ABA Transmission & Drivetrain Systems 3 — Questions and Answers
Question 1: In tympanometry, a Type Ad (deep) tympanogram pattern most likely indicates which transmission problem?
- Otosclerosis with stapes fixation
- Eustachian tube dysfunction with negative pressure
- Ossicular discontinuity or hypermobile tympanic membrane (Correct answer)
- Sensorineural hearing loss
Correct answer: Ossicular discontinuity or hypermobile tympanic membrane
A Type Ad tympanogram shows abnormally high compliance (deep peak), indicating a highly mobile system such as ossicular discontinuity or a flaccid tympanic membrane.
Question 2: Which frequency range is most attenuated by the acoustic reflex's stiffening effect on the ossicular chain?
- High frequencies (>4000 Hz)
- Mid frequencies (1000–2000 Hz)
- Low frequencies (<1000 Hz) (Correct answer)
- Ultra-high frequencies (>8000 Hz)
Correct answer: Low frequencies (<1000 Hz)
The stiffness introduced by acoustic reflex contraction primarily attenuates low-frequency transmission because stiffness reactance is dominant at lower frequencies.
Question 3: The Carhart notch, a characteristic audiometric dip around 2000 Hz on bone conduction, is associated with which drivetrain pathology?
- Cochlear hydrops
- Otosclerosis (Correct answer)
- Noise-induced hearing loss
- Presbycusis
Correct answer: Otosclerosis
The Carhart notch is a mechanical artifact of otosclerosis where stapes fixation reduces the resonant contribution of the ossicular chain to bone conduction testing.
Question 4: What is the approximate total middle ear transformer gain that compensates for the impedance mismatch at the air-fluid interface?
- 10–15 dB
- 25–30 dB (Correct answer)
- 40–45 dB
- 50–60 dB
Correct answer: 25–30 dB
The combined area ratio and ossicular lever action provides approximately 25–30 dB of gain, offsetting the ~30 dB loss that would otherwise occur at the air-fluid interface.
Question 5: Cholesteatoma most commonly damages transmission by eroding which ossicle?
- Malleus manubrium
- Long process of the incus (Correct answer)
- Stapes footplate
- Anterior malleal ligament
Correct answer: Long process of the incus
The long process of the incus is the most common site of erosion by cholesteatoma due to its relatively poor blood supply, causing ossicular discontinuity.
Question 6: Which probe tone frequency is recommended by ASHA guidelines for tympanometry in neonates to assess middle ear transmission?
- 226 Hz
- 678 Hz
- 1000 Hz (Correct answer)
- 2000 Hz
Correct answer: 1000 Hz
A 1000 Hz probe tone is recommended for neonates because the neonatal ear canal and middle ear are mass-dominated at low frequencies, making 226 Hz unreliable.
Question 7: The term 'acoustic immittance' encompasses both acoustic impedance and its reciprocal. What is the reciprocal of impedance called?
- Admittance (Correct answer)
- Compliance
- Conductance
- Reactance
Correct answer: Admittance
Acoustic admittance (Y) is the reciprocal of acoustic impedance (Z), and modern tympanometry measures admittance because it is more clinically useful.
ABA Transmission & Drivetrain Systems 3
In tympanometry, a Type Ad (deep) tympanogram pattern most likely indicates which transmission problem?