The Nature of Audiology Pure-Tone Testing Explained
In order to treat a hearing impairment effectively, its precise nature and extent must first be determined and audiology employs pure tone testing to achieve this. Simply put, this is a form of examination in which the subject is exposed to a series of electronically generated sounds at frequencies in the audible range. These start at around 125 Hertz in the bass register and extend to 8000 Hertz in the treble region.
Each note is generated at gradually decreasing volumes measured in decibels and starting from a point where the subject hears it clearly. This continues until the subject no longer indicates that he or she is able to hear it. The results are plotted on a graph known as an audiogram in which each point represents the volume at which the subject was able to clearly discern each of the generated notes.
The test is performed for each ear and it is customary for the person who is conducting the examination to record both sets of results on the same audiogram but using differing symbols, such as circles and crosses, to differentiate the performance of the right and left ears.
In a subject whose hearing is normal, each of the frequencies presented during any audiology examination that utilises pure-tone testing will have been readily detected at a volume of 20 decibels or less. One of the more common deviations from the norm, particularly among the elderly is that of high frequency impairment. In these cases, the subject can detect the lower notes comfortably and the graph lies in the normal region but, as the notes become higher, marked increases in volume are required and the latter segment of the audiogram falls well below the normal level of detectability.
In other instances, the impairment may be more comprehensive and affecting the patient’s audition at all frequencies. The result is a graph in which all of the points on the audiogram fall well below the critical 20 decibel level.
This, of course, is just one facet of a full diagnostic examination that may be begin by examining the ear canal with an otoscope to ensure it is clear of wax and debris that might interfere. Another important preliminary step is the use of immittance audiometry to determine that the eardrum is able to move normally. This process is known as tympanometry.
The ability to hear clearly is important to almost every aspect of our lifestyles. At The Ear Institute, we provide trained and experienced specialists who employ the most advanced diagnostic techniques and equipment currently available. This ensures that when undergoing examinations such as audiology pure-tone testing our patients receive the best possible attention.