How Hearing Aids Work

Hearing aids have come along way since their initial invention in the 17th century; today we enjoy the clarity and automation of digital hearing aids, which can be selected and fine tuned to meet almost anyone's needs.

These devices, which are now more akin to miniature computers now than amplifiers, transform sound in a number of stages. In this article we'll examine how hearing aids work and look at the different styles available.

1. Microphones

Most hearing aids will have two microphones concealed in the body somewhere behind tiny holes or slits. One faces forward and one backward, giving a 360-degree capture capability. These microphones are highly sensitive and can be manipulated by the hearing aid in real time, such that if background noise is detected behind the listener, sophisticated devices will attenuate or switch off the rear facing microphone, cleaning the signal for the listener automatically. This 'directionality' greatly enhances the clarity of speech in noisy environments and is one of the most widely used features in modern hearing aids today. Once sound is picked up by the microphones, it is transformed into digital signal that a computer can understand and is sent to the processor.

2. Processing

As mentioned before, hearing aids are more like computers now than they are amplifiers. Even more so because digital aids have a computer processor inside of them, capable of handling millions of calculations per second, fast enough to ensure the wearer of the hearing aid does not notice any lag or delay in sound.

The processor is where the 'magic' happens, and allows the sound you hear to be manipulated in a number of ways, such that it is delivered to the ear in the cleanest, most natural way possible. Like a mixing desk in a music studio, the processor allows the aid to perform a number of functions, including:

making sounds clearer by boosting certain pitches and cutting others
deciding whether or not to make the aid's microphones directional
allowing more sophisticated aids to connect to mobile phones
automatically adjusting the volume for the listener to maximise speech understanding
quickly limiting loud sounds that occur to protect the wearer's ear from over amplification

All of these features can be controlled by the Audiologist during a hearing aid fitting appointment, meaning high quality digital hearing aids are highly customisable and can be tailored to an individual's specific needs.

3. Sound outlet

Once the sound has been processed it can be delivered to the ear through a very small but extremely powerful, high quality speaker. The design of these units is a marvel of engineering, considering how loud they can be made without distorting or breaking, and all whilst being manufactured in a size smaller than a pea. The exact dimensions of the speaker (or receiver unit) is slightly different depending on the manufacturer and selection of the Audiologist. They can be ordered in a range of different sizes to suit the requirements of each individual, from very small and modestly powered units for mild losses, all the way up to larger more robust units for profound hearing loss.

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