ENT Notes: Hearing & Hearing Loss
⸻
I. Normal Hearing
• Normal Frequency Range:
• 20 Hz – 20,000 Hz
• Most speech occurs in 250–4000 Hz
• Normal Intensity Range:
• 0 – 120 dB
• Conversation: ~60 dB
• Whisper: ~30 dB
• Pain threshold: ~130 dB
⸻
II. Types of Hearing Loss
1. Conductive Hearing Loss (CHL)
Definition: Impaired conduction of sound from external/middle ear to inner ear.
Causes:
• Wax, foreign body
• Tympanic membrane perforation
• Otitis media, otosclerosis
• Ossicular chain disruption
• Eustachian tube dysfunction
Features:
• Low-frequency hearing loss
• Air conduction affected > bone conduction
• Speech discrimination usually preserved
• Loss ≤ 60 dB HL
⸻
2. Sensorineural Hearing Loss (SNHL)
Definition: Damage to inner ear (cochlea) or auditory nerve.
,Causes:
• Presbycusis (aging)
• Menière’s disease
• Ototoxic drugs (aminoglycosides, loop diuretics)
• Acoustic neuroma
• Infections, autoimmune disorders
Features:
• High-frequency hearing loss
• Both air and bone conduction equally affected
• Speech discrimination poor
• Loss may exceed 80 dB HL
⸻
III. Clinical Tests for Hearing Loss
1. Rinne Test (512 Hz tuning fork)
Procedure:
• Place fork on mastoid → when sound stops, move in front of ear.
Interpretation:
• Normal / SNHL: AC > BC (positive Rinne)
• CHL: BC > AC (negative Rinne)
⸻
2. Weber Test
Procedure:
• Place vibrating fork on forehead or vertex.
Interpretation:
• Normal: Sound heard equally in both ears.
• CHL: Lateralizes to affected ear (less ambient noise, better internal sound perception).
• SNHL: Lateralizes to better ear (damaged ear can’t perceive the sound well).
⸻
3. Audiometry
,Parameter Conductive Hearing Loss (CHL) Sensorineural Hearing Loss
(SNHL)
Air-Bone Gap Present (air conduction is poorer Absent (both air and bone
than bone conduction) conduction reduced equally)
Bone Normal (inner ear and nerve intact) Reduced (due to damage in
Conduction cochlea or auditory nerve)
Frequencies Low frequencies (more often) High frequencies (commonly
Affected affected)
Maximum Up to ~60 dB Can exceed 80 dB
Hearing Loss
Speech Usually good, especially in quiet Poor, particularly in noisy
Discrimination environments
V. Frequency Clarification
Frequency Type Sound Examples Affected in…
Frequency Type of Sound Examples Typically
Range Affected In
Low (20– Deep, bass sounds Thunder, drum beats, male Conductive
500 Hz) voice, vowel “oo” Hearing Loss
High Sharp, crisp, high- Birds chirping, alarms, beeps, Sensorineural
(>2000 Hz) pitched sounds “s”, “f” sounds Hearing Loss
⸻
VI. Summary Table: CHL vs SNHL
Feature Conductive Hearing Loss (CHL) Sensorineural Hearing Loss
(SNHL)
Rinne Test Negative (Bone > Air) Positive (Air > Bone, normal or
SNHL)
Weber Test Lateralizes to affected ear Lateralizes to normal ear
Air-Bone Gap Present Absent
Frequencies Low frequencies more affected High frequencies more affected
Affected
Speech Usually good, especially in quiet Poor, especially in noisy
Discrimination settings environments
, Maximum Hearing Up to ~60 dB >80 dB possible
Loss
⸻
Tinnitus
“Tinnitus is ringing sound or noise in the ear. Origin of this sound is within the patient. Usually
unilateral.”
• Tinnitus refers to the perception of sound without any external source.
• The sound is generated inside the auditory system — often described as ringing, but patients
may also report buzzing, hissing, or roaring.
• It’s usually unilateral (affecting one ear), but in some conditions like noise-induced damage or
head injury, it can be bilateral.
• Causes may include:
• Sensorineural hearing loss (e.g., presbycusis)
• Noise trauma
• Ménière’s disease
• Acoustic neuroma
• Ototoxic drugs
⸻
“Types: Subjective [Only heard by the patient]. Objective [Also heard by the examiner with
the use of a stethoscope].”
• Subjective tinnitus:
• The most common type.
• Only the patient hears it.
• Often related to inner ear or cochlear pathology.
• Objective tinnitus:
• Rare.
• A sound is produced inside the body (e.g., vascular or muscular origin).
• The examiner may hear it with a stethoscope placed near the ear.
