For years exploring human physiology, anatomy and functions have been an interesting study to reveal the astonishing creation of God. Brain, heart, lungs, circulatory systems, sensory organs yet so complex work in amazing coordination in most simple manner. All this keep the scientists inquisitive to understand more and more deep into understanding body functions and treat the anomalies when the equilibrium is disturbed. Continuous efforts, studies and experiments to improve medical assistance to any disturbance in our body functions has been a continuous process in improving medicine and medical sciences.
Considering one of the most astonishing gifts of hearing which humans are blessed and hence able to communicate by speech is our ears. Actually, all humans connect with each other because of the power to hear each other say. Enjoying music, talking to each other, identifying voice of our acquaintance in a crowded place, hearing background noises, watching movies etc is quiet interesting gift we are blessed to have enjoy our life.
Very often and common observation is that at times this art of hearing suffers from its normal functions and non-conduction of hearing causing an invisible disability leaving us disconnected and isolated from the society. Not able to hear or respond to sound above 60db can be considered as hearing loss disorder. Our ears not only help us to hear but also play major role in maintaining body balance. This disorder of hearing loss and balance maintenance is assessed, diagnosed and rehabilitate by specialized professionals called AUDIOLOGISTS. An audiologist is the right person to advice treatment services along with personalised services to minimise the negative impact of hearing loss and improve quality of life in future. Tests and early intervention help audiologists to guide parents and family members to go through rehabilitative process.
There are few ways to identify hearing loss according to the age of person and the reasons involved. So, it is important for the audiologist to perform the right test at right age of the persons showing signs or symptoms of hearing loss.
It is of utmost importance that as soon as baby is born an audiologist perform a hearing test like a paediatric check’s other vitals of the new born baby. This early detection and henceforth early intervention can lead to minimal loss to quality of life in baby in future years of growth and development.
TYPES OF TESTS
- AUDITORY BRAINSTEM RESPONSE(ABR)
- OTOACOUSTIC EMISSIONS (OAE)
- PURE TONE TESTING
- SPEECH TESTING
- TESTS OF MIDDLE EAR
AUDITORY BRAINSTEM RESPONSE (COMMONLY KNOWN AS ABR)
This test is very effective in new born and small children. As we know that ear is made of three parts- outer ear , middle ear , inner ear. Cochlea which is a part of inner ear is actually screened through this test. The Auditory Brain test tells us that inner ear and brain pathways are working for hearing or not. When a patient fails to respond to basic screening programs should undergo this test to understand if the hearing loss is in the brain or brain pathway. In ABR only one loudness level is checked. Once the baby hears the sound and passes meaning that the brain is monitoring signals correctly. If baby fails the test, then more specific tests are recommended. The test is performed when a baby has eaten well and sleeping. So, to prepare the baby for the test is slightly tedious. The test normally takes 3hours and the electrodes are put on the head in contact with the skin, the other end connected to the computer. Audiologist record the brain wave activity in response to the sounds that he hears through the earphones. Once the test is completed a print out can be taken of the result.
OTOACOUSTIC EMISSIONS (OAE)
This is another very important type of test which is used to find out if inner ear or cochlea are functioning properly. As the name suggests otoacoustic emissions are measured. A small earphone or probe is placed in the ear through which sounds are passed. These sounds cause vibrations present in the hair cells in the inner ear which respond to the sound. If the sound comes back the audiologist can monitor those on the computer screen. The vibrations produces soft sound that echoes back in the middle ear. This sound is the OAE that is measured. In normal hearing the inner ear will produce OAE but if hearing loss is greater than 25-30db then OAE is not produced.
The test can also detect the blockage in middle ear or outer ear. If there is a blockage then no sounds will be able to get through to the inner ear. OAE test is often a part of new born hearing screening program.
It is normally difficult to detect hearing loss in small children or infants. It is always better to get the new born to get the screening for hearing loss. But in India it is not mandatory so quite a big population ignores this test and when a child crosses the age of one year or more and doesn’t respond to sound or signals then parents suddenly panic and start consulting doctors. BERA or Brain Evoked Response Auditory Test is mostly performed on children aged 1 to 3 years. For children smaller than year OAE can be carried out.
BERA can be done on patients only when they are sleeping or calm in a lied down position. Electrodes are placed on patient’s head and also behind the ear. When the procedure is started patient hears various sounds through headphones. BERA measure changes in brain electrical activity (EEG) in the form of acoustic stimuli. If the signal received show abnormalities then it indicates hearing loss.
BERA is expensive then OAE and is not available in all the clinics or audiologists centre across India. It is preferred that if OAE fails then BERA should be taken. In BERA also some advance features are added for more refinement of test.
PURE TONE AUDIOMETRY
The most popular and standard measuring test for hearing loss is Pure Tone Audiometry. Almost every audiologist advice and do this PTA for analyzing the extent of hearing loss. For pure tone audiometry the test is performed in a special sound proof room. A patient is seated inside the room with headphones or earplugs which are connected to a device. This device is operated by a audiologist. Through this device he sends sound of different frequency and volumes to one ear at a time. When a patient hears a sound, he gives a signal to the audiologist by thumbs up or thumbs down if he doesn’t hear any sound. According to the patient’s response he plots a graph which is called AUIOGRAM. Audiogram is a graph that shows the softest sounds patient can hear at different frequencies. Hence this test assesses sensitivity of hearing capacity and calculate the degree of loss. Pure tone audiometry is considered to be the gold standard in the evaluation of auditory sensitivity.
There are different types of audiometers available from simple inexpensive to elaborate and advance expensive diagnostic audiometers. For Pure Tone Audiometry three general methods are used (1) manual audiometry or conventional audiometry (2) automatic or Bekesy audiometry (3) computerised audiometry
Speech sound disorders if not diagnosed at early stage in children affects the child’s ability to communicate at young age but also may lead to later speech and learning disabilities.an audiologist will perform number of tests and will make the patient listen different types of words and will ask them to repeat. This test is called Speech Reception threshold or SRT. This test is usually performed on adults or children who can talk. The results of this test is compared with the Pure Tone tests result to help identify the hearing loss.
Basic speech audiometry uses speech signals to assess a person’s ability to hear speech, discriminate between words and recall words. It has two steps
- Check how loud speech you need to be for you to hear it.
- Other part checks ow clearly you can understand and distinguish different words when you hear as they are spoken Some, number of words are spoken and delivered to patient through earphone at precise decibel intensities and then it is checked how many words patient can recall and repeat.
TEST OF MIDDLE EAR
Also known as tympanometry. It is a objective test not a hearing test. An instrument called pneumatic otoscope is use to diagnose ear infection. The instrument helps the doctor to look into the ear and judge if there is fluid behind the eardrum. The result of tympanometry are represented on a graph called tympanogram. This test is quick and usually painless until and unless eardrum or middle ear is inflamed.