Prescriptive Target Proximity in Children with Hearing Aids

By Kathryn B. Wiseman

This article is a part of the January/February 2022, Volume 34, Number 1, Audiology Today issue.

Hearing aid verification confirms that hearing aids provide the optimal amplification to each patient, making it an essential part of initial hearing aid fitting and follow-up care. Performing regular verification is particularly necessary when working with children who use hearing aids because children with hearing loss need consistent, audible auditory input to support speech and spoken language development (Koehlinger et al, 2013; Tomblin et al, 2015; Walker et al, 2015). 

While audiologists use several methods to verify hearing aids in children, the best method to verify a hearing aid fitting is to use a probe-microphone system to ensure hearing aid output levels match prescriptive targets in response to soft, average, and loud speech (American Academy of Audiology, 2013). 

Prescriptive targets are recommended hearing aid output levels, based on a child’s hearing thresholds and ear-canal acoustics. Clinical guidelines direct pediatric audiologists to fit hearing aids to validated prescriptive targets (Ching et al, 2013) such as the National Acoustic Laboratories, Non-Linear, version 2 targets (NAL-NL2) (Keidser et al, 2011) and the Desired Sensation Level, version 5.0 targets (DSL v5.0) (Scollie et al, 2005). 

These targets help audiologists determine whether the fitting is appropriate for a given child or if the amount of amplification should be adjusted. Children’s hearing aids need regular verification via probe-microphone measures because, as children grow, changes to the size and shape of their ear canals affect the sound level produced by the hearing aids in their ears. Performing verification using the fit-to-target metric for each child ensures their access to speech at appropriate levels as they continue to develop.

Research supports the importance of fitting hearing aids to meet prescriptive targets in children. Studies provide evidence that children with hearing aids who are fitted closer to target have better aided audibility (McCreery et al, 2015), better speech-perception outcomes (McCreery et al, 2017), and better language growth (Tomblin et al, 2015) relative to children with less proximal fittings. There is less research, however, on how to apply this knowledge to our own clinical-fitting practices.