Outer Ear
• Pinna = outside portion of the ear, focuses sound waves on the eardrum (tympanic membrane)
• External auditory canal = ear canal, leads to the eardrum, contains ceruminous glands that secrete earwax
Middle Ear• Sound vibrations from the
eardrum pass to auditory ossicles (three tiny bones – malleus/hammer, incus/anvil, & stapes/stirrup) which transmit sound to the inner ear
• Eustachian tube connects to pharynx, allowing air pressure to equalize on both side of the eardrum; can be blocked by infections
The Inner Ear• Cochlea filled with
fluid picks up vibrations from middle ear which cause hair cells in cochlea to bend
• Movement of hair converts vibrational energy into nerve impulses
Auditory Pathway
Vestibulocochlear nerve VIII takes the information to medulla oblongata and then to auditory cortex in the temporal lobe
Sound Levels of Common NoisesSound
IntensityNoise Source
60 db Normal conversation, bird song
80 db Heavy traffic, ringing phone
85 – 90 db Motorcycle, snowmobile
90 db Hair dryer, lawn mower
95 – 105 db Hand drill, bulldozer, spray painter
110 db Chain saw
120 db Ambulance siren, rock concert
140 db Jet engine at takeoff
165 db Shotgun blast
Safe range
Risk range
Injury range