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LESSON 165

Visual reinforcement audiometry

Year 2
Spring semester
Pediatric Audiology
Pediatric assessment
Duration: 12:00

This lesson covers visual reinforcement audiometry (VRA), used with children aged about 6 to 24 months. With examples, we explain the conditioned head turn response, visual reward and conditioning, control trials, and ear-specific testing with insert earphones.

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Hello, and welcome to the AIHEAR Audiology Academy.
In this lesson we will learn visual reinforcement audiometry, or VRA.
We will cover the conditioned head turn response, control trials and ear-specific testing with insert earphones.
Visual reinforcement audiometry, or VRA, is a behavioral hearing test developed for young children.
When the child hears a sound, they turn their head toward the reward box; this is called a conditioned head turn.
A head turn made at the right time is rewarded by showing a lit or moving toy.
The method is based on operant conditioning: a rewarded behavior becomes more likely to be repeated.
The method has its roots in the conditioned orientation reflex technique described in the 1960s.
The lowest response levels obtained in infants are often called minimal response levels.
VRA is usually used with children aged about six to twenty four months.
What matters is developmental rather than chronological age; for premature babies, corrected age is used.
The child needs to be able to control their head and sit with support.
Because the reward is visual, the child's vision must be good enough to notice it.
Some guidelines suggest it up to a developmental age of about thirty months; many children move to play audiometry around age two.
The child sits in the test room, usually on a parent's lap, facing forward.
The reward box and loudspeaker are placed to the child's side, often at an angle of about ninety degrees.
A distracter in front of the child keeps the child's gaze at the center with quiet toys.
The stimulus is given through a loudspeaker in the sound field or, if the child accepts them, through insert earphones.
The tester controls the audiometer, presents the stimulus and judges the response.
When the type of loss needs to be understood, bone conduction responses can also be obtained with a bone vibrator.
The tester sets the timing and level of the stimulus and decides whether a response is valid.
The distracter holds the child's attention at the center without over-entertaining; a very exciting game can reduce head turns.
The parent is asked to stay quiet and not to signal to the child when they hear the sound.
To prevent unintentional cues, some centers give the parent masking sound through headphones.
In some systems, test and control trials are scheduled and recorded by computer, which reduces observer bias.
The reward is often a toy that lights up and moves inside a dark box, or a short video clip.
The reward is given only after a correct response made at the right time.
Keeping the reward brief delays the child's habituation to it.
When interest fades, switching to a different toy or image can revive responses.
The reward must not make a sound that could be confused with the test stimulus, or the child may respond to the wrong sound.
The test starts at a clearly audible level that the child is sure to hear.
In the first trials the sound is presented and the reward is lit right after it, linking sound and reward.
After a few trials, the child starts turning their head on hearing the sound, without waiting for the reward.
This head turn before the reward shows that conditioning has taken place.
Usually, threshold searching begins after two or more consecutive correct responses.
If the loss is severe, a higher level or vibration from the bone vibrator can be used for conditioning.
Threshold searching uses frequency-specific stimuli, such as warble tones with a slightly modulated frequency, or narrowband noise.
After a response the level is lowered, after none it is raised; for example, ten decibels down and five up near threshold.
Only head turns made within a short time window after the stimulus are accepted as responses.
The reward is kept brief and changed if needed, so the child's interest lasts longer.
Because the child will tire after a certain number of responses, the most important frequencies are tested first.
Usually one low and one high frequency are targeted in each ear first, followed by the frequencies in between.
VRA can be done with speech sounds as well as tones, giving the speech awareness level.
The Ling sounds, m, oo, ah, ee, sh and s, cover a wide range from low to high frequencies.
These sounds are especially useful for checking aided hearing in children who wear hearing aids.
However, speech is a broadband stimulus, so it does not replace frequency-specific thresholds.
So responses to speech are used to complement the findings obtained with tones.
Now let us look at a purely example VRA result; for this child, testing was done with insert earphones.
In the right ear, responses were obtained at around twenty to twenty five decibels at all frequencies.
In the left ear, however, responses rose to fifty and sixty decibels at two thousand and four thousand hertz.
Had this test been done in the sound field, the right ear would have responded and this left ear loss would have been missed.
This finding needs to be evaluated together with ABR, OAE and tympanometry.
Control trials are observation trials in which no sound is presented at all.
In these trials, you check whether the child turns their head at random even without sound.
Head turns on control trials are not rewarded; otherwise the child is conditioned to timing rather than to sound.
If the false response rate is high, for example above thirty percent, the levels are unreliable and the child is reconditioned.
Control trials are placed at irregular intervals among the real trials.
The report also states the false response rate and the reliability of the test.
If stimuli come in a regular rhythm, the child may turn by predicting the timing, so the intervals are varied.
If the distracter knows when the stimulus is presented, they may give cues without realizing it.
So it is preferable that the distracter neither hears nor sees the stimulus.
What counts as a response, for example a clear head turn toward the reward, is clearly defined before testing.
These precautions ensure that the results come from the child's hearing, not from the observer's expectations.
A clinical tip: if the child accepts them, start the test with insert earphones from the very beginning.
Sound field responses reflect only the better-hearing ear and can hide a unilateral loss.
Foam-tipped insert earphones are well tolerated by most children and can be fitted during the distraction play.
Because the child's attention is limited, getting ear-specific information from the first responses makes testing more efficient.
Sound field testing is a useful start for children who will not wear earphones.
However, the result reflects the two ears hearing together, in practice the better ear.
Insert earphones allow each ear to be tested separately and reveal a unilateral or asymmetric loss.
Because interaural attenuation is high with insert earphones, there is also less need for masking.
To avoid standing waves in the sound field, warble tones or narrowband noise are preferred over pure tones.
If air conduction responses are elevated, VRA with bone conduction can be done to understand the type of loss.
The bone vibrator is placed on the mastoid, taking care that it does not slip as the child moves.
If bone conduction responses are normal and air conduction responses elevated, a conductive component is considered.
Because bone-conducted sound reaches both cochleae, without masking you cannot know which ear responded.
Middle ear fluid is common in this age group, so evaluation together with tympanometry is important.
Over time the child habituates to the reward and responses decline, so the information from one session is limited.
For children with developmental delay or vision problems, the method may not be suitable or may need adapting.
Even in infants with normal hearing, minimal response levels may be slightly higher than adult thresholds.
So results are interpreted with ABR, OAE and tympanometry findings, following the cross-check principle.
When needed, testing is completed over several sessions and the consistency of results is monitored.
This information forms the basis for hearing aid fitting, if needed, and for the follow-up plan.
The report states clearly whether testing was done in the sound field or ear-specifically with earphones.
The stimulus type used and the frequencies tested are recorded.
Along with the response levels, the false response rate on control trials and overall reliability are noted.
Details such as the child's alertness, cooperation and why testing stopped early help plan the next session.
Sound field results are shown on the audiogram with the sound field symbol, not with ear-specific symbols.
VRA suits children with a developmental age of about six to twenty four months.
The child is conditioned to turn toward sound, and correct responses are reinforced with a visual reward.
Control trials without sound show random head turns and the reliability of the test.
Because the sound field reflects only the better ear, ear-specific testing with insert earphones is the goal.
Test yourself: in VRA, what is the purpose of control trials presented without sound?
The correct answer is B: to measure random head turns, that is, false responses.
If the false response rate is high, the levels obtained are not considered reliable.
In the next lesson we will learn conditioned play audiometry, or CPA, used with older children.
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Prerequisites

LESSON 164 Behavioral observation audiometry

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