Hearing aids keep getting better. But hearing aids alone do not make listening easier in all situations. The things that can interfere with listening are background noises, distance from a sound and reverberation or echo. People with normal hearing also have problems hearing when listening from a distance. Background noise and echo are a problem for everyone. People with hearing loss have even more problems than people with normal hearing when trying to listen in these difficult situations.
Babies and young children are listening in difficult situations every day. Some examples are listening in the car, at day care, playing outside or at the park, and watching television. The best way to hear better in all of these situations is to remove background noise and to have a short distance between the speaker and the listener. Most people do not talk with each other while they are standing 3 to 6 inches apart. You could not talk this closely in a car or while your child was playing at the park. Background noises usually cannot be removed or changed. Because of this, there are devices designed to make it easier to hear in difficult situations. The device used most often today is the Frequency Modulated or FM system.
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.
Different Microphone Types and Positions
Lapel microphone - about six
inches away from the mouth
Boom microphone - three
inches from the mouth
Different Types of Transmitters
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 person's hearing aid. Ear-level receivers are the most convenient and smallest in size. They are often recommended when using FM systems at home.
Integrated Ear-Level Receivers
The benefits of using an FM system are shown in the following sound examples.
In the first example “Without FM”, the teacher is giving directions, but when other students talk at the same time, the level of the teacher’s voice is too quiet to hear clearly.
In the second example “With FM”, the FM microphone is active and the teacher’s voice remains loud enough to hear, even when other students are talking.
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 parent'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 child'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.
Operating the FM System
Parents need to decide when and how the FM system should be used. There are different settings to choose from when an ear-level FM receiver is connected to the child's hearing aid.
The settings are:
Hearing aid only, with no signal from the FM microphone
FM only, with no signal from the hearing aid
Hearing aid and FM on together
The FM microphone should be turned on when the parent is talking to the child in a noisy situation. It also should be turned on when the parent is going to be at a distance from the child, but wants the child to hear her voice at a stable level. The hearing aid microphone usually stays on so that the child can hear other sounds and voices around them. When the hearing aid is on, the child also can hear his own voice. FM operation is controlled by a switch on the FM receiver or by remote control.
Buying an FM system for home use is an additional expense beyond personal hearing aids. An FM package, including the transmitter/microphone and ear-level receivers may cost around $2,500. If extra warranties or special microphones are needed, the cost may be higher. Parents often look for financial help to buy an FM system. Insurance policies often do not cover FM systems. Families should work with their audiologist and hearing aid dispenser to find funding.
For further information on FM products, look on the following websites: