Biological Calibration for Web-Based Hearing Tests: Evaluation of the Methods

Abstract

BackgroundOnline hearing tests conducted in home settings on a personal computer (PC) require prior calibration. Biological calibration consists of approximating the reference sound level via the hearing threshold of a person with normal hearing.ObjectiveThe objective of this study was to identify the error of the proposed methods of biological calibration, their duration, and the subjective difficulty in conducting these tests via PC.MethodsSeven methods have been proposed for measuring the calibration coefficients. All measurements were performed in reference to the hearing threshold of a normal-hearing person. Three methods were proposed for determining the reference sound level on the basis of these calibration coefficients. Methods were compared for the estimated error, duration, and difficulty of the calibration. Web-based self-assessed measurements of the calibration coefficients were carried out in 3 series: (1) at a otolaryngology clinic, (2) at the participant’s home, and (3) again at the clinic. Additionally, in series 1 and 3, pure-tone audiometry was conducted and series 3 was followed by an offline questionnaire concerning the difficulty of the calibration. Participants were recruited offline from coworkers of the Department and Clinic of Otolaryngology, Wroclaw Medical University, Poland.ResultsAll 25 participants, aged 22-35 years (median 27) completed all tests and filled in the questionnaire. The smallest standard deviation of the calibration coefficient in the test-retest measurement was obtained at the level of 3.87 dB (95% CI 3.52-4.29) for the modulated signal presented in accordance with the rules of Bekesy’s audiometry. The method is characterized by moderate duration time and a relatively simple procedure. The simplest and shortest method was the method of self-adjustment of the sound volume to the barely audible level. In the test-retest measurement, the deviation of this method equaled 4.97 dB (95% CI 4.53-5.51). Among methods determining the reference sound level, the levels determined independently for each frequency revealed the smallest error. The estimated standard deviations of the difference in the hearing threshold between the examination conducted on a biologically calibrated PC and pure-tone audiometry varied from 7.27 dB (95% CI 6.71-7.93) to 10.38 dB (95% CI 9.11-12.03), depending on the calibration method.ConclusionsIn this study, an analysis of biological calibration was performed and the presented results included calibration error, calibration time, and calibration difficulty. These values determine potential applications of Web-based hearing tests conducted in home settings and are decisive factors when selecting the calibration method. If there are no substantial time limitations, it is advisable to use Bekesy method and determine the reference sound level independently at each frequency because this approach is characterized by the lowest error.

Hearing Tests on Mobile Devices: Evaluation of the Reference Sound Level by Means of Biological Calibration

“…The intensity of a stimulus decreases as long as the button is pressed and increases when released, yielding a near-threshold zigzag tracing. The calibration was carried out using a pulsed tone, within the frequency band 125 Hz to 16 kHz, at frequency change 1 octave/minute and intensity change 2 dB/second [ 24 ]. It took 7 minutes to complete the calibration.…”

“…The “Hearing Test” app was developed based on Web page–embedded Java applet ported to Android system. The Java applets had previously been used in the research on validity evaluation of self-test Web-based pure-tone audiometry [ 2 ] and in the research on biological calibration methods for Web-based hearing tests [ 24 ]. During the trial, based on preliminary analyses, the number of calibrations required to calculate predefined calibration coefficients was reduced (from 100 to 16; September 6, 2014).…”

“…The device and its components may be calibrated in a laboratory [ 3 - 5 , 10 , 22 , 23 ]. Alternatively, calibration may be conducted in home settings by means of the biological method, that is, in relation to the hearing threshold of a normal-hearing person [ 1 , 2 , 11 , 24 ]. The devices calibrated in laboratory conditions exhibit the smallest error, and for those devices, there is no significant statistical difference compared with the pure-tone audiometry [ 4 , 5 , 10 , 22 ].…”

“…By far, the biggest error is found in the case of biological calibration. The mean standard error of the biological calibration method based on the Bekesy audiometry is estimated at 4.90 dB [ 24 ]. However, biological calibration does not require specialized equipment, and its application significantly improves the accessibility of the examination.…”

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“…Subjects performed the test while wearing hearing aid or cochlear implant. For audiometric testing we used webbased software (e-audiologia.pl) [32,33] and Sennheiser HD 280 Professional headphones. Vocal audiometry is a procedure aimed to test subject's ability to understand common and simple words.…”