Maico Ero Scan Pro Operating Instructions Manual

Contents

Maico Ero Scan Pro Operating Instructions Manual Manual pdf 6 page image

Operating Instructions3The SPL and frequencies of the test tones and the averaging time used to process the signals can bedetermined by the tester through adjustable settings maintained in static memory within the ERO•SCANPro instrument.What Frequency Range of Hearing is Estimated?DPOAEs: Approximately 1.5 kHz to 12 kHz (depending on the frequency range selected). Since thehealth of the hair cells in the region of the f 2 test frequency are estimated, and a) the 2f 1-f 2 emissionfrequency is at about six-tenths of the f 2 frequency, b) emissions tend to be weak below 600 Hz or so,and c) the ambient noise tends to be highest at low frequencies, the lowest f 2 test frequency that canbe routinely measured is about 1 kHz. TEOAEs: Roughly 500 Hz to 4 kHz. TEOAEs can be reliablyrecorded at lower frequencies than DPOAEs, but cannot be measured reliably above 4 kHz.1.3 TympanometryWhat is tympanometry?Tympanometry is the objective measurement of middle ear mobility (compliance) and pressure withinthe middle ear system. During the test, a probe tone (226 or 1,000 Hz) is presented to the ear canal bymeans of the Tymp•OAE Probe. This tone is used to measure the change in compliance in the middleear system while the air pressure is varied automatically from a positive value (+200 daPa) to a negativevalue (-400 daPa max.).How is compliance measured?Maximum compliance of the middle ear system occurs when the pressure in the middle ear cavity isequal to the pressure in the external auditory canal. This is the highest peak of the curve as it is recordedon the chart. The position of the peak on the horizontal axis and on the vertical axis of the chart willprovide diagnostic information regarding the function of the middle ear system. Examples of normaland abnormal tympanograms can be found in a later section of this manual.What other measurements are calculated?Gradient calculations are reported as the tympanogramwidth at half of peak compliance expressed in daPa. A“limits” box is available on both the display and printoutto aid in diagnosis. Compliance is measured with respectto an equivalent volume of air, with the scientific quantitymilliliter (ml). Air pressure is measured in deca-Pascals(daPa).What does tympanometry tell us?The impedance measurement assists in diagnosing of thecondition of the middle ear and can therefore not becompared directly with other audiometric tests such assound or speech audiometry which assists in themeasurement of hearing. Furthermore, the impedancemeasurement is an objective measuring method whichdoes not depend on the cooperation of the test person and can therefore not be falsified by thepatient.The impedance measurement examines the acoustic resistance of the middle ear. If the eardrum is hit bya sound, part of the sound is absorbed and sent via middle ear to the inner ear while the other part ofthe sound is reflected. The stiffer the eardrum is the more sound is reflected and the less sound reachesthe inner ear. Inside the probe of the impedance measuring instrument a small loudspeaker is installedwhich emits a low frequency sound through a tube (Figure 3) into the auditory canal before theeardrum. Another tube is connected to the microphone inside the probe which receives the sound.Together with a third tube, all three are inserted deeply into the ear canal and are made airtight against