Sound transmission in the human auditory system
The main purpose of the peripheral auditory system is to transform sound stimuli to a neural representation in the auditory nerve that can be unambiguously interpreted in the auditory cortex and by the cognitive system. The neural coding itself is done by the sensory cells in the inner ear, but the whole system of outer, middle, and inner ear, and even the skull itself is responsible for the sound energy to elicit the inner ear sensory cells. Sound transmission is categorized as air conduction and bone conduction, where air conduction is the normal route to the inner ear involving the sound transmission in the ear canal, motion of the ear drum and middle ear ossicles, that finally result in a sound pressure in the inner ear fluid that drives the basilar membrane and excites the sensory cells. Bone conduction transmits the sound in a complex manner to the inner ear and also results in in a sound pressure in the inner ear fluid. However, its drive of the basilar membrane and excitation of the sensory cells are not equally clear. Even so, bone conduction sound transmission is important as it is used to classify the origin of a hearing loss, it limits the maximum attenuation for hearing protection devices, is used for rehabilitation of persons with hearing loss, and is used for communication, especially in extreme environments. The talk will illustrate the sound transmission pathways in the human using a model based approach.