Study Guide

301 Study Guide – Quiz 3

Cumulative Quiz with emphasis on SNHL
High-level thinking skills will be emphasized including reading graphs, analysis, synthesis, and evaluation of outer, middle and inner ear anatomy and physiology in normal and disordered systems.
Reading: chapters 1, 3, 4 and 10 in Pickles
Articles: Diseases of the Middle Ear, Felder Scrott-Fisher (Quant eval of myelinated fibres; Qfactor?.),
Response growth with sound level in ANF with NIHL, Hearing Disorders and Audiogram Interpretation

*Know at least the main point of the peer-reviewed articles (i.e. the gap which the knowledge addresses)

The Pressure Wave (~5 points)
1. Know the difference between rarefaction and compression wave
  1. rarefaction - the state of negative air pressure
  2. compression - the state of positive air pressure
  3. a sound wave produces compression and rarefaction of the air, the molecules of which vibrate around their mean positions.
2. Link sound wave to sine wave
  1. the variations of the pressure, velocity and displacement of the air molecules in a sinusoidal sound wave are seen at one moment of time. The variations are plotted as a function of distance.
  2. the sound wave is defined by its peak amplitude and by its frequency.
3. Know parts of the pressure wave relate to loudness, frequency
  1. the extent of the pressure variation (amplitude) has a subjective correlate in loudness
  2. the frequency, or number of waves passing a point in a second, has a subjective correlate in pitch
4. Determine frequency from a sine wave graph
  1. The frequency from a sine wave graph is determined by cycles per second or Hertz (Hz)
5. Convert between period and frequency
  1. period is the time it takes to complete one cycle; period = 1/frequency
  2. frequency is the number of waves to pass any one point in a second; frequency = 1/period
Outer Ear (~5 points)
1. Be able to describe the Outer ear functions
  1. The outer ear (pinna/auricle) collects sound waves over the large area of the pinna and concha and funnels them into the narrower canal of the meatus
  2. The meatus funnels the sound to the tympanic membrane
  3. Together with the resonance in the external ear, this increases the pressure at the tympanic membrane which vibrates in response to sound pressure waves, which in turn increases the energy transfer to the middle ear
    1. 2.5kHz peak is provided by a resonance combination of the meatus and concha
  4. It aids sound localization by altering the spectrum of the sound, in a way that depends on the direction of the source
  5. there is a change in gain associated with elevation localization, there are dips around 10kHz and 20kHz that change in frequency with elevation
Describe what a Fourier transform is, what a sine wave is
1. Fourier transform is a mathematical computation that takes many sinusoids and adding them together to make a complex wave
Identify the quadrants and landmarks of the TM (label figures)
1. anterior/superior, anterior/inferior (cone of light), posterior/superior, posterior/inferior
2. Identify the structures of the temporal bone (remember your Skull Handling sheet!)
  1. *see below
3. Label the structures of the Pinna
  1. helix
  2. antihelix
  3. tragus
  4. antitragus
  5. concha
  6. lobe
  7. superior & inferior crus
  8. pyramidal/triangular fossa
  9. external auditory meatus
  10. intertragic notch
4. Read an HRTF
  1. how the ear receives a sound from a point in space. As sound strikes the listener, the size and shape of the head, ears, ear canal, density of the head, size and shape of nasal and oral cavities, all transform the sound and affect how it is perceived, boosting some frequencies and attenuating others. Generally speaking, the HRTF boosts frequencies from 2 - 5 kHz with a primary resonance of +17 dB at 2,700 Hz. But the response curve is more complex than a single bump, affects a broad frequency spectrum, and varies significantly from person to person.
Middle ear (~10 points)
1. Label anterior wall, landmarks on the ossicles, stapedius muscle
  1. promontory
  2. stapedius is attached to the stapes
2. Describe Transformer Ratio (pressure ratio, lever-to-force conversion, overall increase in dB)
  1. ratio of the areas of the tympanic membrane and oval window coupled with the lever action of the ossicles increases the force and decreases the velocity; pressure of the stapes footplate is increased 18.75 times with an overall increase in dB
3. Apply the ME Transfer and Efficiency function to the shape of Noise Induced Hearing Loss audiogram
  1. Noise Induced Hearing Loss reduces efficiency
4. Relate tympanometry to ME function/pressure in OM/otosclerosis/normal ears
  1. tympanometry assesses middle ear function and graphically displays its function
  2. A; normal shows admittance at normal pressure
  3. Ad; floppy TM or large canal volume
  4. As; rigid TM or ossicles
  5. B; flat
  6. C; negative pressure
5. Read the equal loudness contour graph and link transformer ratio, transfer and efficiency function to its shape
Cochlea (~15 points)
1. Anatomy of 3 views of cochlea, scalae, organ of corti (labeling)
  1. Describe the Endolymphatic potential and how it is generated
2. Organ of Corti
  1. Describe how OHCs are motile (prestin/stereocilia kick)
  2. Relate the motility of the OHCs to the Cochlear Amplifier
  3. Describe how the traveling wave is nonlinear
  4. Describe how the gain of the cochlear amplifier changes with sound intensity
  5. Apply genetic anomalies that affect hearing to the function of the Stria Vascularis
Auditory Nerve (~10 points)
1. Compare and Contrast OHC/IHC innervation pattern. How does this impact hearing?
2. Compare and contrast hearing loss that affects OHCs, IHCs and the Auditory nerve.
3. Define the tonotopicity pattern of auditory nerve
4. Describe how the auditory nerve is an excitatory only system “all or nothing”
5. Define Phase locking. How does this wok for simple and complex sounds?
6. Read a neural histogram graph
SNHL (~20 points)
1. Evaluate the following disorders and analyze the anatomy/physiology of the OE, ME, IE and AN:
  1. OM - otitis media, swelling, pressure variation, fluid in middle ear
  2. Otosclerosis - ossifying of ossicles which limits movement
  3. Neuroma/Blastoma - retrocochlear tumor which impinges on VIIIth nerve complex
  4. NIHL - noise induced hearing loss, loud noise that effects specific region
  5. Ototoxicity - caused by a variety of drugs; aminoglycocides, loop diuretics, salicylates, etcetera which damage hair cells
This section will be a combination of multiple choice and essay

