Listening devices

Hearing aids amplify sound but they so not provide perfect hearing. A hearing aid may be helpful in the ear with the hearing loss.

Hearing aids today are digital. The microphone picks up the sound waves, which are converted into digits in the hearing aid. The audiologist uses sophisticated software to manipulate the digital signal to:

• set a specific amount of amplification at each frequency to suit the user
• control feedback
• reduce the harsh effects of loud noises and
• suppress background noises.

In Australia, children with a permanent hearing loss who use a hearing aid receive free audiological care through Australian Hearing which is funded by the Australian Government. Children who do not have hearing aids will be reviewed at key stages (at approximately 10 months of age, 4 years of age and before starting school).

The decision to provide a child with UHL with a hearing aid is not as clear-cut as most parents would like. Research is being carried out around the world on the best way to manage UHL, but there are still no recommended guidelines on best practice.

In recent years, we have learnt a lot about the development of the human brain and there is compelling evidence about the importance of building good neurological pathways in the early months and years.

There is also compelling evidence that most babies with a bilateral hearing loss (hearing loss in both ears) who are diagnosed early and provided with hearing aids and good early intervention will develop age-appropriate language skills by the time they start school. It seems logical that doing the same for babies with UHL would be the best for the development of their neurological pathway in their affected ear, but we do not know if this is in fact the case.

Some audiologists remain concerned about fitting a hearing aid in a child with a hearing loss in one ear because of a phenomenon called binaural interference. The consequence of binaural interference may be that hearing with both ears is poorer than hearing with one ear. There has been little research done on binaural interference in children. However, might a child have better listening ability with one hearing ear and no amplification in the other ear? We do not know the answer to this question either. ¹³

Because we don't have any clear evidence to guide the management of unilateral hearing loss, the decision to aid or not to aid is made on a child-by-child basis taking into consideration each child's listening needs and difficulties.¹⁴ Once all possible options have been considered, the decision is largely left to the parents. You don't need to make a decision immediately. The audiologist at Australian Hearing will provide you with information on possible technology solutions for your baby and guide and support you in whatever decision you make.

If you decide against a hearing aid now, you can always review the situation in the future. And vice versa: you may decide to trial a hearing aid but feel there are no noticeable advantages for your child, and discontinue its use.

• The more severe the UHL, the greater the impact it will have on your child's ability to listen, particularly in noisy environments.

• There is evidence that some children with UHL experience problems, particularly at school. Children who are at highest risk are:
• Children with severe-to-profound congenital unilateral sensorineural hearing loss (SNHL)
• Children with a hearing loss in their right ear
• Children from lower socio-economic backgrounds and
• Children with a unilateral SNHL and a history of middle ear infections¹⁵
• Children with a profound UHL are considered poor candidates for traditional hearing aids. The amplification of traditional hearing aids does not provide access to conversational speech in the ear with the profound loss, and the quality of sound provided by the hearing aid my interfere with the good quality of sound in the hearing ear.¹⁵

• If amplification provides the child with access to conversational speech, then, theoretically, a hearing aid should increase the probability that the child would maintain age-appropriate language, academic and socio-emotional development.¹⁵

• Different international studies have found that between 7% and 48% of children with UHL use amplification.15 We do not have any data for Australia.

• The older the child at the time of first fitting a hearing aid, the greater the risk the child will reject its use. Children fitted with a hearing aid when they are young, tend to be more compliant about wearing the aid.¹⁵

• A hearing aid will not cause any harm to your child's residual hearing. Hearing aid prescription is very specific for each child.

Types of hearing aids

Different types of hearing aids suit different hearing losses.

1. Behind-the-ear hearing aid (BTE)
   This aid fits behind the ear and is attached to an ear mould which sits in the ear canal and transmits sound from the hearing aid into the ear. This hearing aid will provide greatest benefit to children with a moderate to severe unilateral hearing loss. it is fully subsidised and available from Australian Hearing. These hearing aids can also be used with an FM system at school.


2. CROS (Contralateral Routing of Sound) hearing aids
   CROS ids have two parts and look like conventional hearing aids. A microphone in the hearing aid on the deaf side transmits sound to the hearing aid in the hearing ear. These aids are not popular because the device is in the hearing ear. CROS aids are fully subsidised and available through Australian Hearing.


3. Bone conduction hearing aid
   In certain circumstances, a child cannot wear or benefit from the use of a behind-the-ear hearing aid. This includes children with a profound hearing loss and those with microtia and atresia. Bone conduction hearing aids transmit sound through the bone of the skull directly to the cochlea, bypassing the outer and middle ear. Bone conduction is not as efficient as hearing through the air but it is a valuable alternative for children who cannot use a traditional hearing aid.

