Personal or Soundfield FM’s

Jane Madell
December 18, 2012

Australian Hearing, the organization that provides support to children and adults with hearing loss in Australia, has just written  a document comparing the benefits of different types of FM systems. This is really important information to use in deciding what kind of FM system to recommend for a child. Research has clearly demonstrated that children with normal hearing benefit significantly by using a soundfield FM system in the classroom. Similarly, studies demonstrate that children with hearing loss do NOT benefit from soundfield FMs.


FM for children with cochlear implants

A study published by Schafer and Kleineck in the Journal of Educational Audiology in 2009 conducted a meta-analysis of studies looking at benefit from different types of FM systems. They determined that traditional soundfield FM systems did not significantly improve speech recognition in noise compared to listening without an FM system. Desktop and personal FM both provided significant benefit, but personal FM provided much greater benefit. The data showed the following:

  • Benefit from personal FM over CI alone         38%
  • Benefit of Desktop FM over CI alone               17.1%
  • Benefit of soundfield  over CI alone                  3.5%

Any doubt about what we should be recommending?


Benefit of Adaptive (Dynamic) FM

The studies reviewed by Schafer and Kleineck were conducted with fixed FM receivers. These receivers have the same gain regardless of the amount of noise in the room. Newer receivers with adaptive FM adjust to the noise in the room. All the research is demonstrating that Dynamic FM provides even greater benefit than fixed gain FM systems. As a result, we should expect increased benefit. There are no published research studies on Dynamic FM yet, but the data from Phonak, which makes the Dynamic FM system, reports that in a quiet classroom the sound from the FM should be +12dB compared to the background noise and in a noisy classroom the SNR should be maintained at +10dB.


Is there a benefit of using both personal FM and soundfield FM?

While soundfield FM will provide significant benefit for children with normal hearing, there is no reason to believe that there will be any significant benefit to children with hearing loss. In fact, if the personal FM is being coupled to the soundfield system, the results can have a significant negative impact because the effects of the dynamnic FM may be lost.


So what should we recommend?

  • Children wearing hearing aids or cochlear implants should be fit with appropriate personal FM systems.
  • Soundfield FM may provide limited additional benefit.
  • Children using dynamic FM systems should NOT have them coupled to the classroom soundfield FM systems



birdsong hearing benefits

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