SLHS 302 Final Exam

Outer Ear

Includes the pinna, ear canal, and tympanic membrane.

Pinna

Protects the ear canal, provides sound amplification, and aids in localization.

Ear Canal

Acts as a band-pass filter (resonator system) that amplifies middle frequencies.

Tympanic Membrane (Eardrum)

Cone-shaped membrane that closes the ear canal and connects to the malleus.

Distortion

Creation of new frequencies not present in the original input.

Clipping

Occurs when sound exceeds maximum amplitude, causing the wave to be cut off.

Binaural Cues

Sound localization info from both ears (ILD and ITD).

Interaural Level Differences (ILD)

Difference in sound level/intensity between ears; prominent at high frequencies.

Interaural Time Differences (ITD)

Difference in sound arrival time between ears; prominent at low frequencies.

Monaural Cues

Sound localization info from one ear, depending on sound elevation.

HRTFs (Head-Related Transfer Functions)

The outer ear's amplitude response curve used for localization.

Middle Ear

Air-filled cavity housing the ossicular chain, located in the temporal bone.

Ossicular Chain

Connects the eardrum to the oval window (Malleus, Incus, Stapes).

Malleus

Attached to the eardrum.

Incus

The middle bone ("anvil").

Stapes

Attached to the cochlea via the oval window; the smallest bone in the body.

Middle Ear Function

To transfer energy from air to fluid, overcoming impedance mismatch.

Impedance Mismatch

Difficulty of energy transformation from air (low) to fluid (high).

Area Transformer

Main mechanism for overcoming impedance mismatch (eardrum to oval window area difference).

Stapedius Muscle

Contracts during the acoustic reflex to dampen low frequency sound.

Eustachian Tube

Connects middle ear to nasopharynx to equalize air pressure.

Otitis Media

Fluid in the middle ear; causes low frequency hearing loss due to increased stiffness.

Conductive Hearing Loss

Damage to the outer or middle ear.

Cochlea

The receptor organ for hearing; transduces mechanical energy into electrical energy.

Base (of Cochlea)

Narrower, stiffer section; processes higher frequencies.

Apex (of Cochlea)

Wider, less stiff section; processes lower frequencies.

Tonotopic Organization

Cochlea is organized by frequency (high at base, low at apex).

Traveling Wave

Wave of displacement moving along the basilar membrane from base to apex.

Scala Media (Cochlear Duct)

Central chamber filled with endolymph (+80 mV potential); contains the Organ of Corti.

Endolymph

Fluid in the scala media with a high +80 mV electrical potential.

Perilymph

Fluid in the scala vestibuli and scala tympani.

Organ of Corti

Sits on the Basilar Membrane; contains Inner and Outer Hair Cells.

Inner Hair Cells (IHCs)

Sensory transducers; send 95% of information to the brain (via Type 1 afferent neurons).

Outer Hair Cells (OHCs)

The "Cochlear Amplifier"; change length/stiffness to sharpen sound (via protein prestin).

Electromotility

The ability of OHCs to extend and contract to amplify sound.

Tip Links

Protein bridges that connect stereocilia, allowing them to move as one unit.

Stria Vascularis

The "Cochlear Battery"; maintains the endocochlear potential by supplying K+.

Depolarization

Cell becomes more positive (excitation), allowing K+ in.

Hyperpolarization

Cell becomes more negative (inhibition).

Otoacoustic Emissions (OAEs)

Sounds produced by the ear, generated by OHCs; used for newborn hearing screening.

Loss of OHCs

Leads to loss of the cochlear amplifier and distorted sound.

Loss of IHCs

Causes severe/profound hearing loss because no information can be sent to the brain.

Cochlear Synaptopathy

Disconnection between IHCs and afferent nerve fibers (e.g., from noise or aging).

Sensorineural Hearing Loss

Damage to the cochlea (inner ear) or auditory nerve.

audibility

detecting sound

intelligibility

understanding sound

tinnitus

ringing in the ears

sound waves

acoustic

vibrations

mechanical

neutral signals

bio-electric

sound

vibration of an object that causes oscillation of a medium through which energy propagates

elasticity

the ability of a mass to return to its natural shape

inertia

property to resist change

acoustical signals

variations in air pressure

mechanical signals

variations in position (displacement)

electrical signals

change in voltage

period

amount of time to complete one cycle

frequency

cycles per second

amplitude

amount of displacement

root means squared amplitude

0.707 A

phase

what is the displacement at a given time (radians)

friction

decreased motion over time; amplitude gradually decreases, frequency not impacted 

pressure

force per unit area

node

where the wave hits zero

antinode

peak amplitude of the wave

condensation

region of high density and high pressure

rarefaction

region of low density and low pressure

speed of sound

350 m/s

sound pressure doubles

+ 6 dB

pressure increase by factor of 10

+ 20 dB

intensity doubles

+ 3 dB

intensity increase by factor of 10

+ 10 dB

power

rate at which energy is transformed by a wave

inverse square law

intensity is inversely related to distance

see exponential decrease as distance increases

distance doubled

6 dB decrease

absorption

sound energy is taken in by materials and converted into heat

anechoic room

designed to have no sound

reverberation time

time for reduction by 60 dB

reflection

sound bounces off a surface

interference 

interaction of 2+ waves 

constructive interference

two waves in phase; add to create larger sound pressure

destructive interference

two waves out of phase; add to make less sound pressure

reverberation

persistence of a sound in an enclosed space

standing wave

stable patterns of interference caused by reflections 

sound shadow

area where there is little sound

complex sounds

what we hear in the real world

pure tone

single sine wave

fundamentals frequency 

lowest frequency of a complex sound 

octave

doubling a frequency

periodic wave

a waveform that repeats over time

aperiodic wave

a waveform that does not repeat over time; have infinite period

transience 

brief pulse in music

beats

small frequency difference between f1 and f2

fourier’s theorem

any complex wave is a sine waves

fourier analysis

decomposition of a wave

fourier synthesis

reconstructing a wave

amplitude modulation

change in amplitude over time

frequency modulation

bandwidth over which the signal changes

SAM tones

2 sine waves multiplied together

gaussian noise

instantaneous amplitude probability follows a normal curve