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Valentina Carlile Osteopata
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Science: Why do we hear less underwater?

Science: Why do we hear less underwater?

The mechanism used by the ear to convert sound waves in the passage from air to liquid without there being a significant loss of energy is called impedance adaptation and is achieved through the differential of the measurement between the eardrum and the foot of the stapes and the lever action of the ossicles.

Only 1% of airborne sound enters a liquid medium, while 99% is reflected. The middle ear has two ways to restrict this potential energy loss:

  • the difference in size between the eardrum and the stapes footplate: the eardrum has an effective surface area ratio that is 14 times greater than that of the stapedial footplate. This hydraulic effect increases the pressure force from the eardrum on the footplate of the stapes so that there is approximately a 23 dB increase in loudness on the inner ear fluid

  • the action of the lever of the ossicles: this lever amplifies the intensity of the sound as it passes through the middle ear by approximately 2.5 dB. Therefore, the middle ear impedance matching mechanism is not perfect, but accounts for the 25.5 dB increase in sound pressure intensity at the air-liquid interface

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