McCreery, Ryan W. PhD
Hearing aids have grown increasingly sophisticated, offering signal processing designed to analyze the acoustics of a listening situation and adapt to meet the needs of the listener. This adaptation often happens automatically, without input from the listener, and can include changes to the frequency response, noise reduction, directionality, or listening program.
Figure. Automatic sw...Image Tools
Automatic switching is marketed as improving ease of hearing aid use for adults, who do not have to change programs or adjust the hearing aid manually when the feature is enabled.
Figure. Ryan W. McCr...Image Tools
However, among professionals who serve children, the availability of automatic switching has created some debate over the potential benefits and limitations of the algorithms for pediatric hearing aid users.
On one hand, the ability to have hearing aids adjust without input from the child or caregiver would seem to be greatly beneficial. Conversely, there are important reasons why this feature may not be appropriate for infants and young children.
The evidence is limited, even for adults.
Hearing aid features that automatically adjust to the listening environment have only recently become available, made possible by the development of digital signal processing in the devices and subsequent advancements over the last decade.
These changes occurred so rapidly, it's often hard to remember that it wasn't long ago that the only way to adjust hearing aid programming was to use a miniature screwdriver. Given this short time frame, there has been very little research to support the efficacy or effectiveness of the features, even for adults.
In addition, the specific parameters that activate changes in the hearing aids are often proprietary and difficult to measure with clinical verification techniques, contributing to the limited nature of the evidence base for making decisions about automatic features.
Audibility for speech must be maintained.
The purpose of fitting amplification for children is to make speech audible and provide these young patients with access to their auditory environment. Some automatic features alter not only the signal process of the hearing aid, but also the frequency response of the device.
Changes in the frequency response may modify audibility in unpredictable ways, increasing the risk for over-amplification or limited audibility. If clinicians wish to provide multiple programs that automatically switch based on listening environment, the audibility of each of those programs should be assessed using probe microphone verification to determine whether audibility is affected.
If the effect of the automatic feature on audibility cannot be determined from verification, that feature should not be implemented for children.
Consider the applicability of the processing to children.
Many automatic features have been developed based on the listening needs and environments of adults. Infants and young children may violate these assumptions in important ways.
For example, directional microphones that switch the microphone sensitivity based on the spatial location of speech and noise signals in the environment may operate under the assumption that the listener is stationary. While this assumption may be true for older school-age children, it would be difficult to characterize younger children as stationary.
How these differences between adults and children influence the effectiveness of automatic features has not been evaluated. The differences should be carefully considered prior to implementing automatic features for children.
Think about alternative strategies.
Many automatic hearing aid options are designed to improve comfort or ease of listening in background noise. Such options include automatic changes to digital noise reduction and directional microphone features used when the hearing aid detects noise in the environment.
In many listening situations, remote microphone hearing assistance technologies, such as frequency-modulation (FM) or digital-modulation systems, can provide a bigger improvement in comfort and ease of listening compared with other hearing aid features.
Remote microphone technology may not be optimal for every listening environment or situation, though. Clinicians should consider a range of options to combat the negative effects of background noise, including a combination of hearing aid features and hearing assistance technology.
Understand the manufacturer default settings for children.
Hearing aid manufacturers have gone to great lengths in recent years to create child-specific recommendations for their products’ features. These default settings often apply validated pediatric prescriptive formulae and conservative feature activation strategies based on the child's age, which is entered into the programming software.
Many manufacturers have elected to limit the activation of automatic features in their pediatric default settings. However, some manufacturers maintain the availability of automatic learning features that increase hearing aid gain over time.
It is important to become familiar with what automatic features may be available in manufacturer pediatric default settings.
Some automatic features may be desirable for children.
Aspects of automatic hearing aid signal processing may present specific benefits for children who wear hearing aids.
For example, features that automatically switch the input of the hearing aid when an FM system is activated may be advantageous for children and their caregivers. In such cases, it is important for whoever is managing the hearing aids—the child, parent, caregiver, or teacher—to understand how the feature works.
Since teachers, in particular, may manage different amplification and hearing assistance technology systems, they may assume from previous experience that the FM signal has to be activated manually, highlighting the importance of specific instructions and training when new technology is provided to a child.
GREAT POTENTIAL, LIMITED EVIDENCE
Features that automatically switch in hearing aids have great potential to increase listening comfort and ease of use in a wide range of situations. However, at this time, there is limited evidence that these features are appropriate for children.
If these features are activated for children, care should be taken to ensure that speech audibility is maintained and reasonable alternatives that could provide the same benefits are not available.
© 2014 by Lippincott Williams & Wilkins, Inc.