Hearing Aid Choices FM Systems 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 Microphones 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 Receivers 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 persons hearing aid. Ear-level receivers are the most convenient and smallest in size. They are often recommended when using FM systems at home. 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.
Posted on: Fri, 14 Nov 2014 05:54:14 +0000
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