Mastoid process of temporal bone

Zygomatic process of the temporal bone

Squamous part of the temporal bone

Anterior wall of the middle ear

Sound waves travel in a longitudinal direction, relative to the sound source.
Define areas of compression and rarefaction in a pressure wave and describe how they are created:
1. The ambient pressure exerted by the weight of the atmosphere is defined as atmospheric pressure and molecules are typically at rest unless disturbed by an external force such as the physical vibrations from a struck tuning fork. The emanating sound waves exert a force on these static molecules which increases the air pressure relative to ambient atmospheric pressure and then decreases the air pressure. The molecules continue to oscillate back and forth until the sound is dampened and quieted. These fluctuating changes in air pressure are mathematically described as a sinusoidal wave form.
2. Positive air pressure from a sound wave, denoted as an increase in amplitude from relative start position to a maximum and then a return to origin of the sine wave is known as compression. Compression displaces the air molecules rightward until maximum displacement is reached and then returns to it's original, starting position before reversing direction due to inertia
3. When the molecule reaches the origin upon it's directional reversal from rightward displacement, it continues passed it's origin in the leftward direction until it reaches it's opposite maximum position and then returns again to it's relative origin. This leftward motion is negative air pressure, denoted as a decrease in amplitude on the sine wave to it's relative negative maximum and then another return to its static origin. This process is known as rarefaction.
4. The process of compression and rarefaction oscillates until the sound is dampened and ultimately quieted, forcing the molecules to displace to the right and left of its original position due to the physical property of inertia.
In terms of a sound wave, define "one cycle."
1. One cycle of a sound wave is defined as one complete replication of a vibratory pattern or using the defined terms in question 2, one complete replication of compression and rarefaction. An undisturbed molecule at atmospheric pressure is displaced positively to the right to a maximum until it changes direction moving passed it's origin and displacing negatively to the left to a maximum and then changes direction again until it reaches it's point of origin.
What features of the sound wave relate to loudness perception, pitch perception and timbre perception?
1. The feature of a sound wave that relates to loudness perception is the frequency or rate at which the vibration of sound occurs, the feature that relates to pitch perception is the duration or time that it takes for a sound to take on a tonal quality and timbre perception is distinct from loudness and pitch as it describes the distinguishable characteristics of a tone. Timbre is mainly determined by the harmonic content and dynamic characteristics of a sound.
High pitch = high frequency. Low pitch = low frequency
1. dorsal; top or upper side
2. anterior; front or forward
3. superficial; lying at or near the surface
4. ventral; bottom or underside of the body
5. superior; at a higher position or location
6. posterior; rear or trailing end of the body
7. deep; lying away from the surface
8. medial; lying on or near the midline
9. distal; lying away from the point of attachment
10. inferior; at a lower position or location
11. proximal; lying nearer the point of attachment
12. cranial; pertaining to the head
13. caudal; pertaining to the tail
14. lateral; away from the midline
Why is it important to know how long the bony portion of the ear canal is? How will you use this in your practice?
