Auditory SystemHearing ImpairmentAdults and EldersHearing AidsAuditory Health Care

Structure of Auditory System

Human auditory system consists of ears and auditory nerve connected to the cerebrum. An ear is made up of three parts, namely external ear, middle ear and inner ear.
The External Ear: the outer part of ear we usually see, including the pinna and the auditory canal; differentiated from the middle ear by the tympanic membrane.
The Middle Ear: an air-filled cavity in which three ossicles – malleus, incus and stapes – are housed as a channel for sound transmission between the tympanic membrane and the inner ear.
The Inner Ear: the fluid-filled cochlear which resembles a shell.

Principle of Sound Transmission
  1. The pinna collects sound waves which are transmitted along the auditory canal and strike the tympanic membrane.
  2. The tympanic membrane vibrates, resulting in the vibration of the three ossicles which are connected to it.
  3. The movements of the three ossicles set up waves in the fluid inside the cochlea; therefore the hair cells are stimulated and never impulses are generated.
  4. Nerve impulses are carried along auditory nerve fibres to the cerebrum for sound interpretation.

Hearing Impairment

Abnormality in or damage to any part of the auditory system may result in hearing impairment.

Degree of Hearing Loss

The intensity of sound is measured in Decibels (dB). Healthy auditory system is capable to detect sound equal to or lower than 25 dB, otherwise it is deemed as hearing loss. The degree of hearing loss is divided into 5 scales according to the decibel hearing level:

Degree Average Decibels Hearing Level (dBHL) Hearing Levels
Mild 26 —40 Difficult to sense weak sound
Moderate 41 —55 Barely able to cope with everyday conversation
Moderate to Severe 56 —70 Difficult in communication
Severe 71 —90 Only respond to loud sound
Depth ≥ 90 Difficult to sense sound
Types of Hearing Impairment

Hearing Impairment can be classified into 3 types according to the damaged parts:

1.Conductive Hearing Impairment

Despite normal functioning of the inner ear and auditory nerve, sound cannot be effectively transmitted into the inner ear due to dysfunction of external or middle ear, resulting in low volume.
Common Causes:

  • Otitis externa or otitis media
  • Trauma of the external ear
  • Blockage of the external auditory canal, e.g. wax blockage
  • Damage to the tympanic membrane
  • Ear bone hyperplasia
  • Congenital external or middle ear deformities, loss or insufficiency of functions

Resolutions:Temporary conductive hearing Impairment can be treated surgically or medically. Fitting hearing aids also facilitates sound amplification or transmission of sound into the inner ear via the skull.

2.Sensorineural Hearing Impairment

The most common type of hearing loss. Sound can be effectively transmitted through the external and middle ear but the inner ear due to dysfunction of or damage to auditory nerve, resulting to permanent hearing loss. Hearing impaired people of this type have reduced perception of sound intensity and tone quality, as well as deterioration in hearing and speech recognition.
Common Causes:

  • Ototoxic drugs
  • Degeneration of or damage to the nerve endings
  • Long-term noise exposure
  • Head injury
  • Tumors in the inner ear
  • Viral infections
  • Heredity

Resolutions: Generally hearing aids should be fitted but the corrective effect depends on the degree of impairment. In case of serious hearing loss, cochlear implant (CI) should be adopted to take over the original inner ear to stimulate the auditory nerve.

3.Mixed Hearing Impairment

The combination of conductive and sensorineural hearing impairments.
Resolutions: Hearing aids or cochlear implant (CI) should be employed, depending on contributing factors such as the degrees of the two kinds of hearing loss and the structure of ears.

Hearing Impairment in Adults and Elders
Interpersonal Relationship Hearing impaired people always encounter difficulties and misapprehension in social circumstances or telephone conversations, resulting in social withdrawal and isolation which bring harms to their interpersonal relationship.
Career Development Discussions during business meetings cannot be comprehensively understood and important messages may be missed or wrongly interpreted, affecting business decisions or progress, hence the work performance of the hearing impaired people.
Mental Health To avoid embarrassment in the course of communication, hearing impaired people may gradually isolate themselves from the others, giving rise to mental and social disorder, or even melancholia.

