{"id":160,"date":"2015-02-06T23:15:46","date_gmt":"2015-02-06T23:15:46","guid":{"rendered":"https:\/\/courses.candelalearning.com\/ospsych\/?post_type=chapter&p=160"},"modified":"2024-05-17T02:30:40","modified_gmt":"2024-05-17T02:30:40","slug":"hearing","status":"publish","type":"chapter","link":"https:\/\/courses.lumenlearning.com\/waymaker-psychology\/chapter\/hearing\/","title":{"raw":"How We Hear","rendered":"How We Hear"},"content":{"raw":"
\r\n
\r\n

Learning Objectives<\/h3>\r\n
    \r\n \t
  • Describe the basic anatomy and function of the auditory system<\/li>\r\n \t
  • Explain how we encode and perceive pitch and localize sound<\/li>\r\n<\/ul>\r\n<\/div>\r\nOur auditory system converts pressure waves into meaningful sounds. This translates into our ability to hear the sounds of nature, to appreciate the beauty of music, and to communicate with one another through spoken language. This section will provide an overview of the basic anatomy and function of the auditory system. It will include a discussion of how the sensory stimulus is translated into neural impulses, where in the brain that information is processed, how we perceive pitch, and how we know where sound is coming from.\r\n\r\n<\/div>\r\n
    \r\n

    Anatomy of the Auditory System<\/h2>\r\nThe ear can be separated into multiple sections. The outer ear includes the pinna<\/strong>, which is the visible part of the ear that protrudes from our heads, the auditory canal, and the tympanic membrane<\/strong>, or eardrum. The middle ear contains three tiny bones known as the ossicles<\/strong>, which are named the malleus<\/strong> (or hammer), incus<\/strong> (or anvil), and the stapes<\/strong> (or stirrup). The inner ear contains the semi-circular canals, which are involved in balance and movement (the vestibular sense), and the cochlea. The cochlea<\/strong> is a fluid-filled, snail-shaped structure that contains the sensory receptor cells (hair cells) of the auditory system (Figure 1).\r\n
    \r\n\r\n[caption id=\"\" align=\"aligncenter\" width=\"975\"]\"An Figure 1<\/strong>. The ear is divided into outer (pinna and tympanic membrane), middle (the three ossicles: malleus, incus, and stapes), and inner (cochlea and basilar membrane) divisions.[\/caption]<\/figure>\r\nSound waves travel along the auditory canal and strike the tympanic membrane, causing it to vibrate. This vibration results in movement of the three ossicles. As the ossicles move, the stapes presses into a thin membrane of the cochlea known as the oval window. As the stapes presses into the oval window, the fluid inside the cochlea begins to move, which in turn stimulates hair cells<\/strong>, which are auditory receptor cells of the inner ear embedded in the basilar membrane. The basilar membrane<\/strong> is a thin strip of tissue within the cochlea. Sitting on the basilar membrane is the organ of Corti, which runs the entire length of the basilar membrane from the base (by the oval window) to the apex (the \u201ctip\u201d of the spiral). The organ of Corti includes three rows of outer hair cells and one row of inner hair cells. The hair cells sense the vibrations by way of their tiny hairs, or stereocillia. The outer hair cells seem to function to mechanically amplify the sound-induced vibrations, whereas the inner hair cells form synapses with the auditory nerve and transduce those vibrations into action potentials, or neural spikes, which are transmitted along the auditory nerve to higher centers of the auditory pathways.\r\n\r\nThe activation of hair cells is a mechanical process: the stimulation of the hair cell ultimately leads to activation of the cell. As hair cells become activated, they generate neural impulses that travel along the auditory nerve to the brain. Auditory information is shuttled to the inferior colliculus, the medial geniculate nucleus of the thalamus, and finally to the auditory cortex in the temporal lobe of the brain for processing. Like the visual system, there is also evidence suggesting that information about auditory recognition and localization is processed in parallel streams (Rauschecker & Tian, 2000; Renier et al., 2009).\r\n
    \r\n

    Watch IT<\/h3>\r\nWatch the process of audition in the following video:\r\n