How Hearing Aids Work - An Audio Door to the World
Hearing aids give a wonderful assistance to the partially hearing today, allowing their lives to be both fuller and richer. Thus enabling these people to play an active part in many aspects of the modern world that they would otherwise be excluded from.But just how do they work? What goes on in your ear?
Let us start our tour of this important subject by looking at the human ear itself.
Sound travels through the air in waveforms, and these are gathered in by the ear and altered, before being sent to our brains to be interpreted. That is their purpose in life, so now let’s see how the ears achieve their goal.
For this, the ear is divided up into three different parts; the outer ear, the middle ear, and the inner ear.
The sound waves enter through the outer ear (correctly called the auricle or pinna) which is so shaped that the sound is directed into and through the ear canal towards the middle ear and the eardrum, which they hit. This eardrum, which is really a tight membrane, vibrates like a real drum when struck and the vibrations now caused are transmitted to a group of three minute bones collectively called the ossicles and individually known as the malleus, the incus, and the stapes. Or alternatively, you may come across them being referred to as the hammer, anvil and stirrup. These three bones are also the smallest to be found anywhere in our bodies.
The ossicles work as a team to collect the traveling vibrations and send them onto the inner ear and the waiting cochlea. This organ looks like a snail’s shell and contains a series of tubes that are liquid filled and also home to tiny hairs. When the vibrations arrive here, they cause a rippling effect in the liquid which bends and otherwise moves the hairs. This in turn creates electrical impulses that race along the connected auditory nerve and on into the brain for processing and identification.
Quite an intricate procedure then, and unfortunately, sometimes things do go wrong.
In the United States it is estimated by some authorities that near to 10% of the population suffer from some type of hearing difficulties at any one time. These ailments do not depend on gender, race, age or financial income to exist. Though senior citizens do suffer various conditions more, around 31%-32% of this group suffers as opposed to 1%-2% of American children.
These stats do not mean total deafness of course, problems with hearing can range widely from the slight and irritating right through to the extremely distressing. As well as differing levels of trouble there are distinct causes that are encountered by doctors.
Congenital hearing loss means suffering ear problems right away from birth. It may be caused by disease or illness during pregnancy, extended birth complications or an inherited condition.
Conductive hearing loss, which can be both temporary and permanent, is due to the prevention of sound reaching the inner ear. The trouble therefore lies in the outer or middle ear. The most common cause of congenital hearing loss is a build up of too much earwax. Other than this, the culprit might be an infection, fluid trapped in the middle ear, damage to the ossicles, or either an inflammation or a puncture of the eardrum. These situations can usually be cleared up by medical procedure.
Nerve hearing loss (Sensorineural) is a permanent situation where the auditory nerve itself or the miniscule hair cells inside the cochlea are damaged. The root of this could lie in aging, illness, infection again, head injury, exposure to excessive noise, the side effects of a medicine, or genetics.
Mixed hearing loss is conductive and sensorineural together in some form of combination.
The modern solutions
As scary as some of that may sound, luckily hearing aids are here to help!
Hearing aids may come from many diverse manufacturers but the basics are the same, regardless of size or styling.
They are electronic devices for amplifying sound with four central components: a battery, circuit, microphone and receiver. Most now also have some form of internal or external controllers.
The microphone or microphones (some hearing aids have two, for differing degrees of amplification) receives the incoming sound from any source and changes or converts it into varying electrical impulses (for analog). These then are sent to the circuit which is responsible for the amplification of the current according to its prescribed settings. These settings are very important, because different users will have different requirements from their aid, depending on their individual disability, and the sound environment that they are in. Next, the correctly amplified electric current is taken to the receiver, where it is turned back into sound again (acoustic energy) and presented to the ear. The battery is of course there to provide the power for the system to work, with modern batteries being very long lasting.
Now for a closer inspection of the circuit. There are three types around nowadays; adjustable analog, programmable analog, and programmable digital. These sorts increase in complexity and therefore correspondingly in price.
The adjustable analog will have its settings decided on by the audiologist according to patient needs (these depend on what their ears can still hear by themselves, and what range of frequencies they need assistance with, and by how much) and then be built to specification, with room left for slight adjustment or fine tuning later. Volume control may be automatic or manual.
Programmable analog hearing aids are the next notch up. Here the audiologist programs it by using a computer. This allows for much more flexibility for the user, because the hearing aid can contain multiple settings, ready for different situations encountered in the outside world, and these can often be chosen by the user via a remote control. The fine tuners or ‘potentiometers’ as they are often called are now within the circuit rather than externally on the aid. Remember that a crowded restaurant or store is a very different place than inside a car or at a rock concert for example when trying to hear others speak. The frequencies and volume of background noise were the cause of much trouble in early hearing aids, which simply took everything in at the same level. Volume controls were present, but little in assisting with recognizing speech, and certainly not in the subtle changes of frequency within speech patterns themselves. This has now thankfully changed for the better, with adjustable and programmable hearing aids able to reduce the unwanted noises and augment the required as necessary.
