MAGIC

Play-audiometry is a well-established method in pediatric audiology. However, the test procedure, in which the child must be continuously observant, is exhausting, and the task (usually placing a peg in a pegboard) varies only slightly. In contrast, image-based and self-paced test procedures can considerably enhance the child’s attentiveness. MAGIC is an image-based, self-controlled test which provides a playful alternative to conventional pure-tone audiometry. The test is especially designed for pre-school and school children but can be used for other cooperative subjects as well. Please note that for subjects who are not expected to be able to perform the test or are not able to react to the
sound in a proper way, a DPOAE or ASSR Threshold measurement is advised.
Two MAGIC workflows are available:
– MAGIC Screen allows quick hearing screening at user-selectable frequencies and levels. If multiple levels are selected, the algorithm starts at the lowest level and proceeds to the next higher level each time the tone is not heard.
– MAGIC Audio allows hearing threshold determination at user-selectable frequencies with an automatically controlled bracketing algorithm. Mute tones are included for detecting incorrect inputs of the subject.
MAGIC can be performed at standard audiometric frequencies from 250 Hz to 8 kHz. Different animals represent different frequencies (cow = 250 Hz, bear = 500 Hz, elephant = 1 kHz, cat = 2 kHz, sheep = 3 kHz, mouse = 4 kHz, bird = 5 or 6 kHz, dolphin = 8 kHz – see Figure 4).

Figure 1: MAGIC animals (from left to right: cow, bear, elephant, cat, sheep, mouse, bird, and dolphin)

Each animal is presented in three variants: neutral to start the sound presentation, healthy and sick for indicating the two conditions heard and not heard, respectively (see Figure 5). The self-controlled workflow needs extensive explanation to the subject. An introductory story is recommended for explaining the task and for motivating the subject to be tested. The subject shall take the role of a doctor whose task is to diagnose healthy and sick animals based on whether or not they make a sound, respectively. This can also help to ease the pressure on the subject, because it is not him/her who is being diagnosed, but he/she will diagnose the animals’ ability to produce sounds.
Via touch-screen the subject controls the sound presentation and the response if the sound was heard (healthy animal) or not (sick animal). The examiner explains the test procedure during the instruction phase, supervises the measurement, and assists the subject if indicated. The examiner can also intervene in the measurement procedure at any time or can do a retest at any frequency if necessary (MAGIC Audio).

PRACTICAL USE
Select MAGIC from the module selection screen. Select the preset that you would like to use. If necessary, change the parameters (e.g. test mode, frequency, screening levels (MAGIC Screen) / test level range (MAGIC Audio), stimulus type) and preset name as required. For some subjects (e.g. children) a warble tone may be more interesting than a pure-tone and hence may be preferred. Also, for subjects with a tonal tinnitus a warble-tone may distinguish the stimulus from the tinnitus more efficiently.
Make sure that a valid transducer is connected (e.g. headphone, insert earphones, bone conductor) and select the test ear (Right+Left: sequential measurement of right and left ear for each frequency). The measurement can be started with the introduction phase (if enabled in the settings) or the test phase.
It is recommended to start with the instruction phase. For instruction tell the subject that his/her task is to be a doctor now. Some animals will produce a sound because they are healthy and happy (shown cheering with hands up) and some animals will not produce a sound because they are sick (shown wearing a scarf). The subject in the role as a doctor shall find out which animals are healthy and which are sick. To find out whether the animal produces a tone or not the neutral animal shall be pressed (see Figure 5 – ①). The response shall be given by pressing the respective healthy ③ or sick ② animal. A response is only accepted after the belly of the neutral animal has been pressed, i.e.
after tone presentation. The instruction phase starts with a stimulus at a user-definable initial level (MAGIC Audio) or at a fixed level determined by the device (MAGIC screen). The second stimulus is presented with a level 10 dB lower (if first response was heard). Finally, a mute tone is presented in order to accustom the subject to the situation that also no sound may occur.

Figure 2: MAGIC user interface (left: tone presentation and response; middle/right: animal selection).

