How do Hearing Aids Work?
Hearing loss is on the rise in Australia. Presently, one in six Australians are affected by hearing loss, and this number is predicted to increase to one in four by the year 2050.
Although there are a range of factors for this steep incline of people living with a hearing issue, the main reasons are ageing and repeated exposure to loud sounds. Modern day living is noisy. Add that to the fact that young people are subjecting their ears to excessively loud music, and it’s no surprise that hearing loss is becoming more prevalent.
It’s hard to appreciate just how vital our hearing is as it is so well integrated into our daily life. We rely on it to work, socialise, communicate, relax, and unwind. It can alert us to potentially dangerous situations and help us to keep ourselves safe. So, when it starts to deteriorate, it can be confusing, lonely and even a little bit scary.
Left untreated, hearing loss can cut people off from those around them and lead to social isolation and feelings of depression. Although a hearing aid can never wholly restore hearing, it should significantly ease communication problems, improving quality of life for the wearer and those around them.
Thankfully, hearing aids have come a long way in the last few years. Modern devices are significantly smaller and more efficient than their older counterparts. In saying this, the concept behind their functionality – amplification – has not changed. Amplification is still considered the most effective way to treat most forms of hearing loss.
Choosing the right hearing aid is something that should be discussed with a professional audiologist. Click here to book a free hearing test now.
Types of Hearing Loss
There are different types of hearing aids for different types of hearing loss.
Sensorineural hearing loss – this is usually caused by damage to the hair cells that line your inner ear, or to the nerve pathways that lead from the inner ear to the brain. The two biggest causes are excessive exposure to loud noise and age. It is the most common type of hearing loss and is typically treated by air conduction hearing aids.
Conductive hearing loss – this affects the passage of sound between the eardrum and the inner ear. It is caused by some kind of physical interference that prevents the proper transmission of sound waves. This could be an obstruction or damage, and may only be temporary and treated with medication. If it is permanent, bone conduction hearing aids may help.
Unilateral hearing loss – total hearing loss on one side but normal hearing or a mild hearing loss on the other. This is also called single-sided deafness and can be treated with a bone conduction hearing aid on the non-hearing side.
Types of Hearing Aids
Hearing aids can differ by:
- Design: Shape, size, colour, the position they are worn in the ear.
- The technology used: Whether the hearing aid uses analog or digital technology to achieve amplification. Whether it is air conduction or bone conduction technology.
- Special features: Availability of extra benefits, like Bluetooth connectivity.
Air Conduction Hearing Aids
Analog: The Simple Version
In their most simple form, hearing aids have three essential components. No matter what style or size, they all have a microphone, amplifier, loudspeaker (also know as a ‘receiver’), and power supply. But how exactly does an analog hearing aid work?
The process works as follows:
- The microphone receives the sound and converts it into an electric signal.
- The amplifier, which is located between the microphone and loudspeaker, strengthens or boosts the electric signal which increases the amplitude of the sounds supplied by the microphone.
- The loudspeaker then converts the electric signal back into sound which flows through the tube, ear mould and into the wearer’s ear.
Esentially analog hearing aids convert all sounds received into electric signals, boost those signals, and turn them into louder sounds. They tend to amplify everything by the same amount.
So if someone is speaking to you, their voice and all the background noise around you will be amplified. An analog hearing aid can be configured, to a certain degree, to boost the frequencies that you struggle to hear, while leaving audible frequencies without hearing impairment unaffected. Your audiologist will consult your audiogram to find out the exact pattern of frequencies you can and can’t hear and adjust the aid accordingly.
Programmable Analog Hearing Aids
Programmable analog hearing aids are also available. They have a variety of settings that you can choose from to give you different levels of amplification in all kinds of everyday environments.
When the device is manufactured, the settings will be preset according to the exact pattern of frequencies you can and can’t hear, and you can flick between these settings using a small switch on the device when needed.
While these are more sophisticated than the standard analog aids, they will still amplify all sounds, including background noise.
Digital: A Little More Complex
These aids have a computer chip that intelligently analyses the sounds that are received by the microphone. They can convert the sound wave into digital signals rather than electric signals, and this allows the aid to process the sounds more complexly, figuring out which sounds you want to be amplified and which ones you don’t. It does this by using DSP (digital signal processing).
DSP can make a difference in many ways, including:
- Improved Speech Understanding – Digital aids can intelligently amplify speech with the use of directional microphones. These are designed to pick up speech more when the source is in front of the user while ignoring sounds coming from the sides and back of the user i.e. background noise.
- Gain adjustment – Gain is how much an amplifier increases a particular frequency. Digital hearing aids can automatically adjust the gain for around a dozen frequencies according to the wearers’ hearing loss.
- Sound classification – This determines the types of sounds being detected e.g. music, speech, traffic etc. It selectively amplifies or reduces sounds, picking up information about the environment you’re in, and applying a specific amplification setting based on that knowledge. So, if someone has trouble hearing higher frequencies like children’s or women’s voices, the aid will automatically adjust to boost these frequencies. Analog aids can also do this to a lesser extent, usually by the wearer switching settings.
- Less Feedback – Feedback managers are now a staple in digital hearing aids to reduce that high-pitched whistling sound significantly.
Digital aids are not superior to analog aids because they are better at amplifying sounds. Rather, the sounds received can be processed in a much more intelligent way.
The information produced by the digital hearing aid allows for clearer speech, reduced traffic noise, and a more pleasant experience when listening to music – all of which occurs during the amplification process.
Amplification only helps hearing loss if the inner ear, also known as the ‘organ of hearing’, or the cochlea, is damaged (but not too severely). All the other pathways have to be clear and working well in order for the sounds to be cleanly transmitted all the way to the inner ear.
If there is a problem with the passage to the inner ear but the inner ear is working fine, bone conduction aids may help.
Bone Conduction Hearing Aids
Bone conduction hearing aids create vibrations that are sent across the skull to the inner ear, directly stimulating the cochlea where these vibrations are perceived as sound. So if there is an issue with the outer and middle ear components, the process of transmitting sound by air can be bypassed.
An audio processor is used to pick up the sounds and convert them into mechanical vibrations which are then passed through the skull. The audio processor is either kept in place by a headband, or a surgically implanted abutment or magnet underneath the skin.
The inner ear processes the mechanical vibrations in a similar way to natural hearing and transmits this acoustic information to the brain. It can take some time for the brain to get accustomed to receiving this new type of information and recognising it as sound. It is recommended to work with a professional to make the initial period of adjustment as comfortable as possible.
Over 90% of individuals with a hearing loss will require the use of traditional hearing aids as their best and only treatment option. The remaining 10% may not receive benefit from this aid. For individuals with a conductive hearing loss, mixed hearing loss or single-sided deafness, a bone conduction device may be helpful.
The ever advancing technology in hearing aids enables you to stay connected to the world around you. The first step is meeting with an audiologist who can assist you by testing your level and type of hearing loss and providing a diagnosis.
Click here to book a free hearing test now.