Transcript Hearing
Hearing Subtitle I CAN • Explain the sensation process as it applies to hearing using the anatomically correct terms The Physics of Sound Frequency: The number of cycles a Amplitude: sound wave completes the Strength in a given period of time of a wave Anatomy of the Ear From Sound Wave to Perception 1. Pinna Tympanic Membrane (eardrum) bones of inner ear (hammer, anvil, stirrup) COCHLEA (primary hearing organ) 2. Cochlea is filled w/ fluid, which further transmits vibrations to thin membraneBasilar Membrane 3. BM = Transduction; tiny hairs on BM tickle the sensory nerves 4. Neural message is sent to Temporal Lobe How Sound Waves Become Auditory Sensations Tympanic membrane – The eardrum Copyright © Allyn and Bacon 2006 How Sound Waves Become Auditory Sensations Cochlea – Where sound waves are transduced Copyright © Allyn and Bacon 2006 How Sound Waves Become Auditory Sensations Auditory nerve – Neural pathway connecting the ear and the brain Copyright © Allyn and Bacon 2006 3 Psychological Sensations of Sound 1.Pitch- the way we sense frequency 2.Loudness- the way we sense amplitude 3.Timbre- the way we sense the complex mix of tone Copyright © Allyn and Bacon 2006 Theories of Hearing • Place theory – Pitch (how high or low something is) is determined by location of vibration along the basilar membrane – But this doesn’t explain low-pitch since we haven’t found specific positions for those on the bm • Frequency theory – Pitch is determined by frequency hair cells produce action potentials – If the frequency of the sound is 100 waves per second then the neuron fires at 100 pulses per second. – But we can hear frequencies above 1000 waves per second but can’t fire neurons faster than 1000 pulses per second. – Volley Principle • Pattern of sequential firing creates a combined high frequency signal Localization of Sounds Because we have two ears, sounds that reach one ear faster than the other ear cause us to localize the sound. Conduction Deafness • An inability to hear resulting from damage to structures of the middle or inner ear • Conductive hearing loss is often only mild and is never worse than a moderate impairment. • Generally, with pure conductive hearing loss, the quality of hearing (speech discrimination) is good, as long as the sound is amplified loud enough to be easily heard. • Possible Causes • Ear wax build up • Fluid inside the inner ear, like from an inner ear infection. • If the bones of the ear get a buildup of calcium Sensorineural Deafness… or Nerve Deafness • An inability to hear, linked to a deficit in the body’s ability to transmit impulses from the cochlea to the brain, usually involving the auditory nerve or higher auditory processing centers • It can be mild, moderate, severe, or profound, to the point of total deafness. • Possible Causes • Long-term exposure to environmental noise • Genetic • Disease or illness • Medications • Physical trauma Pre-Lingual Deafness • These are people that are born deaf CAN I? • Explain the sensation process as it applies to hearing using the anatomically correct terms