Conductive hearing loss

Common causes of conductive hearing loss include:

• Injury of the outer ear itself
• Blockage of the ear canal due to ear wax (cerumen) or other small objects like food, beads or insects
• Infections of the outer or middle ear
• Perforation of the tympanic membrane
• Congenital deformities (e.g. Down syndrome, Franceschetti syndrome, Treacher Collins syndrome or Achondroplasia (dwarfism)

The audiogram below demonstrates conductive hearing loss. In this example, the inner ear works properly but something inhibits sound from getting through the outer/middle ear to the inner ear.

Learn how to read an audiogram

The hearing loss displayed above ranges from 30 to 50 dB HL in the right ear and between 35 and 45 dB in the left ear. This individual would only be able to perceive fragments of normal speech, which has a loudness level of about 65 dB. A normal hearing person has a dynamic range of up to 65 dB between listening threshold (at 0 dB) and speech level (at 65 dB). The person with the described hearing loss only has a dynamic range of about 20 dB. This difference of about 45 dB must be amplified to enable the person to perceive speech and sounds appropriately.

Depending on the general diagnosis, the necessary amplification is usually provided by:

• Conventional hearing instruments (sometimes not possible due to chronic inflammation, effusion and/or dysplasia of the outer ear/ear canal)
• Bone conduction hearing instruments: Behind-the-ear shell with a vibrating transducer, placed on the skull using a headband or retainer
• Bone anchored hearing aid (BAHA): A vibrating hearing solution which is attached to the skull using a screw which is implanted behind the ear

If the inner ear is unimpaired, bone conduction hearing solutions do not deliver any amplification. Their task is only to make sounds audible by an adequate vibration of the skull, which transfers the sound information directly to the inner ear. Starting from there, the hearing process continues normally.