Personal frequency modulation (FM) systems are like miniature radio stations operating on special frequencies assigned by the Federal Communications Commission. The personal FM system consists of a transmitter microphone used by the speaker and a receiver used by you, the listener. The receiver transmits the sound to your hearing aid either through direct audio input or through a looped cord worn around your neck.Personal FM systems are useful in a variety of situations such as listening to a travel guide or book review, in a classroom lecture, in a restaurant, in a sales meeting, or in a nursing homes or senior center.
FM systems are also used in theaters, places of worship, museums, public meeting places, corporate conference rooms, convention centers, and other large areas for gathering. In this situation, the microphone/transmitter is built into the overall sound system. You are provided with an FM receiver that can connect to your hearing aid (or to a headset if you donâ€™t wear a hearing aid).
FM systems commonly work together with a userâ€™s hearing aids, although systems are also available for those with otherwise normal hearing (such as people who suffer from APD, ADHD etc.).
The Parts of an FM System
FM systems work like small radio stations. There is a small radio transmitter attached to a microphone and a small radio receiver. A parent or teacher wears the FM transmitter and microphone while the child wears the FM receiver.
The microphone is usually worn at chest level. This type is called a lapel microphone. Lapel microphones are placed about 6 inches away from the mouth to pick up the best signal. Some systems use a mouth-level microphone which is called a boom microphone. Boom microphones are placed about 3 inches away from the mouth.
In some situations, a microphone can be placed on a table to use as a conference microphone. This allows the person using the FM to hear more than one voice around the table. Some microphones can be directional. This lets the FM microphone focus on one talker in a background of high noise. There are directional microphones that can be held by the listener who points the microphone towards the person they want to hear.
The FM transmitter sends a low-power radio signal to the FM receiver. The receiver needs to be within about 50 feet of the transmitter to pick up the signal. The radio channels for FM systems have been set aside for educational use in the United States. The FM receiver gets the signal from the microphone and sends it to a personal hearing aid, cochlear implant processor or other device. Listening to the FM signal is like listening to someone talking from only 3 or 6 inches away. Different kinds of FM receivers are available. They are either worn on the body or worn at ear level. Some FM systems work without a hearing aid and others must be connected to a personâ€™s hearing aid. Ear-level receivers are the most convenient and smallest in size. They are often recommended when using FM systems at home.
Where should FM systems be used?
In the past, FM systems were only used in schools. They helped students listen in noisy and reverberant classrooms. Many pediatric audiologists now recommend that FM systems be used at home. There are ear-level receivers and lightweight microphones and transmitters that are easy to use in everyday listening situations.
There are other benefits to using FM systems at home. Home use of FM systems can give a baby or young child more consistent speech and language exposure. For example: a mother and child are both in the kitchen, but the mother is working at the stove or sink and her back is turned to the child. If the child is using an FM system he or she can easily hear what the mother is saying no matter where the mother moves. When babies start to crawl and walk, the listening distance between the child and his or her parent can change quickly. Children often do not look at a person that is speaking. They might be busy playing or exploring while people are talking to them. An FM system keeps the listening distance close no matter what the child is doing. Children report that using the FM system gives them a feeling of security when they are at a distance from their parents, such as in the grocery store or on a family outing. This may help children develop self-esteem and independence.
Many families say that using an FM system at home gives them more opportunities to interact with their child in daily activities. Some activities where FM systems work well are traveling in the car or van, visiting the zoo, playing in the park and shopping at the grocery store. The car is a difficult listening situation. There is a lot of background noise, the child cannot see the parentâ€™s face and there is a distance between the front and back seats that cannot be changed. A hearing aid alone cannot overcome all these problems. For families that spend a lot of time in the car, using an FM system provides a better communication connection between the parent and child.
Research shows that children learn a lot of language by overhearing conversations. This overhearing helps children learn new words and grows their understanding of how to use language. Children with hearing loss may miss opportunities to overhear if people are talking more than 1 meter away or if it is noisy. Using the FM with a hearing aid can give a child more opportunities to overhear some conversations. This can help grow a childâ€™s vocabulary.
Families using an FM system with older children say that it sometimes gets used as a one-way walkie-talkie or pager. In this case the system is being used for distances beyond where people with normal hearing can hear. The FM is not intended for this use and parents should be careful when using it this way. Radio transmission beyond 50 feet is not guaranteed. Parents also can forget to turn the FM microphone off during private conversations when the child is not close by. The use of a mute switch is helpful to keep from transmitting private conversations.