Sophia Koh Chapter 14 - Communication & Sciences Disorders

Amplitude:

distance from top of wave to bottom (peak to valley)

• perceived as loudness

Frequency:

number of cycles per second 

• perceived as pitch 

Period:

length of time it takes to complete one cycle before repeating

To generate sound, objects require:

mass (amt of matter) & elasticity (ability to move)

Movement of object can be represented by a:

waveform (which shows amt & rate of displacement)

Simple sounds

• vibrate at a single frequency

• rarely occur in real world

• pure-tone

Complex sounds

• vibrations that contain 2 or more frequencies

• (nearly ALL sounds) (ex. speech, music, applause)  

Vibrations cause molecules…

to move & bump into other molecules

As one moves further from the sound source: 

amplitude decreases due to friction in the air 

Auditory System:

• The ear

  • Outer ~ funnels sound waves (pinna, EAM)

  • Middle ~ amplifies waves (tympanic, ossicles, eustachian tube)

  • Inner ~ turns waves into electrical impulses (cochlea, vestibule, semicircular canals)

• Auditory nervous system 

  • Auditory nerve 

  • Brainstem 

  • Auditory cortex

Loud sounds create ________ waves; soft sounds create ________ waves 

large; small 

Tonotopic define (basilar membrane):

• traveling wave, determined by amplitude & frequency of sound

• High pitches at beginning

• Low pitches at end

Hair cells: 

• inner (1 row) vs. outer (3 rows)

• shearing motion

• depolarization - mechanically gated K+ channels 

• transduction of energy 

Transduction of energy (from hair cells):

• Cranial nerve 8 → CNS (primary auditory cortex of temporal lobe) 

• Tonotopically organized 

Auditory Nerve (Vestibulocochlear) 

• 30,000 neurons 

• Afferent (cochlea → brain; sensory) vs. efferent (brain →

cochlea; protective func) 

Auditory Pathway:

(cochlea) →

• Ventral & dorsal nuclei 

• Superior Olivary Complex 

• Lateral Lemniscus 

• Inferior Colliculus  

• Medial Geniculate Body 

• Auditory Cortex (Heschl’s Gyrus)