A few bone conduction hearing aid options are available in Australian but not all are available through Australian Hearing.

• Traditional bone conduction hearing aids (BCHA) are fully subsidised through Australian Hearing. the bone conduction hearing aid consists of a head band to which a hearing aid is attached on one side and a vibrator on the other. This vibrating part needs to fit firmly on the head to work effectively and this can be uncomfortable and is not always tolerated by young children. BCHA can also be placed into a soft headband or hat.
  
  
• Contact Mini is fully subsidised for children under 5 years through Australian Hearing. In children over 5 years, it is available as a 'top-up' aid. The Contact Mini is a digital miniature bone conduction hearing system which can be housed in a variety of headgear or headbands. It is suitable for a mild to moderate hearing loss. This hearing aid may be uncomfortable for young children.
  
  
• Baha ^® Softband is a relatively new option for children but it is expensive and not available free through Australian Hearing. The Baha^®Softband consists of an elastic headband, a sound processor and a connector disc which is held against the skull. Sound travels from the sound processor via the connector through the bone of the skull to the inner ear. A few families in our online group have chosen to buy a Baha^®Softband for their baby. They are tolerated by babies and young children and parents have been pleased with the results.
  
  
• Transear looks like a conventional hearing aid but is a bone conduction hearing aid for individuals with single sided deafness (profound unilateral hearing loss). Transear is not currently available in Australia.

How much do hearing aids cost?

The cost depends on the type of hearing aid or FM system and whether it is available through Australian Hearing or not.

• Some hearing aids and FM systems are fully government-subsidised and are provided at no cost to children under 21 years of age through Australian Hearing.
• Some hearing aids have more features or improved technology and, while they are available through Australian Hearing, you will need to contribute to the cost of the device. These hearing devices are know as 'top-up' devices or aids.
• Some hearing aids are not available through Australian Hearing and parents will need to organise their purchase independently. Technology is changing rapidly and the list of available aids through Australian Hearing does change so it is always worth checking with your audiologist at Australian hearing first.

What to expect from a hearing aid

The way a child responds to a hearing aid is quite varied. Many parents of babies with unilateral hearing loss are disappointed with the hearing aid as they don't feel they notice any difference in the baby's ability to hear with the hearing aid and they wonder whether they have made the right choice. In this case, it is worth remembering the rationale behind providing babies with hearing aids, i.e. to develop the auditory pathways and improve the prospect for normal language acquisition. Persistence may be rewarded in the long run.

The responses of older children are also varied. Children diagnosed with unilateral hearing loss when they are older are not always compliant with hearing aid use. Their brain may need time to adapt to the new sounds and you may need to show some patience and perseverance with them. Encourage them to use the hearing aid at home first, in a quiet environment, and build up the amount of time they wear the hearing aid. Wearing the hearing aid when watching television is often a good place to start.

Older children also tend to worry about the cosmetic appeal of the hearing aid. Your response to the hearing aid will impact on hoe your child feels about wearing it. If you fuss about hiding the hearing aid with their hair, or remove it for photos or special occasions, you may be giving them the message that the hearing aid is something they should hide and this can result in an unwillingness to wear it.

The most successful hearing aid users understand why they need a hearing aid and are able to tell other people about their hearing loss. Teach your child to confidently explain why they need a hearing aid. In time, the hearing aid will become part of who they are.

Children with unilateral hearing loss who do not use a hearing aid will be reviewed by Australian Hearing at around 10 months of age, around 4 years of age and again prior to starting high school. Functional tests can be undertaken to determine if the UHL is affecting the child's listening in everyday situations and whether any listening device may be of some benefit.

If you decide on a hearing aid for your baby, the two main challenges are:

• stopping it whistling
• keeping it on!

Ear moulds sit in the ear canal and transmit sound from the hearing aid into the ear canal. When ear moulds are loose, they cause the hearing aid to whistle which is uncomfortable for everybody. Babies' ear canals grow quickly and the ear moulds will need to be replaced frequently in the early months. This involves the audiologist taking an impression of the ear canal and sending this off the the ear mould manufacturers. Te ear mould will take a couple of weeks to be made and can be posted to you which is usually more convenient. The ear mould comes with longer tubing than is necessary and you will nee to carefully trim the tubing to the right length for your baby. Ask the audiologist to show you how to do this the first time. Rubbing some ear mould lubricant (available from Australian Hearing) around the mould may also stop the whistling. The lubricant creates a better seal and reduces the amount of feedback which causes the whistling.

