What is an auditory function study?

What is an Auditory Function Study?

An auditory function study is a comprehensive assessment of hearing that uses multiple testing methods—including pure tone audiometry, speech audiometry, and specialized physiologic tests—to identify the nature, origin, and extent of hearing loss across the auditory pathway from the cochlea to the brainstem. 1

Core Components of Auditory Function Testing

Behavioral Audiometry (Age-Dependent)

The primary method varies by developmental age:

• Infants 6-24 months: Visual reinforcement audiometry (VRA) conditions the child to associate sounds with visual reinforcers like lighted toys 2
• Children 2-4 years: Play audiometry uses tasks like dropping blocks in response to tones 2
• Children ≥4 years and adults: Conventional pure tone audiometry with a fail criterion of >20 dB HL at one or more frequencies (500,1000,2000,4000 Hz) 2, 3

Pure tone audiometry measures air-conduction and bone-conduction thresholds at specific frequencies to determine both the degree and type of hearing loss (conductive vs. sensorineural). 2, 1

Speech Audiometry

Speech testing provides critical functional information beyond pure tones:

• Speech detection/reception thresholds: The softest level at which speech is detected 2
• Speech recognition/discrimination scores: Percentage of words correctly identified, typically using monosyllabic word lists 2, 4
• Speech understanding in noise: Assesses real-world listening ability using tests like the Matrix sentence test 5

This component is essential because pure tone thresholds alone don't predict speech understanding—patients with similar audiograms can have vastly different speech comprehension abilities. 4

Physiologic/Objective Tests

These tests don't require patient cooperation and assess structural integrity:

• Otoacoustic emissions (OAEs): Measure cochlear outer hair cell function via a probe in the ear canal 2, 6
• Auditory brainstem response (ABR): Records neurologic responses to sound via scalp electrodes, testing from cochlea through brainstem 2, 6
• Tympanometry: Assesses middle ear function and pressure 2

Critical limitation: ABR and OAEs test auditory pathway structural integrity but are NOT true tests of hearing because they don't assess cortical processing of sound—behavioral audiometry remains essential. 2, 6

Clinical Applications

Diagnostic Differentiation

Auditory function studies determine:

• Location of pathology: Cochlear vs. retrocochlear (auditory nerve) vs. central 1, 4
• Type of loss: Conductive, sensorineural, or mixed 2, 6
• Degree of impairment: Mild (20-40 dB) to profound (>90 dB) 2, 1

Special Populations

For infants in NICU >5 days, automated ABR is mandatory (not OAEs) because it detects neural hearing loss that OAEs would miss. 6

For children with risk factors who pass newborn screening, at least one diagnostic audiology assessment including ABR should occur by 24-30 months. 6

Ototoxicity Monitoring

In cancer survivors receiving platinum-based chemotherapy, serial auditory function studies track progressive hearing loss:

• Behavioral testing (pure tone audiometry) is the gold standard 2
• Distortion-product OAEs evaluate cochlear outer hair cell function 2
• ABR assesses cochlea, auditory nerve, and lower brainstem structures 2

Pure tone audiometry detects more abnormalities than ABR in ototoxicity monitoring. 2

Key Testing Principles

Ear-Specific Assessment

Insert earphones must be used whenever possible to obtain ear-specific results and detect unilateral or asymmetric hearing loss—sound field testing only assesses the better-hearing ear. 2, 3

Test Environment

Testing requires a calibrated, sound-treated room to ensure accurate threshold measurements. 2, 1

Comprehensive Battery Approach

A complete auditory function study integrates multiple test modalities because no single test provides all necessary diagnostic information. 6, 1 The combination of behavioral audiometry (functional hearing), speech testing (communication ability), and physiologic measures (site of lesion) creates a complete picture of auditory system function from peripheral to central pathways.