This document defines different types of hearing loss including conductive, sensorineural, and mixed. It describes the magnitude, type, and configuration of hearing loss. Normal hearing is defined as thresholds ≤15 dB. Degree of loss is categorized as slight, mild, moderate, etc. based on puretone average. Conductive loss shows normal bone conduction but abnormal air conduction with an air-bone gap. Sensorineural loss has equal abnormal air and bone conduction thresholds. Mixed loss has characteristics of both. Configuration can be flat, rising, sloping, or precipitous. Certain conditions require medical referral.

1. Ozarks Technical Community College

2. Hearing Loss is defined by…
 Degree/Magnitude of Loss
 Normal, slight, mild, moderate, moderately-severe,
severe, profound
 Type of Loss
 Conductive
 Sensorineural
 Mixed
 Configuration of Loss
 Flat, rising, sloping, precipitous

3. Normal Hearing
 Normal AC and BC
thresholds (≤15 dB)
 Many different scales
exist regarding degree
of hearing loss
 For the purposes of
this class, we will use
the scale on the next
slide.

4. Degree of Hearing Loss
 This is the exact scale that I
use in interpreting
audiograms
 Some clinics are more liberal
and consider normal hearing
to be any threshold up to 25
dBHL
 In determining the degree of
loss, the textbook approach
would be to calculate the
puretone average
(PTA=average dB of AC
thresholds at .5, 1, 2 kHz) and
compare the PTA to the scale
at right.
From: Northern, J. Hearing Disorders (3rd ed)

5. Audiometric Interpretation
 If a patient has a disorder of the outer and/or middle
ear ONLY, then AC thresholds will be abnormal in the
presence of normal BC thresholds
 Air-bone gap = greater than or equal to 15dB difference
between AC and BC
 This is called a conductive hearing loss (CHL), as
sound cannot properly conduct through the outer
and/or middle ear to reach the normal-hearing
cochlea

6. Some Causes of CHL
 Anotia
 Microtia
 Atresia
 Outer ear infection
 Middle ear infection
 Otosclerosis
 Dislocation of the middle ear bones
 Cholesteatoma
 Ear wax!

7. Conductive Hearing Loss
 Normal BC thresholds
 Abnormal AC
thresholds
 An air-bone gap is
present at .5, 1, 2, and
4 kHz
 WRS should be nearly
normal, as there is no
damage to the
cochlea/nerve Image from: telemedicine.orbis.org
This patient has a mild CHL

8. Collapsing Canals
 If you ever discover a conductive hearing loss
component in the high frequencies when you are using
traditional headphones, it is necessary to retest your
air-conduction thresholds using inserts.
 The pressure of traditional headphones can actually
cause a collapse of the ear canal in some patients
(especially true in the elderly)

9. Audiometric Interpretation
 If a patient has a disorder of the inner ear and/or
auditory nerve, then AC thresholds will be equal to BC
thresholds (no air-bone gap) and both will be
abnormal
 This is called a sensorineural hearing loss (SNHL)

10. Some Causes of SNHL
 Aging (presbycusis)
 Noise Exposure
 Genetics
 Acoustic Neuroma
 Meniere’s Disease
 Ototoxic Drugs

11. Sensorineural Hearing Loss
 Abnormal AC and BC
thresholds
 No air-bone gap
 WRS will vary depending
on degree of loss and
cochlear vs. neural
damage
 According to the PTA
method of determining
degree of HL, this patient
has a slight SNHL.
 However, due to the
sloping configuration, it is
more accurate to define
the loss as a slight-
sloping-to-severe SNHL.
Image from: telemedicine.orbis.org

12. Puretone Audiometry Interpretation
 If a patient has a disorder of the inner ear and/or
auditory nerve AND an outer/middle ear disorder,
then both AC thresholds and BC thresholds will be
abnormal AND an air-bone gap will exist
 This is called a mixed hearing loss (MHL)
 Example: 75 yo, male with age-related hearing loss and
bilateral otitis media

13. Mixed Hearing Loss
 Abnormal AC and BC
thresholds
 Air-bone gap present
 Expected WRS based
on BC thresholds
 This patient has a
mild to moderately-
severe MHL.
Image from: telemedicine.orbis.org

14. Configuration of HL
 Flat
 Thresholds within 20dB of each other across all frequencies
 Rising
 Low frequency thresholds are at least 20dB poorer than high
frequencies
 Sloping
 High frequency thresholds are at least 20dB poorer than low
frequencies
 Precipitous
 High frequency thresholds worsen by at least 20dB per octave

15. Always keep these FDA Regulations
in mind…
 If any of the following conditions exist, a patient must be
referred for a medical evaluation by a physician (preferably
an ENT):
 Visible congenital or traumatic deformity of the ear.
 History of active drainage from the ear in the previous 90
days.
 History of sudden or rapidly progressive hearing loss within
the previous 90 days.
 Acute or chronic dizziness.
 Unilateral hearing loss of sudden or recent onset within the
previous 90 days.
 Audiometric air-bone gap equal to or greater than 15 decibels
at 500 Hz, 1,000 Hz, and 2,000 Hz.
 Visible evidence of significant cerumen accumulation or a
foreign body in the ear canal.
 Pain or discomfort in the ear.