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D-0116493-B (OM015) – PC850 Operating Manual
4.5.2. COMPUTER TESTING
This is a method of automatic audiometry based on the Hughson and Westlake method and undertaken
automatically by the instrument. The level is increased in 5dB steps until a response is obtained from the
patient and decreased in 10 dB steps until no response occurs. The process is repeated until, depending
upon the criteria selected for recording a threshold (see Section 4.4), the instrument will record a threshold at
that particular frequency. The PC850 then continues to the next test frequency and so on to complete the
test on both ears. When completed the test data is transferred to Audibase.
4.5.3. BÉKÉSKY TEST
This is a method of automatic audiometry devised by Von Bekesy (1947) using pure tone stimuli to track
auditory thresholds.
This application is known as discrete frequency Bekesy testing and the principle behind the test is that the
patient adjusts the presented level according to his hearing threshold. The decibel level decreases when the
patient presses the response switch upon hearing the presented tone. Conversely when the patient can no
longer hear the presented tone, he will release the response switch therefore allowing the level to increase
until the presented tone is heard again. The level changes are in 2.5dB steps.
When a number of these "peaks" and "valleys" have been consistently performed, the PC850 will calculate
an average to the nearest dB and display this as the hearing threshold for that particular frequency. The
PC850 then continues to the next test frequency and so on to complete the test on both ears.
4.5.4. SINGLE FREQUENCY TEST
The PC850 provides the facility to repeat a test at a specified single frequency and add the results into the
overall audiogram result. This feature is useful for situations where one particular frequency has proved
problematic.
4.5.5. MIXED TESTING
This allows manual testing of any frequencies when an automatic test has been unable to determine a
threshold. The combined results are then transferred to Audibase.
4.6. INITIATING A TEST VIA COMPUTER
Start the Audibase application, and with reference to the user manual either establish a new a patient, or
access and display details of an existing patient.
Use the left mouse button to click on the Launch Test icon in the Audibase toolbar.
Alternatively use the “Test > Launch Test” drop-down menu selection at the top of the Audibase window.
A new window will open for the PC850 software. If the patient has more than one set of audiometric results
stored in Audibase the most recent audiogram is transferred and displayed in the PC850 window.
The serial number and calibration date of the connected PC850 audiometer is shown at the bottom right of
the PC850 window along with the test type currently selected.
The test type last used is remembered; if this was a manual test the procedures described in Section 4.4
may be followed; if this was an automatic test the following dialogue box will be displayed:
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