at the right ear it will also be somewhat attenuated in intensity. This is called head shadow effect. This effect is determined by angle of incidence of sound waves and is more pronounced for frequencies above 1kHz. This inter-aural attenuation both in terms of time and intensity provides clues for sound localization. (Bruns, 2021)