Download What happens at the hearing aid fitting?

Australian Hearing
http://www.hearing.com.au
What happens at the hearing aid fitting?
Your child’s hearing aids will be adjusted to fit neatly on their ears, and individually programmed to
optimise the hearing in each ear. Then the audiologist will show you how to use the aids and how
to help your child wear them and get used to them. See Getting used to hearing aid. [link]
How do audiologists programme hearing aids?
Audiologists follow this process to fit hearing aids:
1. Obtain reliable hearing test results that are as complete as possible, given the child’s age
and abilities. The test results are used to prescribe amplification targets.
2. Measure and adjust the hearing aids to meet the amplification targets as closely as possible
in each ear.
3. Investigate how well your child is hearing with their hearing aids. Asses if they are hearing
well, progressing with language and learning. If not, deciding what should be checked or
changed.
NAL-NL2 prescription
When an Australian Hearing audiologist fits a hearing aid, they use a complex set of formulas
known as the NAL-NL2 prescription. NAL-NL2 is based on research undertaken by Australian
Hearing’s research arm, the National Acoustic Laboratories (NAL), over 40 years ago. It remains
one of only two prescriptive procedures recommended by the 2013 American Academy of
Audiology Task Force on Paediatric Amplification.
NAL-NL2 aims to maximise speech intelligibility and to keep amplified speech comfortable at all
frequencies. The NAL-NL2 formulas prescribe just how much gain, or ‘loudness’, should be added
to soft, moderate and loud speech sounds at different frequencies. Programming a hearing aid to
meet these targets should allow the softer parts of speech to be heard while keeping the louder
sounds comfortable and clear.
When programming a hearing aid, it’s also important that very loud sounds cannot exceed the limit
of comfort for the wearer. NAL-NL2 prescribes an upper limit to the maximum output of an aid to
avoid discomfort form very loud sounds.
How will the audiologist know if the hearing aid is meeting the amplification targets?
Your audiologist uses various procedures to measure how a hearing aid is working:
Real-Ear Measurements
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Real-Ear-to-Coupler Difference (RECD) measurements
Hearing aid test box (or “coupler”) measurements.
Real-Ear Measurements (REM)
Real-Ear Measurements measure the hearing aid while it is worn in the ear. This measurement
takes account of the hearing aid and the acoustic effects of the child’s ear and earmould.
Audiologists use NAL-NL2 software to work out the REM targets for the child’s hearing loss in
each ear.
To make real-ear measurements, a headset is put on the ear and a soft thin tube is placed in the
ear canal. Then the hearing aid is put into the ear with a programming cable connected.
A short burst of sound is played from a speaker. The results are displayed on a screen and the
audiologist can make adjustments to match the targets as closely as possible.
Your child needs to sit still and quiet for REMs to be completed. If adjustments are needed, your
child may need to sit still for five to 10 minutes for each ear. This procedure is best suited to
children five years or older.
Hearing aid test box (or “coupler”) measurements
A hearing aid test box is a small, sound-treated enclosure that allows accurate, repeatable
measurements to be made of a hearing aid. Test box measurements are fast and are often used to
quickly check how a hearing aid is working in comparison to previous test box measurements.
Real-Ear-To-Coupler Difference (RECD) measurements
Young children usually can’t sit still and quietly long enough for REMS to be completed, especially
when the aids need adjustment. The RECD measurement is better for this age group because it
only needs a single measurement in each ear.
In this procedure, a sound is measured in the child’s ear with the hearing aid and ear mould in
place. The same sound is also measured with the hearing aid in a test box. The difference between
these two measurements (real-ear versus coupler) is the real-ear-to-coupler difference.
Using the RECD values, your audiologist can measure the sound in the test box and accurately
determine the level of sound in your child’s ears when hearing aids are worn. The hearing aids can
be adjusted in the hearing aid test box to achieve the best possible match to the prescription
targets.
Getting started with hearing aids
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Once the aids are adjusted to suit your child’s loss, the audiologist will show you how they operate
and help you practice putting them onto your child’s ears. They will also give you information about
helping your child get used to the aids and start wearing them consistently. For more information
see the following articles: Checking your hearing aid is working [link] and Getting used to hearing
aids. [link]
Evaluating the hearing aid’s effectiveness
At the next appointment, your audiologist will evaluate how well your child hears and progresses
with the hearing aids. Evaluation is important to ensure that your child is actually getting the
predicted real-life benefit from the hearing aids. See: Making sure your hearing aid is working. [link]
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