In my previous post I started to discuss what you should expect to happen when you get your hearing tested. I explained the importance of the interview and described the otoscopic examination.
During the otoscopic examination, the clinician checks the outer part of the ear (the part you can see at the sides of your head) to make sure everything looks okay. Then s/he looks down the ear canal to make sure it is clear to proceed with the hearing test. This procedure is completed with an otoscope, a medical device which is used to look into the ears. During this procedure the clinician wants to make sure that the ear canal is free of excessive wax and that there are no skin irritations or other problems that would affect the test results.
The clinician is not performing an otoscopic examination to make a diagnosis but to make sure that the ear drum can be seen and that the ear canal is clear to test. Typically, if the outer ear looks fine and the ear canal is clear of any debris, the clinician will proceed with the hearing tests.
If there appears to be some condition on the outer ear or in the ear canal, the clinician will refer you back to your family doctor for further examination and assistance as required.
Before I continue to explain hearing tests, I want to briefly describe the different parts of the ear and explain how sounds are transmitted to the brain so we know what we are hearing.
The ear is divided into three sections: the outer ear, the middle ear and the inner ear. The outer ear consists of the parts of the ear that you can examine visually and includes the ear canal and the ear drum.
Just beyond the ear drum is the middle ear which is a space about the size of a pea and which houses the three smallest bones in the human body, the malleus (hammer), incus (anvil) and stapes (stirrup). These bones together are referred to as the ossicular chain. The middle ear is attached to the back of the throat by the eustacean tube. The purpose of the middle ear is to direct sound from the outer ear to the middle ear.
The inner ear (cochlea) is a snail-shell shaped, fluid-filled cavity in the temporal bone. It is filled with a special fluid and hundreds of thousands of tiny hair cells which turn the sound waves into electrical messages which are sent along a nerve to the brain.
You can see pictures and diagrams of the human ear by searching, ‘Human Ear’, on Google and then checking Images.
How We Hear: a simple explanation
Sounds are conducted from the environment around us into our ear canals. Sound energy pushes against the ear drum at the end of the ear canal, making the ossicular chain (in the middle ear) move against the oval window which sits between the middle ear and the inner ear. Generally speaking, the movement of the ossicular chain helps to determine the power of the sound which is perceived by the listener. Sound is conducted into the inner ear which translates sound energy into meaningful messages and transmits those messages to the brain.
On completion of the otoscopic examination of the ear canal and ear drum, the clinician may complete impedance testing next. Simply put, impedance testing is an indirect measure of the middle ear.
Impedance testing includes a series of tests which help the clinician to determine if the middle ear is working properly or not and if the ear is able to transmit the sound waves from the environment around us across the middle ear into the inner ear.
The clinician will place a probe into your ear canal. You will feel a slight change in pressure and hear some loud sounds. You are required to sit still and say nothing. The impedance machine will complete the test in less than a minute and record the results so that the clinician can determine the status of your middle ears. The clinician should explain the results of these tests once the hearing assessment is completed.
In a future post, I will review impedance testing in more detail and tell you what different results mean.
Perhaps the most familiar hearing test to our readers is the puretone test or “the test where you hear the beeps and you raise your hand (or push a button or say “beep” every time you hear a ‘beep’). Typically, puretone testing is completed at several frequencies between 250 Hz (like middle C on the piano) to 8000 Hz. Simply put, these frequencies, typically, 250, 500, 1000, 2000, 3000, 4000, 6000 and 8000 Hz., represent the main frequencies which are make up the components of speech in the English language.
The puretone test determines your ‘threshold of hearing’ or the lowest level where you just barely hear sounds (the beeps). Now-a-days, puretone testing is completed through insert ear phones which are held in your ear by soft foam inserts rather than the more traditional head phones. Generally speaking, the sounds are presented through the inserts and you indicate that you hear them by responding via raising your hand, pushing a button or saying, “I hear it”.
The clinician records the softest level when you indicate that you hear the sounds and records your responses in a graph called an audiogram. S/he will be able to compare your hearing graph to a graph of normal hearing to determine your degree of hearing loss. Again, at the end of the hearing assessment, the clinician will explain what the results on the audiogram mean and will answer any questions you might have about the audiogram.
You can see pictures and diagrams of the audiogram by searching, ‘Audiogram’, on Google and then checking Images. In a future post, I will describe the audiogram and tell you what information we get from reviewing the results on the audiogram.
As 2012 winds down, I want to thank you for reading my monthly posts. I hope you find them helpful and interesting. I wish you a warm and safe holiday season and wish you all the best in 2013. More posts to come in 2013! Cheers!
Glen Sutherland, MCISc
Please note that the information in this blog is presented for the purpose of providing information and should not be used for medical diagnosis or treatment nor should it be used in place of medical advice from your doctor or hearing health care professional.