Using Behavioral Observation Audiometry to Evaluate Hearing in Infants from Birth to 6 Months

Key Points

  • Auditory brainstem response (ABR), auditory steady state response (ASSR) and otoacoustic emission (OAE) testing provide critical information about the status of the auditory pathways, but are not direct measures of hearing
  • Only behavioral testing can provide a direct measure of hearing
  • When carefully performed using appropriate criteria (including changes in sucking as an indication of a response), behavioral observation audiometry (BOA) can accurately measure thresholds in infants younger than 6 months
  • ABR, ASSR, and OAE cannot be used to monitor auditory performance and benefit from technology, whereas behavioral testing can be used to monitor performance and benefit from technology
  • Non-behavioral tests are frequently used to assist in estimating peripheral hearing in infants
    • these are not tests of hearing
  • The only true tests of hearing is behavioral assessment
  • Behavioral tests permit measurement of what an infant actually perceives, so they are measures of functional hearing abilities
Early Infant Hearing Screening Programs
  • The first large-scale infant hearing screening program in the United States was a citywide hearing screening project in Denver, conducted by Marion Downs and Graham Sterritt in 1964
    • observation of eye widening, quieting, eye shifting, grimacing, head orienting, limb movement and changes in respiration

The Basics of Behavioral Observation Audiometry

  • Behavioral observation testing is intended as a threshold technique
  • This protocol uses observation of sucking responses and is appropriate only for infants who are cognitively at birth to 6 months of age and who are capable of sucking

What is being observed?
  • ​arousal, limb movement, respiration changes, facial grimace, eye blink
  • sucking responses however, although present at suprathreshold levels, are frequently observed at, or close to, threshold

How does one know that the sucking is a response to a sound stimulus?
  • timing is they key factor

Positioning the infant
  • appropriately positioning the infant cannot be overstated
  • most important factor in obtaining accurate test results with behavioral observation audiometry
  • To obtain reliable tests results, the infant needs to be resting in a comfortable position with full support of the head and torso and must be visible to the testers

The role of the test assistant
  • the test assistant must be constantly monitoring the infant to be certain that the baby's head and torso are comfortably balanced to minimize or preclude fussing and straining

The role of the parents
  • The parents cannot be relied on as observers and certainly not as the primary observers

Testing protocol of Behavioral Observation Audiometry

  • It may not be necessary to obtain ear-specific information at the first visit

Test stimuli
  • The goal of the testing is to obtain frequency-specific test results
  • Warble tones or narrow bands of noise will provide this information
  • Narrow bands of noise are frequently easier for an infant to respond to and may provide thresholds that are 5 to 10 dB softer than those obtained with warble tone
  • Speech awareness thresholds to low (ba (500Hz)) mid-high (sh (2000Hz)) and high (s (3-4000Hz)) frequency speech stimuli can be used to confirm warble tone/noise band thresholds

Presentation of Test stimuli
  • Many normal-hearing infants respond better to high-frequency stimuli, so it is reasonable to begin a high frequency, usually 2000Hz
  • Several indications can clue the audiologist about which frequencies and intensities should be used to begin testing
    • observe the infant's responses to noisemakers
    • observe the infant's responses to voice and environmental sounds
    • question the parents about the infant's response to sound before testing
  • Presentation of stimuli should begin at a soft level slightly above where you expect the infant to respond and then should be increased in 10dB steps until a response is observed

Behavioral Observation Audiometry Test Protocol

  1. Bring infant into test room in hungry state
  2. Seat infant so torso is supported and infant is not fidgety, and so tester(s) can easily see mouth
  3. Monitor infant state during testing and stop if infant becomes fidgety
  4. Instruct parents not to respond to test stimuli or responses from the child
  5. Test assistant will keep infant centered, observe responses and monitor parents' behavior
  6. Begin testing in soundfield
  7. Begin testing with a stimulus that is slightly above estimated threshold
  8. Test one low (500Hz) and one high (2000Hz) frequency initially and select additional frequencies to test depending on initial responses
  9. Reduce thresholds in 10dB steps and increase in 5 to 10 dB steps to bracket threshold. Record a response after three reversals
  10. Take breaks as needed to calm the infant and increase usable test time
  11. If soundfield testing indicates a hearing loss, test bone conduction
  12. If infant is still responding, or at the next test session, test with insert earphones
  13. Test with technology as needed

Adding Objectivity to Behavioral Observation Audiometry

The Test Setting

Infant State and Positioning
  • "State" refers to the infant's level of arousal, from deep sleep to hysterical crying

Movement of Test Assistant and Parent/Caregiver
  • Be still and non-responsive to the test stimuli
  • Keep the infant focused at midline
  • Be reminded not to respond to the stimulus by altering the movement of the toy or facial expressions