3 - Bone Conduction

Question 1

True or False: On a bone conduction Oscillator, the maximum output levels are restricted by the amount of energy needed to drive the oscillator

Answer 1

True

Question 2

What are the 3 modes of transmission for bone conduction?

Answer 2

Osseotympanic
Inertial
Distortional/Compressional

Question 3

Normal patients take advantage of all 3 modes of bone conduction transmission. Which one do patients with conductive loss take advantage of?

Answer 3

Distortional/Compressional

Question 4

Describe how osseotympanic bone conduction transmits sound to the cochlea

Answer 4

• 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

Question 5

With osseotympanic bone conduction, ___ (high/low) frequencies are transmitted through the cartilaginous walls of the ear canal, by the condyloid process (mandible)

Answer 5

Low

Question 6

With osseotympanic bone conduction, ____ (high/low) frequencies are transmitted to the EAM by other cranial bones (besides the mandible)

Answer 6

High

Question 7

Inertial bone conduction stimulation dominates in the ____ (high/low) frequencies

Answer 7

Low

Question 8

_______ (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

Answer 8

Inertial

Question 9

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

Answer 9

Inertial

Question 10

________ (Osseotympanic/Inertial/Distortional or Compressional) bone conduction is more dominant in the high frequencies

Answer 10

Distortional/Compressional

Question 11

The _________ (Osseotympanic/Inertial/Distortional or Compressional) mechanism of bone conduction works by distortion of the inner ear structures by compression of the skull bones

Answer 11

Distortional/Compressional

Question 12

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

Answer 12

False; Distortional/Compressional Bone conduction does this

Question 13

What is the term used to describe the phenomenon of increased perception of sound (especially low frequencies) when one or both ears are covered?

Answer 13

The Occlusion Effect

Question 14

What frequencies are commonly tested during BC?

Answer 14

250, 500, 1000, 2000, 4000

Question 15

What are two factors that may interfere with BC (false positive, false negative)?

Answer 15

• Vibrotactile threshold (felt not heard)

- Environmental noise (e.g. chewing gum, not in a sound booth, etc)

Question 16

What are the two types of placement for BC?

Answer 16

Mastoid and Forehead

Question 17

Name one advantage for each type of BC placement

Answer 17

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

Question 18

Name one disadvantage for each type of BC placement

Answer 18

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

Question 19

True or False: Individuals may experience anywhere from 0-15 dB HL of interaural attenuation

Answer 19

True

Question 20

True or False: “Crossover” refers to how BC can stimulate both cochleae

Answer 20

True

Question 21

If crossover results in only finding threshold of the cochlea with the best hearing sensitivity, how do we test each ear separately?

Answer 21

Masking

Question 22

Vibrotactile threshold rather than true BC thresholds can occur at:
_____ dB at 250 Hz
55 dB at ______ Hz
____ dB at 1000 Hz

Answer 22

25, 500, 70

Question 23

Describe why sounds seem louder when one or both ear canals are covered (e.g. during BC testing)

Answer 23

• osseotympanic mechanism of bone conduction

- low frequency sounds normally escape through open ear canal, but cannot escape when ears are covered