Getting Better Results from Audiometric Tests
The ear is a two-way street, not just picking up incoming sound but also creating sound itself. If your ear picks up the top two notes in a chord it will finish the remaining notes itself. This basic principle is referred to as an otoacoustic emission – it is basis for audiometric tests used in measuring hearing damage.
Researchers have now found a way to make these audiometric tests even better – the secret is to use bone conduction to transmit sounds into the ear. The human ear is tuned just like an instrument – it reacts to the major scale. This is what makes the audiometric test effective and accurate. Whenever the ear hears the top two notes of a major chord, it will produce the root note of the chord in response, and a small and extremely sensitive microphone can be used to pick up this sound.
This test can therefore be used to show if inner ear function is working properly and to ascertain whether or not there is anything wrong with the hair cells inside. The test is particularly effective for testing the hearing of young children and infants, since they cannot be expected to respond to sound in a hearing test like an adult can.
In the past this test was performed by putting a speaker next to each ear along with the recording microphone. However, problems occurred when the speakers did not work correctly or interfered with one another – the response of the ear needs to be recorded accurately if medical professionals are to know whether or not an infant’s hearing is working properly.
Sending vibrations directly into the bone behind the ear reduces the likelihood of mechanical failure inadvertently influencing the results of the test. This process has been likened to using a tuning fork – the inner ear is isolated in such a way that issues with the middle ear do not alter the test. Now that this study has been completed, it will likely progress to clinical trials.