WAEC - Biology (1995 - No. 22)
The following are directly involved in transmission of sound waves to the brain except
eardrum
auditory meatus
auditory ossicles
eustachian tube
cochlea
Explication
More specifically, the Eustachian tube permits equalization of pressure in the middle ear for ambient pressure. In doing so, the Eustachian tube allows for the regulation of the pressure across the tympanic membrane. It thus influences the tension in this structure and the attached ossicles, and in this way indirectly affects the effectiveness of sound wave transmission.