The text makes a comment in passing that the sensitivity of

The text makes a comment in passing that the sensitivity of hearing would be 15-20 dB less if the tympanic membrane and ossicular system were missing. Based on your know ledge of the biomechanics of the middle car, can provide any quantitative support for this statement? dB is a relative power representation, where dB = 10log(Power_2/Power_1). Note that the power of a sound wave is proportional to the square of the sound pressure.

Solution

Middle ear transfers the vibrations of the eardrum into waves in the fluid and membranes of the inner ear. The primary function of the middle ear is to balance the declined acoustic energy due to low impedance ear canal air which directly contacted the high-impedance cochlear fluid. When a sound wave is transferred from a low-impedance medium like air, to one of high impedance (eg, water), a considerable amount of its energy is reflected and fails to enter the liquid. If no middle ear were present, only 0.1% of the acoustic wave energy traveling through air would enter the fluid of the cochlea and 99.9% would be reflected. Any dysfunction or disease of the components of middle ear results in a conductive hearing loss, and clinically, an individual’s inability to properly hear sound.