Sound waves are funneled by the pinna, or auricle, into the external auditory meatus (fig. 10.17). These two structures form the outer ear. The external auditory meatus channels the sound waves (while increasing their intensity) to the eardrum, or tympanic membrane. Sound waves in the external auditory meatus produce extremely small vibrations of the tympanic membrane; movements of the eardrum during speech (with an average sound intensity of 60 dB) are estimated to be about the diameter of a molecule of hydrogen!
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This ebook provides an introductory explanation of the workings of the human body, with an effort to draw connections between the body systems and explain their interdependencies. A framework for the book is homeostasis and how the body maintains balance within each system. This is intended as a first introduction to physiology for a college-level course.