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Audiology

The science of hearing, balance, and related disorders, including the assessment, diagnosis, and rehabilitation of hearing loss.

Anatomy of Hearing

Anatomy of Hearing is an essential biology topic covering living systems, from cellular processes to ecosystems.

Key points: Structure and function, clinical presentation, diagnostic criteria, and evidence-based management.

Types of Hearing Loss

Types of Hearing Loss is a clinical topic covering pathophysiology, diagnosis, evidence-based treatment, and patient care.

Key points: Core principles, practical applications, and advanced concepts that build deep understanding.

Audiometric Testing

Audiometric Testing is a clinical topic covering pathophysiology, diagnosis, evidence-based treatment, and patient care.

Key points: Core principles, practical applications, and advanced concepts that build deep understanding.

Hearing Aids

Hearing Aids is a clinical topic covering pathophysiology, diagnosis, evidence-based treatment, and patient care.

Key points: Core principles, practical applications, and advanced concepts that build deep understanding.

Cochlear Implants

Cochlear Implants is a clinical topic covering pathophysiology, diagnosis, evidence-based treatment, and patient care.

Key points: Core principles, practical applications, and advanced concepts that build deep understanding.

Balance Disorders

Balance Disorders is a clinical topic covering pathophysiology, diagnosis, evidence-based treatment, and patient care.

Key points: Core principles, practical applications, and advanced concepts that build deep understanding.

Pediatric Audiology

Pediatric Audiology is a clinical topic covering pathophysiology, diagnosis, evidence-based treatment, and patient care.

Key points: Core principles, practical applications, and advanced concepts that build deep understanding.

Tinnitus Management

Tinnitus Management is a clinical topic covering pathophysiology, diagnosis, evidence-based treatment, and patient care.

Key points: Core principles, practical applications, and advanced concepts that build deep understanding.

Key Formulas & Equations

Decibel (dB): dB = 10 × log₁₀(I/I₀) (intensity); dB = 20 × log₁₀(P/P₀) (pressure)
dB SPL (Sound Pressure Level): dB SPL = 20 × log₁₀(P/20 μPa)
dB HL (Hearing Level): Relative to normal hearing threshold
dB SL (Sensation Level): Above individual's threshold
Pure Tone Average (PTA): PTA = (500 Hz + 1000 Hz + 2000 Hz) / 3
Speech Reception Threshold (SRT): Lowest level at which 50% of spondees are recognized
Word Recognition Score (WRS): Percentage of words correctly repeated
Most Comfortable Level (MCL): Subjective loudness rating
Hearing Loss Classification (dB HL):
Normal: -10 to 15 dB HL
Slight: 16-25 dB HL
Mild: 26-40 dB HL
Moderate: 41-55 dB HL
Moderately Severe: 56-70 dB HL
Severe: 71-90 dB HL
Profound: 91+ dB HL
Acoustic Impedance: Z = ρc (density × speed of sound)
Acoustic Reflex Threshold: 70-100 dB HL (ipsilateral and contralateral)
Otoacoustic Emissions (OAEs): Present = normal cochlear function
ABR (Auditory Brainstem Response): Wave V latency = 5.5-6.5 ms
Hearing Aid Gain: Gain = Output - Input (dB)
Real Ear Measurement: REUG = Unaided response; REAG = Aided response
Insertion Gain: IG = REAG - REUG
NAL-NL2: Prescription formula for hearing aid gain

Core Concepts

Anatomy of Hearing

The auditory system: outer ear (pinna, canal), middle ear (ossicles, tympanic membrane), inner ear (cochlea, auditory nerve), and central auditory pathways.

Types of Hearing Loss

Conductive (outer/middle ear), sensorineural (cochlea/auditory nerve), mixed (both), and central (brain processing). Each has different causes and treatments.

Audiometric Testing

Comprehensive hearing evaluation: pure tone audiometry, speech audiometry, tympanometry, acoustic reflexes, and otoacoustic emissions.

Hearing Aids

Devices that amplify sound for people with hearing loss. Types include BTE, ITE, IIC, and CIC. Digital signal processing improves sound quality.

Cochlear Implants

Electronic devices that bypass damaged hair cells to directly stimulate the auditory nerve. For severe-to-profound sensorineural hearing loss.

Balance Disorders

Conditions affecting the vestibular system: BPPV, Meniere's disease, vestibular neuritis, and labyrinthitis. Treated with vestibular rehabilitation.

Pediatric Audiology

Hearing assessment in children: newborn hearing screening, behavioral observation, visual reinforcement, and play audiometry.

Tinnitus Management

Treatment of ringing in the ears: sound therapy, tinnitus retraining therapy (TRT), cognitive behavioral therapy (CBT), and hearing aids.

Worked Examples

Example 1: Pure Tone Average

Problem: Thresholds: 500 Hz = 20 dB, 1000 Hz = 25 dB, 2000 Hz = 30 dB. Calculate PTA.

Solution:

PTA = (20 + 25 + 30)/3 = 25 dB HL

Interpretation: Slight hearing loss (16-25 dB HL)

Example 2: dB Calculation

Problem: Sound pressure is 100 times reference pressure. Calculate dB SPL.

Solution:

dB SPL = 20 × log₁₀(100) = 20 × 2 = 40 dB SPL

Example 3: Hearing Loss Classification

Problem: A patient has PTA of 65 dB HL. Classify the hearing loss.

Solution:

65 dB HL = Moderately severe hearing loss (56-70 dB HL)

Practice Problems

Problem 1

Calculate PTA for thresholds: 30, 35, 40 dB HL.

Answer: PTA = (30 + 35 + 40)/3 = 35 dB HL (mild hearing loss)

Problem 2

Calculate dB SPL for pressure 10× reference.

Answer: dB SPL = 20 × log₁₀(10) = 20 dB SPL

Problem 3

Classify hearing loss for PTA = 80 dB HL.

Answer: Severe hearing loss (71-90 dB HL)

Problem 4

Identify the normal range for acoustic reflex threshold.

Answer: 70-100 dB HL

Problem 5

Calculate insertion gain if REAG = 50 dB and REUG = 30 dB.

Answer: IG = 50 - 30 = 20 dB

Problem 6

What does absent OAEs indicate?

Answer: Cochlear (outer hair cell) dysfunction

Problem 7

Calculate dB for intensity 1000× reference.

Answer: dB = 10 × log₁₀(1000) = 30 dB

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