1. The primary function of the ear canal/external auditory meatus (EAM) is to serve as a conduit for sound waves to reach the tympanic membrane so that they may be ultimately be transduced into neural cod. The lateral third of the EAM is composed of elastic cartilage and the the medial two thirds of the EAM is composed of bone. The gradation between cartilage and bone is called the isthmus and is the narrowest portion of the EAM. There are considerable differences in EAM anatomical morphology across the human population, however the approximate length is 2.4cm/24mm. It is important to know how long the bony portion of the EAM is to account for the occlusion effect (OE), the blockage or closing of the ear canal, when testing hearing by placing inserts or fitting hearing aids. The occlusion effect is minimized when contact with the bony portion of the EAM is made due to it's rigidity.
Describe the location of the stapes using anatomical terms and the landmarks of the cochlea and tympanic membrane.
1. The stapes is a small, stirrup-shaped bone that is a member of the ossicular chain (malleus, incus & stapes) and transmits vibrations from the incus to the cochlea. the stapes is located in the middle ear, an air-filled space within the petrous portion of the temporal bone, medially, slightly superior and distally to the tympanic membrane and laterally, slightly inferior and proximal to the cochlea.
Describe how we extract elevation cues from pinna reflections. What range of frequencies are best for hearing elevation cues? Why?
1. Elevation cues are measured by the medial/sagittal plane which begins at 0° when the head is facing forward in anatomical position and proceeds in a semi-circular arc to 90° vertically and then rear of the head opposite of 0° and 180° making all sounds equal distances from both ears. The auditory cortex of the brain processes these differences and computes an elevation direction along the medial plane somewhere between 0° and 180°.
2. The main function of the pinna in hearing is to localize sound by modifying it depending on the direction of the source. High frequencies are best for hearing elevation cues because the pinna will more easily attenuate or weaken the level of differences of sounds whereas the level of difference of low frequencies are not as complex making it more difficult for the pinna to attenuate and subsequently aid the auditory cortex to analyze a direction.
The frequency of a sound with a period of 10s is 0.1Hz
1. the period is the inverse of frequency measured in seconds; 1/10 = 0.1Hz
The frequency of a sound with a period of 10ms is 100Hz
1. the frequency is the inverse of the period measured in seconds, 10 ms is 0.01seconds, 1/0.01 = 100Hz
The frequency of a sound with a period of 500ms is 2Hz
1. the frequency is the inverse of the period measured in seconds, 500ms is 0.5 seconds, 1/0.5 = 2Hz
The frequency of the earth's rotation around the sun is 30nHz
1. The earth rotates around the sun once every 365 days or 8760 hours or 525,600 minutes or 31,535,000 seconds, 1/31536000 = 0.00000003s or 30nHz
The period of a sound with a frequency of 1.4Hz is
1. The period is the inverse of frequency measured in seconds, 1/1.4 =0.714s
The period of a sound with a frequency of 250Hz is 4ms
1. The period is the inverse of frequency measured in seconds, 1/250 = 0.004s or 4ms
The period of a sound with a frequency of 18000Hz is 55.56us
1. The period is the inverse of frequency measured in seconds, 1/18000 = 0.00005556 or 55.56us
The period of a sound with a frequency of 1.2Khz is 833.33us
1. The period is the inverse of frequency measured in seconds, 1/1200 = 0.000833 or 833us

1. External Acoustic Meatus 2. Mastoid process 3. Tympanic Part 4. Apex of Pyramid 5. Mandibular Fossa 6. Zygomatic Process 7. Suprameatal Spine

1. Helix 2. Triangular Fossa 3. Auricular Tuburcle 4. Scaphoid Fossa 5. Concha 6. Antihelix 7. Posterior Auricular Sulcus 8. Lobe 9. Antitragus 10. Intratragic notch 11. External Auditory Meatus 12. Tragus 13. Supratragic tubercle 14. Anterior Notch 15. Crus Helix 16. Crura of Antihelix