Hearing aid technology

There are three types of hearing aid technology.

• Analog hearing aids
• Digitally programmable hearing aids
• Digital hearing aids
• Which hearing aid is best for your child?
  

Analog hearing aids

With an analog hearing aid the electronic adjustments that need to be made so that each client can hear well can only be done manually by the audiologist using a small screwdriver to turn tiny internal controls called trimpots (potentiometers).

Sounds of different strengths are represented inside the analog aid by voltages of different sizes. Electronic components are used to modify the voltages to:

• Make the sounds louder (amplifying)
• Make some sounds louder than others (filtering)
• Keep the sounds at a comfortable level (compression and limiting).
  

Prior to 1991, all Australian Hearing hearing aids were of this analog type.

Digitally programmable hearing aids

These hearing aids have two parts – a programmable memory and an analog amplifier.

The audiologist programs the hearing aid’s memory using a computer, and the memory then tells the analog part of the hearing aid what to do.

The great advantage of digital-analog hearing aids also have the potential for more than one listening program. For example, different settings can be used in different listening conditions, such as in quiet (e.g. a library) and in noise (e.g. a playground). The programmable memory of these hearing aids provides the potential for more than one listening program. Some of the hearing aids fitted by Australian Hearing are digitally programmable.

Digital hearing aids

These hearing aids have become available in the last few years and have the potential for even greater flexibility than previous technologies.

In fully digital hearing aids the sound is converted by a digital converter into a series of numbers. The processor then performs arithmetic on these numbers to change the sounds before turning them back into an analog signal.

Digital hearing aids are sometimes referred to as having “CD sound quality” as they use the same technology as compact disc players. However, by the time the hearing aids get to manipulate the sound, the background noise has already been mixed in. CDs on the other hand are usually made in very quiet sound recording studios under ideal conditions. The result is that CDs have no background noise, and this is unlikely to ever be true for hearing aids which have to operate in real life situations.

Many digital hearing aids amplify sounds in a “non-linear” fashion. This means that they amplify soft sounds more; medium sounds similarly to any other hearing aid; and loud sounds less. This makes listening more comfortable, especially in noise.

Some digital hearing aids have particular features to try to suppress background noise or to use directional microphones to help with reducing background noise. Some also have sophisticated feedback (whistling) management circuits. In future, digital hearing aids will be built that have few restrictions on what they can do to modify sounds for the hearing aid user.

Most of the hearing aids fitted by Australian Hearing are fully digital.

Which hearing aid is best for your child?

A number of factors come into play when determining which hearing aid will best suit your child’s needs.

1. The degree and type of hearing loss
   The range of hearing aid styles that would suit your child may depend upon the type and degree of hearing loss.
2. Speech Discrimination
   How clearly can they hear speech? If sound traveling from the ear to the brain is distorted, as it can be with some types of hearing loss, the benefits of the advanced technology features may be more limited.
3. Developmental level
   Children have different hearing and listening needs at different stages of their development.
4. Independence with hearing aid management
   Some hearing aid features need to be switched on or off by the listener, depending upon the listening conditions. Age is a factor when considering these features.
5. Activities
   What sort of activities does your child do in a typical week? Where do they have the most hearing difficulty? This information will help you to select which of a wide range of hearing aid features may be useful for your child.
6. How your child feels about wearing hearing aids
   It is also important to consider how the child feels about wearing and managing the hearing aids.
   

Australian Hearing offers children a range of high quality, fully digital hearing aids, some which are fully subsidised (ie. no cost to the families) and some which are partially subsidised.

The features in the fully subsidised range are those which research suggests will suit the hearing and communication needs of most children with hearing loss.

The hearing aid models which offer special features and advanced technology are also subsidised and the family covers the additional cost.

Different hearing aid manufacturers may use a range of terms to describe the features of their particular hearing aids. Your audiologist will be happy to answer any questions you have about particular hearing aid features and how they may or may not be helpful for your child.

Modern hearing aids have many features to enhance the speech signal as it enters the ear. However, the final sound that the listener hears is influenced by the amount of damage in their auditory system. For instance, if a child has profound hearing loss and their cochlea is not detecting or transmitting the full range of speech sounds to the brain, even the most sophisticated hearing aid cannot restore perfect clarity.

Information provided by Australian Hearing




Reproduced with permission.
Date reviewed: 25.11.2008