• Causes include:
• Vascular bruits (e.g., AV malformations, carotid aneurysm)
• Palatal myoclonus
⸻
Assessment of Hearing
⸻
I. Normal Hearing
• Normal Frequency Range:
• 20 Hz – 20,000 Hz
• Most speech occurs in 250–4000 Hz
• Normal Intensity Range:
• 0 – 120 dB
• Conversation: ~60 dB
• Whisper: ~30 dB
• Pain threshold: ~130 dB
⸻
II. Types of Hearing Loss
1. Conductive Hearing Loss (CHL)
Definition: Impaired conduction of sound from external/middle ear to inner ear.
Causes:
• Wax, foreign body
• Tympanic membrane perforation
• Otitis media, otosclerosis
• Ossicular chain disruption
• Eustachian tube dysfunction
Features:
• Low-frequency hearing loss
• Air conduction affected > bone conduction
• Speech discrimination usually preserved
• Loss ≤ 60 dB HL
⸻
2. Sensorineural Hearing Loss (SNHL)
Definition: Damage to inner ear (cochlea) or auditory nerve.
,Causes:
• Presbycusis (aging)
• Menière’s disease
• Ototoxic drugs (aminoglycosides, loop diuretics)
• Acoustic neuroma
• Infections, autoimmune disorders
Features:
• High-frequency hearing loss
• Both air and bone conduction equally affected
• Speech discrimination poor
• Loss may exceed 80 dB HL
⸻
III. Clinical Tests for Hearing Loss
1. Rinne Test (512 Hz tuning fork)
Procedure:
• Place fork on mastoid → when sound stops, move in front of ear.
Interpretation:
• Normal / SNHL: AC > BC (positive Rinne)
• CHL: BC > AC (negative Rinne)
⸻
2. Weber Test
Procedure:
• Place vibrating fork on forehead or vertex.
Interpretation:
• Normal: Sound heard equally in both ears.
• CHL: Lateralizes to affected ear (less ambient noise, better internal sound perception).
• SNHL: Lateralizes to better ear (damaged ear can’t perceive the sound well).
⸻
3. Audiometry
,Parameter Conductive Hearing Loss (CHL) Sensorineural Hearing Loss
(SNHL)
Air-Bone Gap Present (air conduction is poorer Absent (both air and bone
than bone conduction) conduction reduced equally)
Bone Normal (inner ear and nerve intact) Reduced (due to damage in
Conduction cochlea or auditory nerve)
Frequencies Low frequencies (more often) High frequencies (commonly
Affected affected)
Maximum Up to ~60 dB Can exceed 80 dB
Hearing Loss
Speech Usually good, especially in quiet Poor, particularly in noisy
Discrimination environments
V. Frequency Clarification
Frequency Type Sound Examples Affected in…
Frequency Type of Sound Examples Typically
Range Affected In
Low (20– Deep, bass sounds Thunder, drum beats, male Conductive
500 Hz) voice, vowel “oo” Hearing Loss
High Sharp, crisp, high- Birds chirping, alarms, beeps, Sensorineural
(>2000 Hz) pitched sounds “s”, “f” sounds Hearing Loss
⸻
VI. Summary Table: CHL vs SNHL
Feature Conductive Hearing Loss (CHL) Sensorineural Hearing Loss
(SNHL)
Rinne Test Negative (Bone > Air) Positive (Air > Bone, normal or
SNHL)
Weber Test Lateralizes to affected ear Lateralizes to normal ear
Air-Bone Gap Present Absent
Frequencies Low frequencies more affected High frequencies more affected
Affected
Speech Usually good, especially in quiet Poor, especially in noisy
Discrimination settings environments
, Maximum Hearing Up to ~60 dB >80 dB possible
Loss
⸻
Tinnitus
“Tinnitus is ringing sound or noise in the ear. Origin of this sound is within the patient. Usually
unilateral.”
• Tinnitus refers to the perception of sound without any external source.
• The sound is generated inside the auditory system — often described as ringing, but patients
may also report buzzing, hissing, or roaring.
• It’s usually unilateral (affecting one ear), but in some conditions like noise-induced damage or
head injury, it can be bilateral.
• Causes may include:
• Sensorineural hearing loss (e.g., presbycusis)
• Noise trauma
• Ménière’s disease
• Acoustic neuroma
• Ototoxic drugs
⸻
“Types: Subjective [Only heard by the patient]. Objective [Also heard by the examiner with
the use of a stethoscope].”
• Subjective tinnitus:
• The most common type.
• Only the patient hears it.
• Often related to inner ear or cochlear pathology.
• Objective tinnitus:
• Rare.
• A sound is produced inside the body (e.g., vascular or muscular origin).
• The examiner may hear it with a stethoscope placed near the ear.
• Causes include:
• Vascular bruits (e.g., AV malformations, carotid aneurysm)
• Palatal myoclonus
⸻
Assessment of Hearing
