An assistive listening device (ALD) is part of a system used to improve hearing ability for people in a variety of situations where they are unable to distinguish speech in noisy environments. Often, in a noisy or crowded room it is almost impossible for an individual who is hard of hearing to distinguish one voice among many. This is often exacerbated by the effect of room acoustics on the quality of perceived speech.

Hearing aid A hearing aid is a device designed to improve hearing by making sound audible to a person with hearing loss. Hearing aids are classified as medical devices in most countries, and regulated by the respective regulations. Small audio amplifiers s ...

s are able to amplify and process these sounds, and improve the speech to noise ratio. However, if the sound is too distorted by the time it reaches the listener, even the best hearing aids will struggle to unscramble the signal. Assistive listening devices offer a more adaptive alternative to hearing aids, but can be more complex and cumbersome. A common usage is to aid people who are hard of hearing (HOH) by amplification and providing a better signal to noise ratio (SNR). The ALD may be used to help HOH people hear televisions and other audio devices, or to help people hear speech through

public address A public address system (or PA system) is an electronic system comprising microphones, amplifiers, loudspeakers, and related equipment. It increases the apparent volume (loudness) of a human voice, musical instrument, or other acoustic sound sou ...

sound reinforcement A sound reinforcement system is the combination of microphones, signal processors, amplifiers, and loudspeakers in enclosures all controlled by a mixing console that makes live or pre-recorded sounds louder and may also distribute those sounds ...

systems, such as in places of worship or lectures. The assistive listening device usually uses a

microphone A microphone, colloquially called a mic or mike (), is a transducer that converts sound into an electrical signal. Microphones are used in many applications such as telephones, hearing aids, public address systems for concert halls and publ ...

to capture an audio source near its origin and broadcast it

wireless Wireless communication (or just wireless, when the context allows) is the transfer of information between two or more points without the use of an electrical conductor, optical fiber or other continuous guided medium for the transfer. The most ...

ly through means of

frequency modulation Frequency modulation (FM) is the encoding of information in a carrier wave by varying the instantaneous frequency of the wave. The technology is used in telecommunications, radio broadcasting, signal processing, and computing. In analog ...

(FM),

infrared Infrared (IR), sometimes called infrared light, is electromagnetic radiation (EMR) with wavelengths longer than those of Light, visible light. It is therefore invisible to the human eye. IR is generally understood to encompass wavelengths from ...

(IR), an audio induction loop, or another method. The person who is listening may use a wireless Receiver to tune into the signal and listen at their preferred volume. There are also other consumer ALDs such as alarm clocks with bed shakers, amplified stethoscopes, baby monitors, and flashing door bell indicators. Most FM assistive listening devices operate on seventeen channels between 72.1000 and 75.800 MHz. The use of a wireless microphone placed next to the person speaking eliminates the sounds between them and listener, which reduces the effects of reverberation from poor room acoustics, background noise around the listener, and background noise around the speaker (by using a directional microphone). Font Awesome 5 solid assistive-listening-systems

Font Awesome 5 solid assistive-listening-systems

References

{{Reflist Assistive technology

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