Dubious about whether you or your loved ones are suffering from hearing impairment? Pay more attention to the everyday particulars and you may have an idea of your hearing condition by answering the following questions:

  1. Is it difficult for you to hear high pitched sound (e.g. door bell, speech of women and children)?
  2. Do you have difficulty in following conversations in noisy environment (e.g. restaurants)?
  3. Do you often feel that people seem to mumble or speak unclearly?
  4. Do you often have to ask people to repeat what they have said before you understand the content?
  5. Do you need to lip-read so as to understand what people are saying?
  6. Are you often complained by your family about the high volume of TV or radio?
  7. Do you often experience difficulty in conversing over the phone?
  8. Do you often fail to respond to someone called from the back?
  9. Is it difficult for you to identify or locate the source of sound?
  10. Has anyone ever suggested that you might have hearing impairment?

The above-mentioned are in fact the common first symptoms of hearing loss. As the saying goes, “it is best to treat the disease early before it takes a hold”. Occurrences of 2 of the above circumstances suggest that hearing loss may be taking place. Please seek professional advice as soon as possible for early rehabilitation.

Ageing Hearing impairment in the elders is mostly caused by functional decline. Degeneration of hair cells inside the inner ear arises in adults between ages 30 to 40; however, it is difficult to be spotted as it takes place rather slowly. The World Health Organization (WHO) pointed out that over one-third of the elderly suffer from moderate or severe hearing loss.
Long-Term Noise Exposure Persistently working in noisy environment, such as construction sites and airports, increases the risk of occupational deafness. Listening to loud music also damage hearing.
Other Perforation of tympanic membrane, striking head or ears, viral infection and otitis media are the common causes of abrupt hearing loss in adults.

We hope that the provided information help you have a better understanding of your hearing status. Early diagnosis reduces the risk of aggravation of your hearing condition; therefore, if you are considering seeking professional hearing consultation and tests, act now!

Medical / Surgical Remedies Conductive hearing impairment usually can be treated by medical or surgical means. Those who encounter sudden hearing loss must immediately seek help from doctors or audiologists for timely rehabilitation.
Fitting Hearing Aids In case medical or surgical treatment is not applicable, fitting suitable hearing aids could be a way out. Most of the hearing impaired people can now enjoy desirable hearing experience with high-tech hearing aids and professional testing and fitting.
Applying Assistive Listening Devices Better hearing performance can be achieved by adopting assistive listening devices which can be used alone or along with hearing aids.

Hearing Aids

As the name suggest, a hearing aid is an assistive instrument for listening. Basically, it is a miniature amplifier which allows hearing impaired people to make good use of their remaining hearing capability and works as a complement to the defects of their auditory systems, so as to enhance their communication performances.


In 2015, there are 360 million people globally who have moderate or severe hearing loss, and 100 thousand in Hong Kong who suffer from deaf or hearing impairment, as revealed by WHO and Hong Kong Association of the Deaf respectively. The good news is, oversea research found that after fitting hearing aids, about 70% of the hearing impaired people realize noticeable improvement in interpersonal relationship, 90% experience higher living quality, and 40% becomes healthier. Therefore, taking an early step to look for resolutions could drive you to your ideal way of life!


A hearing aid generally consists of four main parts:

1. Microphone: To collect sound waves and convert them into electrical signals.
2. Amplifier: To strength the electrical signals.
3. Receiver: To convert the amplified electrical signals back into sound waves, which are then transmitted into the ear canal.
4. Power Source: Small batteries cells.

A rich variety of hearing aid are available and each comes with its unique advantages. You can choose from all sorts of hearing aids with different designs, sizes and acoustic characteristics depending on the degree of your hearing impairment and your personal requirements. In this way, your can better your hearing performance and pursue a “sound” life.

Hearing aids are classified into 2 types based on the fitting position.

