Paediatric Audiology Course 2018 – All credit for the content contained within this article goes to Susan Scollie from the Child Amplification Laboratory at Western University. My interpretation of the presented information may not be 100% accurate. To ensure you are getting the best and most accurate information please refer to the original source. This is for information purposes only. Please refer to our disclaimer for further details.
Hearing Aid Prescription Formula
DSL v5 Overview
Avoiding aided loudness discomfort
Ensuring audibility of conversational speech
Supporting infant hearing instrument fitting
Make a wide range of speech input levels audible
Accommodating the different needs of listener with congenital versus acquired hearing loss
Accommodating the different hearing requirements of quiet and noisy listening environments
DSL v5 points to remember
Conductive loss – DSL v5 increases the upper limit of comfort by 25% of the air-bone gap. Therefore, it is important to note that the formula is reliant on the bone conduction thresholds. Wherever possible, when applying DSL v5, audiologists should be assessing bone conduction thresholds. As well as that, they should be setting up their verification equipment to use bone conduction thresholds in the prescription settings.
Binaural fittings – DSL v5 will decrease overall gain by 3dB, without decreasing the maximum output level when it is a binaural fitting. Once again, this reinforces the importance of checking your prescription parameters when performing verification.
The OCHL study tested 317 children with hearing loss and 117 who were normally hearing from 17 states in America. It was discovered that some hearing aids were fitted well, but some were not fitting well. The research goal was to identify factors that influence children’s access to language input, and determine how these contribute to risk or to protection.
Only 65% of children had good access to speech
Only 65% of the children assessed had good access to speech at their earliest visit, and stayed that way throughout the study. This means that 35% of the children either had poor access throughout or had declining access to speech
Wear hearing aids for a minimum of 10 hours per day
Children need to wear their hearing aids for a minimum of 10 hours a day. This is to provide consistent access to speech. As well as this, the study demonstrated that those children that had early intervention performed consistently better for language scores against those that had intervention at a later age.
Late intervention mostly caught up by the age of 6 but there was still a difference in performance. This highlights the importance of our national hearing screening programme and how early intervention results in better long-term outcomes.
Probe Tube Measurements
Taking probe tube measurements allows us to take in to consideration the individual acoustics of the childs ear. Probe tube measurements can be accurate within 5dB up to 4KHz. Above this frequency the reliability of the probe tube measurement is more variable. It is important to note in the latest BSA guidelines for Probe tube measurements the depths have changed.
Adult males are now: 30mm
Adult females: 28mm
What transducer should I use?
If an insert transducer is used: Hearing Loss + Calibration + RECD= Real Ear SPL
If TDH is used: stored average values only.
Therefore use Insert earphones wherever possible when performing RECD’s and applying the DSL v5 prescription formula.
Noise management in hearing aids
Excessive loudness may be associated with fewer hours of daily hearing aid use which may limit benefit through inconsistent access to amplified sound (Humes et al, 2010)
Noise management features to consider in a paediatric fitting
Directional microphones – more than one microphone used to reduce amplification of sounds coming from non-frontal locations
Adaptive noise reduction – digital signal processing to identify and minimise unwanted noise
Frequency gain-shaping – adjustment of hearing aid gain
Automatic switching between programs
Data logging to impact on use, and the child’s exposure to situations
Recommendations for settings
Embed noise management strategy in to program 1 or an automatically activated program 2. Only add a manually accessible program if the child is able to manage and understand the use.
Routine use of adaptive noise reduction, speech enhancement, and transient noise reduction is recommended
Routine use of data logging to monitor use of different strategies is recommended
Verify Adaptive Noise Reduction (ANR)
Each manufacturer varies in the strength of ANR. You can verify ANR using a test box measurement. This feature is available in Otometrics Aurical under the ‘Noise Reduction’ tab in the PMM module. General rules to follow when running ANR testing:
Must run signal for 30+ seconds (or max allowed) to allow for ANR to activate full strength
Use speech noise (not ‘children’)
User timer and keep it consistent
Choose a level and keep it consistent unless you are probing level effects.
Recommended protocol for Noise Management
Consider candidacy factors
Consider practical factors
Verify the hearing aid without ANR
Enable noise management program
Program noise management strategy
Verify by running 75dB SPL speech into the hearing aid with and without noise management enabled (not necessary case by case, just when using a new hearing aid for first time) – both curves should be similar
Measure noise signal at 85dB for 30 seconds – consider strengthening processor if <3dB attenuation
Counsel on appropriate use and monitor outcomes.
There are many benefits recognised from the application of frequency lowering on children with hearing loss. However, for the fitting to be successful it requires objective assessment of residual hearing and individualised tuning of speech sounds to ensure audibility (Scollie & Glista, 2010). Individuals vary in the need for frequency lowering.
Validation of Frequency Lowering for children
Verify and tune the hearing aid to DSL with frequency lowering disabled – mark the lower and upper limits of the maximum audible output frequency range (MAOF)
Assess Candidacy – measure aided /s/ at 65dB SPL. Does the upper corner fall within the MAOF and/or passband? If not, frequency lowering candidacy may be a factor.
Fit frequency lowering if indicated – Tune to the weakest possible setting that moves the upper corner of /s/ into the audible passband of the device.
The following image depicts frequency lowering off. You can see the upper shoulder of /s/ (in pink) is outside of the audible range.
When frequency lowering is applied you can see the upper shoulder of /s/ sits in the region of the MAOF. This is the ideal application.
Should /s/ and /sh/ be separated in frequency?
Providing the best possible separation between these two sounds is a good way to support the listener in perceiving them as different. However, the MAOF protocol asks you to search for the weakest possible setting that provides /s/ audibility. By definition, this also maximises s-sh separation. Therefore, fine tuning with /sh/ is not necessary, but the stimulus is provided for you to use if you wish.
Aided Speech Sound Detection Tests
Ling 6 Test
Originally proposed for live voice use by therapists (Ling 1989). It is useful for:
Probing whether the child can detect all sounds across the speech frequencies.
Probing whether they can discriminate the sounds
Regular parental testing protects against hearing aid malfunction
Suggested Use Of Ling 6
Useful outcome measure for young infants – confirm reception of sound, demonstrate efficacy to parents. This does not access speech sound discrimination or identification.
Determine if hearing aid bandwidth/dsp provides access to all 6 sounds.
For fittings that can not be verified with real ear measurement, aided detection thresholds provide some information about device function.
For me, the most insightful part of the Paediatric Audiology Course 2018 was the recommended protocol for noise management. Before now, I had never considered the option of objectively measuring how we are applying noise management at first fit. The process is quick and straight forward and is certainly something that could be applied, not only for children, but for all individuals with hearing impairment. I would like to thank Audiology Planet for inviting us along today and to Susan Scollie for sharing her expertise and profound insights in to paediatric audiology.
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