Ask Linn: FM Options
Question: My 7-year-old daughter is a bilateral cochlear implant recipient who received her first implant when she was one year old and the second one this summer. We would like information about FM options that will allow her to hear with both implants.
That is a very good question! With school starting soon, I am sure there are many parents of Nucleus® recipients who are concerned about providing the best listening environment for their children in the classroom. Whether your child hears with one or two ears, there are a number of assistive listening technologies that can help improve their hearing in difficult listening environments like classrooms.
Noise has greatest impact on children during the period of language acquisition. Assistive listening systems are necessary for individuals with hearing loss to hear their best in difficult listening environments like classrooms. Distance from the sound source and background noise can make it extremely difficult to hear, and children are especially vulnerable.
There are several things to consider when choosing an assistive listening system. The age of the child and the length of time they have used their cochlear implant are both important when deciding on the type of system to use. FM systems require more monitoring by a hearing person to ensure that the system is working correctly and the child is not experiencing interference that can affect sound quality. Very young children or those who have used their implants for a very short time are unable to provide adequate feedback about what they are hearing.
What's best for you?
Soundfield System:
Another type of assistive listening system, called a Soundfield system, is sometimes chosen for those who are too young or inexperienced with their cochlear implants to give good feedback.
Soundfield systems consist of a two main parts: a transmitter /microphone, similar to the transmitter and microphone used for an FM system, and a speaker used by the listener.
Where the Soundfield system differs from FM is on the receiving end. Soundfield systems use a speaker, and depending on the model being used, can be installed in the classroom ceiling, on a stand or placed on a table at ear level directly in front of the student using the system.
Students who change classrooms throughout the day sometimes use a portable Soundfield system that can be carried by the student from class to class. The advantage of Soundfield for very young or inexperienced implant users is that the sound can be constantly monitored by the classroom teacher so if there is a problem with the system, it can be readily identified and corrected without much effort. Since the teacher’s voice is projected through the speaker, some also find that they don’t have to raise their voices as much to keep order in the classroom. Nothing is connected to the cochlear processor and a bilateral recipient can hear with both ears.
The disadvantage of Soundfield is that they typically provide only 10-15 decibels of advantage over the level of background noise compared to 20-30 decibels of advantage with a good quality FM system. It is also very important that the speaker be placed in an optimal position for the best results. If Soundfield is used in the classroom, the parent must ensure that the system is being properly used or the child may not receive much benefit.
FM Systems
Schools commonly use FM Systems that consist of three main parts
• a transmitter and a microphone worn by the teacher and
• a receiver worn by the student using the system
The more advanced FM systems operate in a special frequency range (216-217 MhZ) that is reserved for assistive listening systems. Many of these systems offer multiple channels. If there is interference or a child in a nearby classroom is using a particular channel, a different channel can be selected to avoid picking up unintended sound signals.
FM systems are frequently recommended for older children or those who have at least six months experience with their cochlear implant. The benefit of FM fitting is to
improve speech understanding by optimizing the speaker’s voice while reducing background noise. The speaker’s voice is presented at a consistent decibel level regardless of background noise, competing conversations or poor acoustics.
While the best FM systems typically provide a greater ‘signal to noise’ advantage, there are also more parts to an FM system and a hearing person must check the system to ensure it is working properly. Monitor Earphones are provided for Nucleus sound processors such as the SPrint, ESPrit 3G and Freedom. A hearing person can then listen to the sound being received by the FM system to ensure that it is working properly and there is no interference on the frequency being used. Systems like Phonak offer multiple frequencies so if there is interference on one channel, another channel can be selected.
