![]() The sample segments were categorized into 2 groups, as follows: (A) samples for which the recorded sound amplitude went from a maximum to a minimum as the TF was rotated and (B) samples for which the amplitude went from a minimum to a maximum. In preprocessing, the recording was split by performing a cut at each point where the sound amplitude reached a maximum and at each point where it reached a minimum, resulting in a total of 229 sample segments. This process was repeated for 20 iterations. ![]() The recording was made as the vibrating TF was rotated by hand until the recorded sound amplitude reached background noise level. The device screen was video recorded for subsequent manual extraction of the measurement data for analysis.Ĭlinical setup of experiment with handheld tuning fork with long axis parallel to baseline of the measuring instrument. Measurements-sound amplitude values of the vibrating TF-were displayed on the measuring device. The excited TF was held with its long axis parallel to the line of the device’s “bottom end” (where its speakers and microphone are located) at a distance of 4 cm ( Figure 1). The background noise level of the examination room was measured as ranging from 33.20 to 33.90 dB. The accuracy and sensitivity of the device microphone were checked for both frequency and amplitude detection in an audiobooth: the results of the sound frequency and amplitude detected by the audiobooth headphones were compared against those registered on the device (frequencies: 500, 1000, 2000 Hz amplitudes: 40, 50, 60, 70 dB). Ltd was used to measure sound amplitudes at various angles of the vibrating tuning fork placed by the device microphone. Mimicking the human ear, an iPhone 8 (software 12.4.1 Apple) running the application DeclibelX:dB Sound Level Meter Version 8.1.3 by Sky Paw Co. More specifically, the objective was to establish the range of differences in amplitude between a TF positioned at the “best” and “worst” angles. Thus, the research objective was to measure the extent to which the perception of sound amplitude is affected by variations in TF angle relative to the ear during the air conduction part of the Rinne test. Incorrectly positioning the tuning fork within cancellation angles by the ear during the Rinne test will change the perception of sound amplitude and can thus potentially alter test results. Variability derives from where and how the TF is placed next to the ear when evaluating air conductions. 6, 7Īs mentioned above, Rinne test results are highly dependent on the conditions of individual iterations of the test. Nevertheless, all locations of the cancellation are within the hyperbolic borders extending from the TF, 5 somewhere around the 45° and 135° angles of each half turn. 4 The angles at which the cancellation effect occurs vary depending on the size of the TF and the distance between TF and receiver (microphone or ear). During a whole single rotation of the TF around its long axis, the sound perceived from a fixed point gets quieter and then louder 4 times (2 cycles per half turn of the symmetrical device). ![]() This is perceived by the examinee as a significant reduction in sound amplitude (ie, muting). Close to the TF, destructive interference occurs, that is, acoustic waves are cancelled out (the cancellation effect). Each vibrating tine creates 2 longitudinal waves in the surrounding air, which propagate and interfere with each other. It has been proved that the sound from a vibrating tuning fork decays over time and the sound amplitudes are unevenly distributed around the TF. The physical nature of a vibrating tuning fork has been investigated in numerous physical studies explaining the nature of the sound spectrum, sound wave propagation, and sound wave interferences. Therefore, subtle differences in sound amplitude resulting from variations in TF position by the ear during air conduction testing may change the test result, given that perception via bone conduction does not vary depending on TF position. The Rinne test is based on the acoustic impressions of the examinee and compares the lowest audible sound amplitudes for air and bone conduction. 1, 2 There are variations in how the Rinne test is performed, 3 and it is thus considered highly individually dependent, mostly due to differences in how the tuning fork (TF) is placed relative to the ear when evaluating air conductions. Of the wide spectrum of existing clinical tuning fork tests, the Rinne test is a very simple and reliable way to verify conductive hearing impairment.
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