Audiology Week 12

Welcome back to class, continuing from Week 11.
Discussed the first quiz, awaiting results.
Mentioned makeup quizzes from last week.
Engaged the classroom with anecdotes from the weekend regarding Doppler effects.

Mentioned a personal encounter at Dave's Hot Chicken involving hearing the Doppler effect with passing cars.
Engagement with classmates about experiences; encouraged to visualize physics concepts in real-life scenarios.

Introduced a local art installation and encouraged exploration of physical phenomena.

Reminder of topics covered: wavelength, frequency, phase, and beats.
No questions asked from students about the previous week’s material, prompting further explanation.

Described a personal experiment with recording guitar sounds using Adobe Audition.
Highlighted how the proximity of frequencies affects auditory perception:
- Far Apart Frequencies: Rapid amplitude fluctuations.
- In Tune Frequencies: Reduced fluctuations, approaching harmony.
Discussed the numerical relationship between fluctuations and frequency differences:
- Use of equation: $ext{Frequency Fluctuation} = |f_1 - f_2|$ .

Defined Helmholtz resonator as a common physical model:
- Involves blowing across the top of a bottle, creating sound vibrations through trapped air.
Explained the mechanics of oscillation as analogous to a mass-spring system:
- Air in the neck as mass.
- Air in the body of the bottle as the spring.
Demonstrated effects of changing water levels on pitch:
- Drinking water lowers pitch due to increased air mass.
- Adding water raises pitch due to reduced air mass.
Connected the example to vehicle acoustics involving open windows.

Introduced tuning forks as sound production tools, vibrational mechanics illustrated:
- Physical wiggling of tines translates to sound waves.
Historical context: Previously utilized in audiology for hearing tests (placement and sensor location).

Explained the concept of decibels as a logarithmic measure of sound pressure, introduced by Alexander Graham Bell.
Softest perceivable sound defined as 20 µPa.
Explained logarithmic nature where every increase in decibels results in a tenfold change in pressure sensitivity.

Described sound level meters: instruments that measure sound pressure using a microphone to provide numerical readings.
Detailed practical application on upcoming laboratory work using sound level meters.

Discussed safe sound exposure limits and their relationship with decibel levels:
- Sound exposure time halves for every increase of 5 dB.
- Noted increased risk of hearing loss beyond 90 dB (e.g., power tools, concerts, firearms).

Introduced the three sections of the auditory system: outer ear, middle ear, inner ear.
- Outer Ear: Pinna and auditory canal function in sound collection.
- Middle Ear: Contains the eardrum and ossicles (malleus, incus, stapes) that convert sound pressure into mechanical vibrational energy.
- Inner Ear: Processes sound signals via the cochlea and auditory nerve.

Pinna: Visible part of the ear that aids in sound direction.
External Auditory Canal or Meatus: Pathway through which sound waves travel.
Clarified ear landmarks:
- Concha: Center bowl-like area of the ear.
- Tragus: Cartilage flap at the ear opening.
- Helix: Outer curved ridge.
- Antihelix: Ridge opposite to helix.
- Antitragus: Little bump near the tragus.

Sound localization: Ear shapes funnel sound waves for determination of source location.
Vertical sound localization: The shape of the ear helps in locating sounds above or below.
Directional amplification: The ear shapes enhance certain frequency ranges (3-8 kHz).

Adult ear canals measure approximately 2.5 cm.
Sections:
- Cartilaginous Portion: Flexible external part supports ear structure.
- Osseous Portion: Bony inner part covered by thin skin.
Ear Canal Shape: S-shaped curve affects sound transmission.
- Cerumen (Earwax): Natural protector that traps dirt and moisture, created for ear health.

Described how each ear collects sound waves through structure and directs them into the canal.
Mentioned physical discomfort associated with stimulation of the inner canal.

Differentiated between monaural cues (one-ear sound reception for vertical location) and binaural cues (two-ear sound reception for horizontal location).
Explained inter