3 - Bone Conduction Flashcards
True or False: On a bone conduction Oscillator, the maximum output levels are restricted by the amount of energy needed to drive the oscillator
True
What are the 3 modes of transmission for bone conduction?
Osseotympanic
Inertial
Distortional/Compressional
Normal patients take advantage of all 3 modes of bone conduction transmission. Which one do patients with conductive loss take advantage of?
Distortional/Compressional
Describe how osseotympanic bone conduction transmits sound to the cochlea
- BC oscillator vibrates bones of the skull
- Skull vibrations radiate into the ear canal (converted to acoustic air vibrations)
- Air vibrations transmitted to cochlea via typical air conduction route
With osseotympanic bone conduction, ___ (high/low) frequencies are transmitted through the cartilaginous walls of the ear canal, by the condyloid process (mandible)
Low
With osseotympanic bone conduction, ____ (high/low) frequencies are transmitted to the EAM by other cranial bones (besides the mandible)
High
Inertial bone conduction stimulation dominates in the ____ (high/low) frequencies
Low
_______ (Osseotympanic/Inertial/Distortional or Compressional) bone conduction works by setting the ossicular chain in motion, although there is a lag in their movement, relative to the rest of the skull
Inertial
Placement of the bone conductor at the forehead results in NO ______ (Osseotympanic/Inertial/Distortional or Compressional) bone conduction, because the skull moves forward/back, which is opposite to the direction of ossicular motion
Inertial
________ (Osseotympanic/Inertial/Distortional or Compressional) bone conduction is more dominant in the high frequencies
Distortional/Compressional
The _________ (Osseotympanic/Inertial/Distortional or Compressional) mechanism of bone conduction works by distortion of the inner ear structures by compression of the skull bones
Distortional/Compressional
True or False: The Osseotympanic mechanism of Bone Conduction causes vibration of the bony labyrinth and membranous structures and fluid, which stimulates the hair cells
False; Distortional/Compressional Bone conduction does this
What is the term used to describe the phenomenon of increased perception of sound (especially low frequencies) when one or both ears are covered?
The Occlusion Effect
What frequencies are commonly tested during BC?
250, 500, 1000, 2000, 4000
What are two factors that may interfere with BC (false positive, false negative)?
- Vibrotactile threshold (felt not heard)
- Environmental noise (e.g. chewing gum, not in a sound booth, etc)
What are the two types of placement for BC?
Mastoid and Forehead
Name one advantage for each type of BC placement
Mastoid: -larger dynamic range -may be more sensitive -tactile sensation less likely Forehead: -don't need to move headphones for masking -eliminate inertial BC mechanism
Name one disadvantage for each type of BC placement
Mastoid:
- poor placement can affect threshold result
- placement may slip
Forehead:
- reduced dynamic range
- greater likelihood of tactile sensation rather than true hearing threshold with severe to profound hearing loss
True or False: Individuals may experience anywhere from 0-15 dB HL of interaural attenuation
True
True or False: “Crossover” refers to how BC can stimulate both cochleae
True
If crossover results in only finding threshold of the cochlea with the best hearing sensitivity, how do we test each ear separately?
Masking
Vibrotactile threshold rather than true BC thresholds can occur at:
_____ dB at 250 Hz
55 dB at ______ Hz
____ dB at 1000 Hz
25, 500, 70
Describe why sounds seem louder when one or both ear canals are covered (e.g. during BC testing)
- osseotympanic mechanism of bone conduction
- low frequency sounds normally escape through open ear canal, but cannot escape when ears are covered
