The Technology of Hearing aids:
Analog vs. Digital
Technology Types:
Hearing aids are are built from analog or digital circuits. Each technology processes sound differently. Until recently, all hearing aids were analog. Digital hearing aids are the newest kind of hearing aid and are superior to analog.
Analog vs. Digital:
All hearing aids, whether analog or digital, are designed to increase the loudness of sounds reaching the ear drum so that the hearing-impaired person can better understand speech. To accomplish this, hearing aids require three basic components:
1. A microphone to gather acoustic energy (sound waves in the air) and convert it to electrical energy.
2. An amplifier to increase the strength of the electrical energy.
3. A receiver, which is like a miniature speaker, that converts the electrical energy back into acoustic energy (sound waves). What makes digital hearing aids different from analog hearing aids is what happens in between.
Technology Types:
Each technology processes sound differently. Until recently, all hearing aids were analog. Digital hearing aids are the newest kind of hearing aid and are superior to analog.
Analog Hearing Aids:
Photo courtesy Unitron Hearing
Analog hearing aids use a continuously varying electrical signal to produce sound, just like a microphone and loudspeaker. Analog hearing aids have a microphone that picks up sound and converts the sound into small electrical signals. These signals vary according to the pattern of the sound. The signals are then amplified (made louder) by transistors and fed to the ear phone on the hearing aid which is next to your ear drum so you can hear them. Most of the better analog hearing aids compress the sound using 'automatic gain control" (AGC). This amplifies quiet sounds until they are loud enough to be heard, but gives less amplification to sounds that are already loud, so you're protected against uncomfortably loud sound levels. Analog hearing aids don’t have all the features that come with advanced digital aids, but they are the least expensive hearing aids available.
Digital Hearing Aids:
Photo courtesy Unitron Hearing
Digital aids work in a different way than analog.
Digital hearing aids take the signal from the microphone and convert it into "bits" of data
("1"s and "0"s) - numbers that can be manipulated by a tiny computer in the hearing aid. This makes it possible to tailor and process sounds very precisely, in ways that are impossible with analog aids. The bits representing the sound are analyzed and manipulated by algorithms (a set of instructions) to perform precise, complex actions, and are then converted back into electricity, which is finally changed back into sound that goes into the ear. This process happens very rapidly: there are several million calculations occurring in the hearing aid per second. The numbers can be manipulated in almost any way imaginable, and this is what gives the digital hearing aid its big advantage. The binary numbers can perform numerous complex calculations that create very precise, very flexible hearing aids.
Cutting out background noise
When someone talks to you, you usually want to hear what they are saying, rather than whatever noise is going on in the background. People who use traditional analog hearing aids often complain that they find it difficult or impossible to follow conversations in noisy places.
Many digital aids are designed to reduce steady kinds of background noise, such as the rumble of traffic or the whirr of a fan. This makes listening more comfortable. But it does not necessarily help you to pick out a single voice from everything else that's going on, especially when several people are talking.
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