In-the-ear (ITE)

ITE is completely put inside the ear. The size of the instrument hinges on the functional requirement and efficacy performance. Common styles include:

CIC (Completely in the canal) The smallest kind of hearing aids which hides completely in your ear and is virtually invisible.
CS (Mini canal) Almost as small as a CIC but with manual controls, e.g. program switch or volume control.
CT (Canal): As an alternative to replace mini-sized hearing aids in case they are not recommended for everyday use.
IT (Concha): Integration of a wide range of supplementary functions, e.g. directional microphone, program switch and volume control.
Advantages: Virtually invisible and comfortable
Conserve battery power
Natural hearing experience
Behind-the-ear (BTE)

BTE is directly put on the ear and transmitted sound into the auditory canal via the ear hook (a soft plastic tube) and ear mould.

Advantages: Versatile (for hearing loss from mild to severe degrees)
Easily operated
Selection and Fitting Procedures

The selection of a suitable hearing aid plays an important role to the rehabilitation of your hearing and has a long lasting effect on your living quality. In this regard, Kowloon Hearing Services Ltd strictly follows the procedures below to help you and your loved ones to choose the most appropriate hearing aids. More importantly, we will always be honored to stand by you for getting through the adapting period.

1.Auditory Check

Comprehensive hearing tests are conducted by our experienced hearing expert to determine the degree and type of hearing impairment.

2.Hearing Aid Selection

Our hearing expert makes suggestions and gives explanation about the hearing aid styles suitable for you in consideration of your hearing test results, living mode, preference, financial budget and physical factors.

3.Ear Mould Custom-making

An impression of your ear is made to custom-make the ear mould if necessary.


When the hearing aid is available, our hearing expert first tunes the instrument according to your hearing loss for a comfortable listening experience. Instructions of the use and maintenance of the hearing aid are given as well.

5.Fitting Trial

You can put on the hearing aid for a few weeks. During this period of trial, you should follow the steps of fitting and adapting to the instrument indoors and outdoors.

6.Post-fitting Follow-up

Our hearing expert offers post-fitting tuning in accordance to your feedback, so as to ensure the efficacy of the hearing aid and your best listening experience.


Proper cleaning and maintenance bring the best performance of functions and longer life span of your hearing aids.

Thorough Cleaning 1.Clean and maintain your hearing aid on a daily basis.
2.Wipe your hearing aid with soft cloth, gauze or a brush along with special cleaner.
3.Do not apply water, alcohol or regular cleaners to avoid damage to the components and circuits.
4.Use a pump to remove water or ear wax from the tube of your ear mould.
Dehumidification 1.Protect your hearing aid from water. Do not use it when taking a bath, swimming or sweating.
2.Dehumidify daily your instrument to prevent moisture from getting into your hearing aid.
3.Dry your hands before touching your hearing aid.
4.If your hearing aid is accidentally dropped into water, take out the battery immediately and have it repaired. Never use a blower to dry the instrument.
Everyday Care 1.Avoid dropping or striking your hearing aid against any hard surface.
2.Replace your BTE hearing aid if cracks or discoloration occurs.
3.Take regular check for your hearing aid.
4.Do not dissemble or fix the hearing aid yourself./td>
Proper Storage 1.Open the battery door of your hearing aid for dehumidification when not using it.
2.Keep your hearing aid away from heat.
3.Keep your hearing aid away from children and pets to avoid damage.
Battery Replacement 1.Keep the battery away from children and pets. Store it in a dry and safe place.
2.Regularly replace the battery once it is out.
3.Discard the battery carefully.
Frequently Asked Questions

Attempting to resolve the doubts about hearing aids, Kowloon Hearing Services Ltd has prepared the following Q & A section for you to grasp more concepts and eliminate confusion. Please feel free to contact us for further professional assistance.

Q: Will hearing aids completely restore my hearing?
A: No, hearing aids can’t restore your lost hearing, but they can let you hear the sounds that you couldn’t before.

Q: Will fitting hearing aids make me look old and infirm?
A: No. Hearing aids nowadays are much smaller that they are nearly undetectable or completely invisible. Many ITE and BTE models are available in fashionable colors and styles.

Q: What is a disposable hearing aid?
A: It is a hearing aid with a built-in battery. The user has to replace the entire instrument after the allotted time of usage.