After the instruction phase the test phase starts. Depending on age and physical/mental abilities, the test phase may be conducted completely self-controlled (i.e. subject enters response) or with assistance of the examiner. Supervision by a qualified examiner is recommended at all times.
The progress of the test procedure may be visualized by a shelf, from which the current test animal is selected (option for MAGIC Audio). During the test, please check if the subject conducts the test appropriately. If there is any hint that the subject does not understand the workflow (e.g. pressing healthy animal after mute tone presentation or pressing the screen randomly) you may restart the test or repeat the instruction phase in-between (option in settings ⑤) (MAGIC Audio). Also a previous patient response can be undone when pressing the undo button ④ in the footer (press the power on/off switch to make the footer visible).
In the header, information about the current test status including stimulus levels and subject’s response is provided (see Table 3). For example, the header in Figure 5 shows that the test is in the instruction phase with a tone presented at 50 dB HL when pressing the animal’s belly. The previous stimulus, which was presented at 60 dB HL, was heard by the subject. If you suspect that the subject might take advantage of the header information, turn off the current level information in the module settings (also possible during the test for MAGIC Audio via the settings button ⑤).

At the beginning of the test phase and after finishing a test run at a frequency, the subject is allowed to select a new animal (see Figure 5 – right). The order in which the different animals are selected is up to the operator (i.e. tested subject or examiner).

After the test is finished, for MAGIC Screen the result is shown as a table (see Figure 6) with heard ④, not heard ⑥, and skipped/not tested ⑤ symbols. For MAGIC Audio, the result is shown as an audiogram. For MAGIC Audio it is possible to retest specific frequencies. A retest may be indicated if an incorrect response of the subject is shown. An incorrect response is represented by a “?” in the audiogram below the affected frequency. The number of incorrect responses is shown below the “?” ⑦. Another indication for retesting a frequency may be an outlier in the audiogram. In the MAGIC
Audio result screen you can see test details by pressing in the audiogram the respective frequency.
The responses at the selected frequency are shown (in this case example: 25 dB HL: heard, 5 dB HL: not heard, 15 dB HL: heard, mute: not heard, 10 dB HL: heard; test run finished and threshold determined to be 10 dB HL). The gray line marks the minimum level configured in the module settings.
Please note that during this test the footer is hidden. You may activate the footer by pressing the power on/off switch briefly.

Figure 3: MAGIC result (left: MAGIC Screen; middle: MAGIC Audio; right: MAGIC Audio detail)

STUDY RESULTS
The feasibility and reliability of MAGIC was investigated in children in a multi-center study conducted at the Department for Communication Disorders, ENT department of the University of Mainz Medical School´s hospital (Germany), at the ENT clinic of Klinikum rechts der Isar, Technische Universität München (Germany), and at Cyprus Audiology Centre Nicosia (Cyprus) (Schirkonyer et al., 2010b, 2011). MAGIC tests were conducted in 108 children aged between 3;6 and 11;11 years at frequencies 0.5, 1, 2, 4 kHz (n = 82) and additionally at 0.25, 3, 6, 8 kHz (n = 26). Additionally, hearing threshold estimation by means of DPOAE I/O functions were performed in 36 children from the collective.
DPOAE I/O functions were recorded at frequencies f2 = 1, 1.5, 2, 3, 4 and 6 kHz with primary tone levels L2 in the range from 10 to 65 dB SPL. Thresholds were estimated by linear regression analysis. Primary tone levels L1 and L2 were set according to the scissor paradigm. The frequency ratio f2/f1 was 1.2. Both MAGIC and DPOAE I/O functions were measured with Sentiero. For comparison, playaudiometry pure-tone thresholds were determined at the corresponding frequencies. There was a highly significant (p<0.001) correlation between image-based (MAGIC) and play-audiometry thresholds. The correlation coefficient (n = 1247) was r = 0.73. The histogram of the difference
between image-based and play-audiometry thresholds showed normal distribution. The mean difference amounted to -1.5 ± 9.6 dB. Test time per frequency (one ear) was on average about 30 s, ranging from 14 to 91 s. Test time decreased with increasing age. Also, MAGIC pure-tone thresholds and estimated DPOAE thresholds were highly significant (p<0.005) with a correlation coefficient of r = 0.60.