Audiometry (2. LF UK)

Introduction
Audiometry is the measurement of the range and sensitivity of a person's sense of hearing. Hearing occurs when sound waves stimulate the nerves of the inner ear causing the nerves to deliver signals to the brain. Air conduction is when sound waves travel to the inner ear through the ear canal, eardrum, and bones of the middle ear. On the other hand, bone conduction is when sound waves pass through the bones around and behind the ear.

The intensity of sound is measured in decibels (dB):
 * A whisper is around 20 dB


 * Loud music is around 80 to 120 dB

Sounds greater than 85 dB can cause hearing loss after a few hours. Louder sounds can cause immediate pain, and hearing loss can develop in a very short time. The tone of sound is measured in Hertz (Hz), and the normal range of human hearing is about 20 to 20,000 Hz.
 * A jet engine is around 140 to 180 dB

Importance in clinical medicine
Audiometry is involved in a myriad of branches in medicine. Its main function is to diagnose and prevent or improve patients’ hearing disorders. There are many reasons for taking an audiometry test such as either when the patient notices a deficiency in their hearing ability or under routine screening. Causes for hear loss can be: Areas of Medicine in which Audiometry is used:
 * Age related
 * Genetic conditions (otosclerosis involves abnormal growth around the stapes ossicle resulting in deterioration in hearing ability)
 * Constant contact with loud sounds like listening to loud music or side effects of patient’s occupation
 * 1) Audiology: it’s the study of hearing and balance and its disorders i.e. whether the patient can register the normal range of frequencies. Audiologists are directly linked to rehabilitation services that provide devices such as hearing aids or cochlear implants (when disorder is localized in the inner ear) to overcome his/ her debilitation
 * 2) Phoniatrics and speech-language pathologist: “the medical speciality dealing with voice, speech, language, hearing and swallowing disorders”, according to the Union of European Phoniatricians.
 * 3) Otorhinolaryngology: the combined specialties of diseases of the ear, nose, pharynx, and larynx, including diseases of the head and neck, tracheobronchial tree, and oesophagus.

Literature Review
Particularly, the literature has much to speak of audiometry.

Advantages and Disadvantages:
In fact, audiometry has a couple of advantages and disadvantages. When it comes to the advantages, audiometers are highly beneficial devices that enhance the audiologist’s capability of testing someone’s hearing abilities. It is crucial in diagnosing hearing defects and issues of patients. Moreover, the audiologist would have very high control over the whole measuring process and would keep the audiometer under his full regulation. As for the disadvantages, the results obtained are quite not specific or accurate, despite the fact that one would obtain highly reasonable thresholds from the audiometer. Hence, all noise regulations and assessments should preferably be done by trained audiologists to lessen the chance of error occurrence. Additionally, the examiner is unable to assess more than one patient at a time or carry out another task. He cannot basically leave it recording and must be in full control of the audiometer.

How does it work?
Audiometry assessment works in cooperation with the three main parts of our ear (outer, middle and inner ears). It helps perceive if the patient has any defect to the nerve or cochlea (sensorineural hearing loss) or damage to the eardrum or tiny bones of the ear: incus, malleus and stapes (conductive hearing loss).

A diagram shows all specific parts of the ear that assess in transferring the sound into the brain.

To illustrate, the outer ear collects and centralizes audible sound to the eardrum. The sound causes a vibration of the eardrum, which is passed to the incus, malleus and stapes of middle ear. This causes the vibration of the cochlea, and eventually the fluid and hair cells of the cochlea start vibrating. As the hair cells tremble, nerve signals are delivered to the brain.The brain will consequently perceive it as sound.

During the test, the patient puts on headphones (in case of air conduction) or bone conductor (in case of bone conduction). These are connected to the audiometer. The audiometer sends a series of sounds that differ according to their pitch and loudness to the headphones or bone conductor. The loudness, or sound intensity, that the patient perceives is measured in decibels (dB). Each ear of the patient will be assessed individually. Every time the patient hears a tone, he presses a button to notify the audiologist of hearing the sound. To exemplify, the audiologist controls the volume of the sound delivered and decreases it until the patients hears nothing. The examiner will display a technically louder sound so that the patient would be able to hear again. The process will be repeatedly carried on and on with sounds at a high frequency each time to accurately determine the patient’s threshold of hearing.

Risks involved in its use:
As for the risk the test carries, there are no major risks on the patient.

Ethical issues:
Speaking of ethics, audiometry does not raise any ethical issues.

Equipment
Screening audiometer MAICO ST20 with correspondent: NOTE : The examined person should sit in an acoustically isolated booth.
 * 1) Headphones with red (right) and blue (left) side (evaluates hearing-loss in air-conduction)
 * 2) Bone conductor (evaluates hearing-loss in bone-conduction)
 * 3) Response switch
 * 4) Audiogram form

Methodology
1. Turn on the audiometer (1)

2. Get acquainted with all the buttons of the frontal panel

3. To start the procedure set the slider level control (9) at 10 dB and 1 kHz

Air conduction

4. The examinee may now put the headphones in the correct side; red part in the right ear and blue in the left, eliminating any obstructions (like hair, glasses…)

5. After filling the header of the audiogram form (11), place it on the two holding pins

6. Press key (2) until the according LED lights for air conduction turn on

7. Begin with the ear in which the patient perceives to have better hearing using (6) or (7);

8. Instruction to the person being tested: Please press the patient response switch whenever the test tone is just audible

9. From now on remember to only register the lowest sound intensity that the patient responds to in each frequency; use a red circle o for the right and a blue cross × for left ear

10. Press the signal-interrupter key (8) when you get a auditory response from the examined person (red LED blinks (12)) or not at all (stays red)

11. Starting at - 10dB increase the intensity level with the slider level control gradually, until the patient indicates that he/she can just hear the test tone, press the interrupter key and mark the audiogram form

12. Set the slider level control back to -10 dB, select the next frequency by using the left and right “arrows” (13) and (14), increase the level again

13. Test through the other frequencies in the same way

14. After completing the 10 dB intensity level, the tester decreases intensity by 5 dB using (9) and presents the tone again to all frequencies, and so on

15. If the examined person signals hearing of testing signal, slightly decrease the sound intensity level again until you have your chart complete

16. Choose the poorer ear and repeat the hearing threshold test

17. After the test connect the correspondent dots and crosses with a continuous line

Bone conduction

18. Press key (2) this time for bone conduction

19. Select the ear you want to test first on the panel (6) (7); preferably the same as in step 7.

20. When putting the bone conductor, make sure the flat, circular side is placed on the mastoid process (bony prominence behind the ear) while the other side stays in front of the ear

21. Follow the same steps of the air conduction process

22.This time use as reference a red > for the right and a blue < for left ear

23. Do the same with the other ear and remember to turn the conductor upside down

24. Connect the symbols with a intermittent line this time

25. Turn the machine off (1)



Conclusion
Some of the future developments will introduce and encompass more efficient and better audiometric booths with greater noise mitigation and lower weight due to new materials as in the S40 booth designed by SIBEL S.A. Furthermore, audiometers will be more automated and precise as the computational power grows each year consequently leading to more flexibility with difficult cases, in addition to better and more accurate diagnosis of hearing loss and other diseases of the ear. Moreover, this also means that physicians will not have to spend their time doing routine tasks which are attributed to the automation; as a consequence this will allow them to be focused solely on analyzing and interpreting the data.