The most expensive of these are the digitals, which feature DSP, or Digital Signal Processing. They have a computer chip inside which is capable of far more complex and accurate differentiating of sounds picked up by the microphone. It converts the sound waves into data, many millions and billions of number codes rather than electricity, and can therefore recognize and assign the proper settings of volume and frequency adjustment with amazing accuracy, leading to much clearer sounds (and the correct sounds) being heard by the users.
That’s the type, now what about the style?
First it must be decided if one or two hearing aids are required. If general hearing loss because of noise or age is the case, then a binaural arrangement might be preferable (one hearing aid on each ear). This can help with identifying the direction of the sound source, and also with recognition.
For those with sensorineural hearing loss the basic options are four in number.
Behind-the-ear or BTE hearing aids are worn unsurprisingly behind the ear, and linked to a plastic mold that fits in the auricle (outer ear). These are good for both adults and children suffering from any amount or degree of hearing loss. The molds must however be properly fitting to avoid a high pitched whistle or squeal known as feedback. For this reason they may need to be remade occasionally for the growing ears of children.
For this reason In-the-ear or ITE hearing aids are not recommended for children because they are worn entirely within the outer ear and the hard casing would need to be more regularly replaced due to growth. These hearing aids are for mild to severe hearing loss and can contain a telecoil, which is an internal extra device for assisting the hearing aids’ performance when used in conjunction with a telephone. They can also cause feedback because they are smaller and so the microphone and receiver are in closer proximity. These hearing aids can be damaged by earwax.
Canal hearing aids may be ITC, in-the-canal or CIC, completely-in-canal. These are custom built for the patients’ ear canal. Suitable for moderate to acute hearing problems, their extreme small size may be of a bonus to some for cosmetic reasons. But this can cause problems in adjustment and removal. They can be damaged by earwax and discharges and again are not suggested to be used by children.
Body hearing aids are only nowadays for those with the very worst hearing loss which is known as profound. Attached to a pocket or belt, the aid can be of the larger size required for the extra power. It is attached to an earpiece by a wire.
For those who cannot wear any of these because of a continually draining or malformed outer ear or ear canal and suffering from conductive or mixed hearing loss, a special kind of hearing aid known with a bone-conduction receiver may be worn with a headband. This sends sound waves through the side of the skull behind the ear and is completely safe but may lead to soreness and headaches because of pressure from the transducer on the skin.
If this is a concern then BAHA or bone anchored hearing aids should be considered .Here a sound processor is secured to the bone behind the ear by a small titanium screw or fixing, which may sound alarming but is routine surgery. This can then be covered by longer hair, and again uses the ‘bone road’ for transmitting sound directly to the inner ear.
The implant debate
Hearing implants that use micro-magnets positioned in the middle ear behind the eardrum combined with a device in the ear canal are a new and exciting possibility that have many saying that this is the way forward for hearing aids, offering perhaps even better clarity than the most advanced of digital hearing aids.
These are not controversial.
But cochlear implants for children certainly are, for health and cultural reasons. These electrical devices that attach to the auditory nerve allow for a different kind of hearing from experienced by healthy ears or other hearing aids, and that is beyond the span of this article.
Do you need a hearing aid?
If you suffer from any of the following you may well do:
- A more or less continual ringing or hissing in the ears. (Known as Tinnitus)
- Problems with hearing the television or radio at its regular volume level.
- Trouble hearing those talking to you, particularly when there is other noise present.
- Tiredness caused by increased efforts to hear sounds.
- Balancing problems or dizziness.
If you experience any of the above problems, consult an audiologist immediately, who will help you with tests and good advice on your requirements if it is established that the use of a hearing aid is advised.
And don’t be scared if this is the case, health problems are best dealt with rather than being ignored. ‘Letting things get better on their own’ is not usually the wisest of options. Many hearing aids today are not too expensive, and they are very small and discreet as you have learnt. Besides, most people you meet will not be as conscious of it’s presence as you are, and if, for children, their friends make fun of them; then those were probably not friends worth having anyway.
To finish, here are some helpful suggestions of questions that you should ask before making a purchase:
- Are there medical ways in which my hearing could be improved?
- Can I test my hearing aid before agreeing to buy?
- Which type is best for me?
- How long does the manufacturers warranty last?
- How long will repairs take if it does go wrong?
- Will I be allowed to use another aid for free if mine is being serviced?
- Am I being given full instructions?
- Is the hearing aid difficult to become familiar with?
- If yes to the last, then what troubles might I face?
These are just some questions that you may have, and the audiologist should be happy to deal with them for you. If not, go somewhere else!
You’re hearing is precious, and the world a finer place with its sounds accessible to you. The beauty of music and birdsong, the roaring of waves onto the shore, the happy laughter of loved ones. Don’t deny yourself these pleasures, hearing aids do not make you different, but they can make you happy!
About The Author
Matt Jacks is a successful freelance writer providing valuable tips and advice for consumers purchasing discount hearing aids, dr atkins diet menu plan, and mosquito control. His numerous articles offer moneysaving tips and valuable insight on typically confusing topics.
This article on "How Hearing Aids Works" reprinted with permission.
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