Language and Mind, Week 1
Language and Mind, Week 1 LING 275
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This 3 page Class Notes was uploaded by Carole Boulware on Wednesday July 20, 2016. The Class Notes belongs to LING 275 at University of Southern California taught by Elsi Miia Kaiser, Rachel Walker in Spring 2016. Since its upload, it has received 22 views. For similar materials see Language and Mind in Linguistics at University of Southern California.
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Date Created: 07/20/16
Language and Mind, Ling 275g Spring 2016, Kaiser/Walker Overview of lecture on February 23: Sound and The Ear Sound Wave • Source of vibration • Air compression and rarefaction • Displacement of air • Propagation of sound wave Rarefaction • A state or region of minimum/reduced pressure. Important aspects of sound • Cycle o One complete occurrence of a wave pattern. • Frequency o Measured in cycles per second (Hertz – Hz) o Related to perceived pitch o Humans can perceive 20–20,000 Hz • Amplitude/intensity o Related to perceived loudness • Simple sound wave o Sine wave: A waveform with periodic oscillations of constant amplitude. The ear and sound journey • External ear o Ear canal o Cavity is air-filled o Terminates at eardrum o Wave amplification o Pressure at the eardrum for amplified tones may be as much as ten times greater than at the entrance to the ear. • Middle ear o Cavity is air-filled o Bones: • hammer (malleus) • anvil (incus) • stirrup (stapes) o Eardrum makes contact with the hammer/malleus. Vibration serves to transfer air pressure into mechanical movement of bones. 1 o The series of three bones works together via lever-like action to amplify the sound signal. o Amplified signal is transmitted by contact of the stirrup/stapes at the oval window. o The amplification system of the middle ear works in such a way that pressure at the oval window is 80 times greater than it would be if the eardrum and bones were not present. • Inner ear o Fluid-filled o The inner ear has both balance and hearing functions o Semicircular canals • Responsible for maintaining equilibrium and balance o Cochlea • Coiled snail-like shape • The cochlea is where acoustic mechanical vibrations are transformed into electrical signals that can be transmitted and processed by the central nervous system o Motion of oval window causes fluid displacement – and as a result – fluid pressure changes. o Sound vibrations affect the basilar membrane • Frequency encoding by place of greatest stimulation of the basilar membrane. • Base: narrow and stiff — greater vibration for high frequencies. • Apex: wide and elastic — greater vibration for lower frequencies. o Organ of Corti • Lies atop the basilar membrane • Covered by the tectorial membrane • Contains hair cells • Mechanical vibration of regions on the basilar membrane produce hair cell stimulation – place of greatest vibration is related to frequency, degree of hair cell stimulation is related to intensity/amplitude. • Hair cells perform the transformation of mechanical activity to electrical signals that are sent out through the fibers of the auditory nerve. A handout from class provides some illustrative figures. It can be downloaded from Blackboard. Some important terms/concepts Cycle Frequency Pitch Amplitude/intensity Loudness 2 Rarefaction Sine wave External/Outer ear Middle ear; Hammer, Anvil, Stirrup Inner ear; Cochlea, Semicircular canals Basilar membrane, Organ of Corti, Tectorial membrane Hair cell Sound wave amplification by the ear How the cochlea encodes frequency and intensity/amplitude of a sound wave 3
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