The second challenge is keeping the hearing aid on as the baby grows. They tend to pull them out and this can be frustrating, particularly when you are not around to see where it has disappeared. Babies tend also to put the aids in their mouths. The hearing aids have small batteries and although the battery case door is tamper-proof, it is best to avoid the possibility of your baby accidentally swallowing a battery or an ear mould.

There are a couple of solutions here and the most popular one with mums appears to be using pilot caps on the baby for a time. Pilot caps are similar to the old aviator caps. They are made from soft fabric and fit snugly over the ears and tie under the chin. These make it more difficult for a young child to pull off the hearing aid. They can be purchased at a number of the early intervention services. A pattern for a pilot cap is on our website from Auditory Verbal UK which those handy with a sewing machine have found successful. The baby soon grows out of this phase and it is worth persisting if you have decided on using a hearing aid.

IMPLANTABLE DEVICES

These are devices that require surgery. The surgery and device may be refundable under some private health funds.

1. Baha^® Bone Conduction Implant
   The Baha^® is an implanted bone conduction device and consists of three parts:
   
   • a sound processor
   • a connecting abutment
   • a titanium implant placed in the bone behind the ear during surgery.
   Sound is picked up by the sound processor, which turns it into vibrations. These vibrations are transferred through the implant via the connecting abutment. The sound vibrations are then transferred through the bone of the skull directly to both cochleas bypassing the outer and middle ear.
   
   The Baha^® is suitable for people with
   
   • a conductive loss: outer or middle ear problems
   • a mixed hearing loss: outer and middle ear problem combined with an inner ear problem
   • Single-sided sensorineural deafness: total deafness in one ear
   Surgery is required to place the implant in the bone behind the ear and the implantable device is not suitable for babies and young children . The bone of the skull needs to be thick and strong before it can accomodate the implant.
   
   The Baha^® sound processor is fully subsidised by Australian Hearing for children over 5 years of age with bilateral atresia.
   
   
2. Vibrant Soundbridge^®
   The Vibrant Soundbridge^® (VSB) is a middle ear implant system suitable for conductive and mixed losses. This is a relatively new device in Australia and the manufacturers report good results in children with microtia and atresia as young as 3 years of age. The implanted device sits under the skin and can be implanted in young children. The VSB only delivers sound to the cochlea on the side of the hearing loss and therefore does not affect the quality of sound in the hearing ear.
   
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FM SYSTEMS

Personal FM systems help to eliminate the difficulties caused by background noise, distance and acoustics and are particularly helpful in the classroom. This is the most effective listening device for children with UHL in the classroom. An FM system provides the best available access to the teacher's voice.

The FM system consists of a transmitter and a receiver. In the classroom situation, the teacher wears a small lapel microphone which is attached to the transmitter. The transmitter sends the sound via FM transmission to the receiver, which is usually attcehd to the hearing aid.

If a child does not wear a hearing aid, there are three possibilities:

• Oticon Amigo FM system is fully subsidised and available through Australian Hearing. The Amigo system consists of a body-worn transmitter and receiver. The receiver is coupled to headphones or earbuds, which the child wears.
• iSense Classic is an FM receiver designed for people who do not wear hearing aids. It looks like an MP3 player with a thin cable bringing the signal to earbuds in the ears.
• iSense Micro is a Bluetooth headset which sis behind the ear. iSense products are available as 'top-ups' from Australian Hearing.

WHOLE ROOM SYSTEMS

Soundfield Ampilification Systems

This is an option for children when they start school. A large part of the school day is spent listening. Children listen differently to adults. They lack the expereince and knowledge to interpret what is being said in a noisy environment. Children need a quieter environment and a louder signal-to-noise ratio than adults in order to learn. The better a child can hear, the more he will learn.

The goal of soundfield amplification is for every child in the classroom to hear the teacher's voice, no matter where they are sitting and where the teacher is facing. Soundfield amplification systems overcome adverse classroom conditions, such as poor acoustics anf high ambient noise levels and make it easier for all children to hear the teacher. The advantage of a soundfirled system is that individual children are not singled out as requiring assistance.

Several soundfield systems are available using different technologies. However, all increase the signal-to-noise ratio in the classroom and consist of a transmitter microphone, receiver/amplifier and speakers. The systems with four speakers mounted around the classroom will provide the best quality sound. There are also portable devices, which are less costly, and parents and treachers report good results.

Funding for soundfield systems

There are a variety of options for funding of soundfield systems:

• The school may fund the soundfield system for the classroom - discuss this option with the school principal.
• Some parents have chosen to purchase a portable system for their child's classroom.
• Lions Hearing Dogs supply a limited number of soundfield systems to primary schools each year. The application form is available at http://www.hearingdogs.asn.au/about-us/school-sounds-systems/