Exam 3 Study Guide

Exam 3 Study Guide - Exam 3 Study Guide Auditory System...

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Exam 3 Study Guide Auditory System Adapted to capture vibrations Speed of sound through air = 340 m/s (depending on humidity) o Through water = 1500 m/s What is sound? o Amplitude (intensity) Loudness, measured in Db Db = difference between 2 sounds in terms of the ratio between sound pressures Small Db changes can correspond w/ lg physical changes Greater amplitude of movement Amplitude is doubled, frequency is the same Greater frequency of movement Amplitude same, frequency doubled o Frequency Wavelength # of cycles/sec – Hz Perceptually = pitch o Tuning fork is one of the only ways you can hear a pure tone Pure tone = sine wave Air pressure in the wave changes continuously Period = on complete cycle of a sine wave Not common sounds Most sounds are complex sounds o Human hearing uses a limited range: 20-20,000 Hz Dogs/cats are higher Dolphin = 150kHz o Timbre The quality of a sound depending upon relative energy levels of harmonic components Outer Ear o Pinna External ear Only mammals have one Enhances and captures tones Some better for capturing, others for localizing o External auditory meatus Ear canal Extends about 25mm into the head Length and shape enhance sound frequencies Main purpose is to insulate the eardrum from damage Middle Ear o Tympanic membrane Ear drum Separates external auditory meatus from inner ear Sometimes people get tubes put into their ears through the membrane and the slits made to insert the tubes can heal with a lot of scar tissue causing damage to hearing Thin sheet of skin that moves in and out in response to pressure changes of sound waves Border between outer and middle ear o Ossicles Smallest bones in the body
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Amplify sound vibrations in 2 ways Joints between the bones work like levers, so a modest amt of energy on one side becomes larger on the other Concentrate energy from a larger to smaller surface area Amplify movement/sound from tympanic membrane Malleus, incus, stapes (hammer, anvil, stirrup) Malleus – connected to eardrum and incus on the other o Tensor tympani = muscle connected to malleus o Tense when sounds are very loud, restricting movement of ossicles, muffling pressure changes that might be damaging to delicate structures in the inner ear - Can also tens e during swallowing, talking, a nd g en eral body m ov e m ent Incus – conn ect ed to m alleus and stap es Stap es – conn ect ed to incus an d trans mits vibrations to oval window o Stap edius = m uscle att ach ed to stap es o Tense wh en sounds are very loud, restricting m ov e m e nt of ossicles, m uffling pressure ch ang es th at might b e d a m aging to d elicat e structures in th e inner e ar - Can also tens e during swallowing, talking, a nd g en eral body m ov e m ent Moving/vibrating o Oval window Sep arat es mid from inner e ar Pressure is 18x th at of e ardru m o Round window
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