assistive listening device on:
[Wikipedia]
[Google]
[Amazon]
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.
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 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.
Usage
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 throughpublic 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 ...
or 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 sou ...
systems, such as in places of worship or lectures.
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).
Technology
The assistive listening device usually uses amicrophone
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 publi ...
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 (''telecommunication'') between two or more points without the use of an electrical conductor, optical fiber or other continuous guided transm ...
ly through means of frequency modulation
Frequency modulation (FM) is a signal modulation technique used in electronic communication, originally for transmitting messages with a radio wave. In frequency modulation a carrier wave is varied in its instantaneous frequency in proporti ...
(FM), infrared
Infrared (IR; sometimes called infrared light) is electromagnetic radiation (EMR) with wavelengths longer than that of visible light but shorter than microwaves. The infrared spectral band begins with the waves that are just longer than those ...
(IR), an audio induction loop
An audio induction loop system (also called an audio-frequency induction loop or AFIL, or a hearing loop) is an assistive listening device for individuals with reduced ranges of hearing.
History
The first patented magnetic induction loop co ...
, 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.
See also
References
{{Reflist Assistive technology