What is an FM System?

An assistive listening device such as an FM system, improves the acoustic environment and makes speech more accessible to the deaf/hard of hearing individual. An FM system is similar to an FM radio, with a speaker "broadcasting" his or her speech to a listener's FM receiver. The speaker wears a lapel microphone and transmitter with the microphone located near the speakers mouth (which is the key to the benefits provided by an FM system). The person receiving the signal wears a receiver.

How FM Systems can Help

Everyone, regardless of hearing loss, hears close sounds better than distant ones. This is because all sound rapidly loses strength traveling even short distances. Background noise only makes matters worse. Because the sound signal is already greatly weakened after even slight distances, it does not take much noise to cover up or "mask" the desired signal. In addition, noise, distance, and echo make understanding sounds fatiguing at best and impossible at worst.

Hearing aids lack the ability to discriminate and filter out background or "white" noise and amplify all sounds equally. As a result, the deaf/hard of hearing person usually experiences greatest difficulty in group situations or when background noise is present.

FM systems overcome these problems by improving the "signal-to-noise" ratio. When the speaker talks into the transmitter, it is received by the listener's receiver just as if the speaker was standing right next to the listener's ear. As a result, the signal remains strong and stable. Further, an element in the transmitter rejects background noise while focusing on the desired speaker. This further enhances the strength and clarity of the signal received by the listener. The result is improvement in sound accessibility that can be quite pronounced.

Basic Operation

The transmitter and receiver work together as a system to strengthen and stabilize the speaker's voice while reducing the effects of unwanted background noise. For the speaker's FM signal to be heard, transmitter and receiver switches must both be turned on.