Audiometer

Everything you need to Know about audiometer

A personal device used to examine the listening threshold of a person is an audiometer. Audiometric testing techniques are used by a professionally trained person or audiologist to determine the limit and the degree of hearing loss. The results of the audiometer examination guide the prescription of proper medical treatment or befitting hearing aid. Different frequencies and tones are presented at many levels to the patient's ears. The level at which the person can only hear the stimulus is the hearing threshold. There are different types of equipment that can be used to conduct different hearing tests. There is a vast difference in diagnostic audiometer, screening audiometer, and clinical audiometer. A screening audiometer finds potential listening deficiency. A full diagnostic assessment is necessary when screening fails. A diagnostic audiometer has more functions than the screening audiometer. It identifies and quantifies the disorders and their origin. A response from the patient is a requirement as an audiometer is a subjective testing device.

Audiometer types 

  1. A screening audiometer is a screening test used to assess the potential of deficiency. The most common choice for assessment of hearing at several set frequencies is pure tone audiometry. They are small and portable.
  2. Diagnostic and clinical tests are needed when a patient has failed a screening. It is useful in examining and determining the kinds and causes of hearing loss. An audiologist performs this specific test.
  3. Computer based audiometer can change signal intensity and frequency according to patient response and give automatic results in print form.
  4. Finally, the automatic audiometer can change the signal intensity according to the response of the patient automatically.

Audiometer parts:

The following are the parts of the instruments:

  • Oscillator
  • Attenuator
  • Interrupter switch
  • Stimulus
  • Output selector
  • Input selector
  • Talkback

History of audiometers

By the second half of the 19th century, a wide range of audiometers was invented and used in the market. They were known as induction coil audiometers. Its invention followed the development of the induction coil in 1849. Arthur Hartmann designed an 'auditory chart' in 1885. Hence, to measure up the keenness of the hearing, Carl Seashore introduced the audiometer as an instrument in 1899. At Western Electronics, his machine became the basis of the audiometer. Latter, a German physicist, Max Wien, conceived the concept and idea of frequency vs. amplitude in 1903. In 1978, David Kemp reported that the ear's sound energy is detectable in the canal. Finally, the system of measurement and detection OAEs was produced commercially for the first time in 1988.

Indications

The result of an audiometry test shows the functioning of the ears. The intensity and tone of the sound are both examined. It can also check the balance issues and the problems related to the function of the inner ears.

Some common and essential indications are:

Congenital disabilities

Inherited issues like otosclerosis occur when abnormalities increase in the bone's growth, becoming a cause of the problem within the structure of the ear.

Ear infections

Infection due to viruses and bacteria can cause swelling and accumulation of fluid, causing acute middle ear infection called otitis media.

Injuries

Falling accidents, sports injuries, fighting can all cause damage to the ear.

Meniere's disease

The disease is a disorder of the inner ear that can cause problems in listening and balance issues.

Exposure to loud noises

The industrial noises, traffic, and more can damage the eardrum.

Fetal Alcohol syndrome

The mother's consumption of alcohol during pregnancy can cause a disturbance in mental and physical growth.

Family history of deafness 

Genetic history of deafness can be another known cause.

Persistent circulation of fetal

This is a failure of systemic flow or pulmonary circulation.

Congenital infections

This is an infection transmitted to a baby from the mother during pregnancy or delivery

Cranial nerve VIII lesion

This is also known as the vestibulocochlear nerve, which transmits sound and maintains equilibrium.

An audiologist can identify infants with any of the above indicators. Exposure to loud noises regularly can become a reason for hearing loss. Louder sounds higher than 85 decibels can become a reason for hearing loss after a few hours. If a person is regularly exposed to loud music or industrial noise, they must use the protection of foam earplugs. When hair cells are not functioning correctly in the cochlea, then sensorineural loss occurs. It may also occur when the nerve that sends sound information to the brain is damaged. Usually, this type of failure is permanent and not curable. It has different levels: mild, moderate, or severe.

Contraindications

The following is the list of conditions in which audiometry is contraindicated:

  • The patient is less than seven months old
  • There is any discharge from the ear
  • Tympanic membrane swell and red investigate through otoscopy
  • Soreness or tenderness in the ear canal
  • Any foreign body in the ear canal
  • Excessive accumulation of ear wax
  • History of ear surgery

Complications

The process is very safe and secure. There are no risks associated with this procedure. It is a non-invasive diagnosis and screening tool which does not require many precautionary measures to avoid complications. The only little complexity is the lack of proper response from the patient, which hinders getting the desired and accurate results of the test.

General Specifications

There are several designs of audiometers found in the market, with different specifications; however, we are going to cite some specifications, which should be accurate enough.

Dimension

 Length: 370mm

 Weight: 290mm

  Height: 180mm

Weight: 3.5kg

Display: 7TFT color display

Resolution: 480 x 272

User Interface: Multilingual

Power supply: 110-240 volts

Power consumption: 9 watts

How audiometers work

There are no additional preparations needed for audiometry tests other than booking an audiologist appointment and following the instructions from the audiologist.

Few tests are involved in audiometry. Pure tone test measures the quieter sound that a person can hear at different levels and pitches. An audiometer is the instrument used in this test in which sound plays via headphones. An audiologist or his assistant performs a variety of sounds like tones and speeches into one ear and with appropriate intervals to examine the ranges of frequency. The audiologist gives instructions for each sound. 

Another specific test is to determine the listening abilities of a person by differentiation of speech from background noises. A sample of the sound plays to the patient's ears, and then the patient is asked to repeat the words. Word recognition is significant and helpful in diagnosis.

A tuning fork can be useful in checking the ability to hear the vibrations through ears. For this purpose, a bone oscillator that is a mechanical device that transmits vibration just like a tuning fork is useful. All the tests are harmless and do not create any discomfort or pain. The duration of the tests can be an hour. 

After all the tests, the audiologist will review the results with the affected person. The audiologist will tell about the precautionary measures depending on the test results, including tone and volume, such as the use of foaming ear plugs around loud noises, or wearing a hearing aid.

Market leaders

Here is a list of some companies which provide this instrument globally. Different types and designs of this instrument are available and supplied by these companies. They cost between $800 and $5000.

1- Grason Stadler

2-Interacoustics

3-Sanibel Supply

4-Maico Diagnostics

5- e3 Diagnostics

6-Medical Expo

7-Benson Medical Instruments

8-Otometrics company

Conclusion

The invention of the audiometer has great importance in the medical profession. Deafness and hearing loss can cause permanent disability in the life of a person. The ENT uses the audiometer as a diagnostic and screening tool for the assessment of the patient. So, on-time diagnosis can help to save this sense from permanent damage. Many people lose their ability to understand words in old age. Many diseases like mumps, meningitis, tumors, infections, congenital diseases cause decreased listening ability. After testing, an audiologist can tell the severity and loss of hearing ability and determine what preventive measures and prescribe any hearing aid tool. The audiogram is a graphical representation of sound frequency, which helps in the diagnosis of severity of hearing loss. Different types of audiogram patterns are seen to varying kinds of hearing loss, like in Meniere's disease low-frequency pattern, in noise notched pattern, in nerve injury, downward high-frequency loss pattern. It helps to find out the cause and treatment according to reports results.