Q: How much does a hearing aid cost?
A: There are many factors that concern the prices of a hearing aid, including its type, functions, features, accessories and programs. Our hearing expert is delighted to help you with the selection of a suitable hearing aid based on the degree and type of your hearing loss. Generally, the price of an economic digital aid ranges from $2,000 to $20,000, while for analogue aid and BTE, from a few hundred to around $2,000.

Q: Should I put on one or two hearing aids?
A. It depends. For those who have hearing loss due to damage to the inner ear or who have about the same degree of loss in both ears need to wear two hearing aids. If hearing loss only occurs in one ear, you may only need to put one into the impaired ear. However, fitting two aids help you maximize understanding in noisy environment, localize the source of sounds and enhance sound quality. Moreover, having two instruments reduces the risks of deterioration of your hearing impairment, and to prevent your good ear from being inertial. Therefore, it is always the wisest choice to ask hearing experts to recommend whether one or two aids will work best for you.

Q: Why does hearing aid sound so noisy?
A: It could be possible as you may not get used to listening yet after a long lost stimulation of sounds. Your aid also could sound noisy if your hearing aid does not comprise higher capability of noise reduction, or such function need further adjustment, or if there is a change in the status of your hearing impairment.

Q: Why doesn’t my hearing aid seem to help much in noisy environment?
A: This is usually a complaint by analogue aid users. Since this kind of conventional hearing aid tend to pick up background noise together with speech for amplification, the speech is often masked out by noise, which makes communication difficult. Currently available digital aids are good choices for high-resolution suppression of background noise which can greatly enhance your hearing performance in noisy environment.

Q: Why does my hearing aid emit spiky and shrill whistle sounds (feedback)?
A: The annoying sound is caused by the feedback of sound into the microphone, like what happens when you put the microphone too close to the speakers while singing. The two circumstances are of similar principles. For hearing aids, it could be the result of “sound leakage” after improper sizes of ear moulds, fitting positions, loosened ear moulds or turning up of volume. You had better ask the hearing experts to help you custom-make another ear mould, or fine-tune your hearing aid.

Q: Should I replace my hearing aid which has been used for many years?
A: If affordable, you could consider replacing it with today’s digital hearing aids with various kinds of advanced technology – such as noise reduction, environmental detection, suppression of feedback due to sound leakage – that delivers you a clearer and more comfortable listening experience.

Q: Why is the sound quality of my hearing aid getting worse?
A: Worsened hearing, problems arising in the ear mould or tube, and improper maintenance of hearing aids could be the causes. Therefore after fitting the instrument, you ought to have regular hearing and aid check once or twice a year for tracking hearing status and fine-tuning the aid when necessary. Of course you need to pay more attention to the maintenance to extend its life span. For details, please refer to the golden tips for maintenance on our website.

Auditory Health Care

Hearing loss is irreversible. Kowloon Hearing Services Ltd is pleased to share the following tips for protecting auditory health. We cordially hope that you and your loved one could create and enjoy a splendid life together. Treasure your ears from now on!

  1. Minimize everyday noise, like turning down the volume of TV.
  2. Avoid putting on earphones. If you insist, set 1 hour time and 60% of volume allowed as the upper limits for listening via earphones.
  3. Do you expose yourself to noise for a long time, or try to give your ears a break for 10 minutes per hour.
  4. Put on sound-proof earplugs and earmuffs when working in a noisy environment.
  5. Follow the doctor’s instructions. Never attempt drug abuse or overdose to prevent side effects from damaging the inner ear.
  6. Avoid hitting the head or ears to prevent perforation of the tympanic membrane or breaking of ossicles.
  7. Never let your baby lie face up when drinking milk to prevent the milk from getting into the nasopharynx and causing otitis media.
  8. Keep your ears clean. Do not dig your ear randomly or stuff anything into the auditory canal.
  9. Seek medical care as soon as possible when you have fever or upper respiratory tract infection.
  10. Apply water-proof earplugs or cotton ball soaked in petroleum jelly when dabbling to prevent water from getting into your ears.
  11. Regular hearing check once half a year. Conduct hearing tests as early as possible if hearing degradation is suspected.
  12. Take enough rest, do regular exercise and relieve stress. Always keep yourself happy!