I studied principally the mechanics of the middle ear, summarizing the anatomy and the physiology of the ear. I made Diagram I showing the anatomical structure of the ear, and translated it into physical terms of Diagram II, such as mass, spring, and frictional constant. etc. Thereafter I could get equations showing the mechanics of the middle ear through the Lagrangian equation. The complicated treatment for the kinetic, potential, and dissipation energies of the middle ear elements is for the purpose of expressing my opinion about the function of the middle ear which is partly different from the present contradictory medical views. By using the resultant equations of the motion of the ear and Diagram III (showing the electromechanical structure of the middle ear), I studied the mechanism of the middle ear under an assumption that the frequency characteristic curve of the inner ear is flat in a wide range. This assumption may be deduced from Luscher's experiment of the tympanic loading and hearing curves of men with complete defect of the tympanic membrane but with cochlear nerve intact. However, I do not explain it here, and it will be described in detail in further papers. From theoretical results thus obtained I made some experiments and calculation of the natural frequencies of the middle ear elements.My conclusions are as follows: (a) The air vibration system of the ear which consists of the external auditory canal, the tympanic cavity, and the antrum can be shown electromechanically by Diagram III. (b) The middle ear has four main peaks of resonance on the hearing curves. (c) The middle ear and cochlea appear to be regarded as a displacement receiver and a pressure receiver, respectively. (d) The tympanic membrance has two important roles: (1) that of composing the vibration of the external auditory canala, of the antrum, and of the air cells of the mastoid process; and (2) that of propagating these vibrations to the ossicles. (e) The non‐linear vibration of the tympanic membrane, the basilar membrane, and the secondary tympanic membrane, produce combination tones. (f) The air vibration system has an important role in understanding speech sounds. Its magnification of the sound intensity is above 50 db in a range from 700 or 800 cycles to 5000 cycles as in Fig. 5a. (g) This work offers a problem of design of a new audiometer, and is available for diagnosis of otological pathology.