The hearing test, or consultation, should be a pleasant and informative experience. The variety of possible tests that a hearing aid audiologist can perform is huge. The general structure of the initial consultation will normally follow the basic structure as follows:
The hearing aid audiologist will ask lots of questions about your hearing, your health and other associated topics. It is important that the patient is open and honest as there may be important factors that need to be considered. Certain conditions can be identified and the appropriate treatment or referral can be offered. If hearing aids are to be ultimately prescribed, they need to deliver the expected requirements. In most cases, the hearing aid audiologist will ask for a friend or relative to be present at this appointment. This can be particularly useful as hearing loss can affect the lives of other people as well. A patient may overlook certain key issues or down-play significant problems.
Pure tone audiometry (air conduction)
The patient will be instructed to raise their hand, indicate or press a button when they hear a sound. Headphones will be placed on the patients ears and a variety of different pitched sounds will be played to them at different levels. The headphones will be connected to an audiometer. The main purpose of this test is to establish the quietest sound a person can hear in each ear. This is known as their threshold of hearing. A “normal” healthy average threshold should score 0dB on all the frequencies tested. Zero decibels doesn’t actually mean they can hear a stimulus of “nothing” as the decibel scale is actually a logarithmic conversion of the Pascal measurement of sound pressure. Indeed some people can actually hear negative dB measurements such as -10dB (which are not really negative values at all).
Bone conduction audiometry
This is a similar test to the air conduction test above. The instructions to the patient are the same but the headphones consist of a headband that has a vibrating pad on one side and nothing on the other. This vibrating pad is placed against the bone behind the ear (mastoid) and the sound travels directly through the skull and into the inner ear (cochlea). This effectively bypasses the outer and middle ear. The purpose of this test is to ascertain the location and nature of the hearing loss. If the hearing loss is a result of problems with just the outer or middle ear then the bone conduction test results may show a normal or “zero” reading whereas the air conduction test would show a hearing loss. If there is a difference between the air conduction reading and the bone conduction reading then this is called an “air-bone gap” and is an indication of outer or middle ear problems. This type of hearing loss is called a conductive loss as the sound is being impeded from conducting along the auditory pathway to the inner ear. If the air conduction and bone conduction readings both show a hearing loss then the patient is most likely suffering a “nerve deafness” relating to the inner ear and is much more common.
As mentioned, there are many other tests that can be performed. In certain circumstances it may be possible for the ear on the other side to hear the sound being presented to one side. In this case it may be necessary for audiologist to play a “masking” sound to the non-test ear whilst the other ear is being tested. This usually sounds like a rushing noise rather than a beep.