Lankford, James E.
M.A. (Master of Arts)
Department of Speech Communication
The purpose of the present study was to determine: 1) if the difficulty of the LOT Test is beyond the ability of children in the eight to ten year old age group. 2) if the LOT will misclassify youngsters in this age range who actually have normal hearing sensitivity. The Lengthened Off-Time (LOT) Test, developed by Hattler (1970), is a modification of Bekesy audiometry in which the duty cycle of the pulsed signal has been altered from 50 per cent to 20 per cent (200 msec, on-time, 800 msec, off-time). The clinical efficiency of the LOT Test using an adult population was found to be 98.3 per cent overall. The test correctly identified 99.6 per cent of the organically-impaired patients and 95.5 per cent of the nonorganic patients. The LOT Test was administered to 100 normal-hearing subjects ranging in age from eight to ten years. Each subject was selected from a public school system and had hearing sensitivity better than 20 dB HTL at 500 Hz, 1000 Hz, 2000 Hz, and 4000 Hz. Testing was conducted at the Northern Illinois University Speech and Hearing Clinic in a sound-treated IAC room using a Grason-Stadler Bekesy Audiometer (Model K-800). A series of Tektronix equipment was connected to the Bekesy audiometer to alter the duty cycle to 200 msec, on-time and 800 msec. off-time as required for the LOT Test. The test was delivered to each subject at 1000Hz, 2000 Hz, 4000 Hz, and 500 Hz, respectively. Each subject was instructed to depress the hand switch of the audiometer as soon as he heard the sound and to release the switch as soon as the sound disappeared. His response controlled the movements of a pen across a sheet of graph paper. The youngster first tracked his threshold while listening to the LOT signal, and then to the continuous signal. Analysis of the data involved taking the difference of the means of the two tracings (for the LOT signal and continuous signal). A difference of 5.5 dB or greater was considered as being indicative of a nonorganic hearing loss (positive result). Ninety-nine subjects were able to perform the required task. The LOT misclassified (false positive result) only 4 per cent of the normal-hearing children at 1000 Hz. At other frequencies not used by Hattler, the LOT misclassified 3 per cent at 2000 Hz and at 4000 Hz, and 14 per cent at 500 Hz; with an overall misclassification rate of 21 per cent. Results of the investigation indicate that: 1) the LOT Test is not too difficult for the eight-to-ten year old population, 2) a greater than 6.0 dB criterion should be utilized rather than the approximate 5.5 dB criterion suggested by Hattler (1971), 3) only a 2 per cent false positive rate is expected at 1000 Hz, 2000 Hz, and 4000 Hz if the 6.0 dB criterion is employed, 4) 500 Hz should not be used as a test frequency because of the relatively high false positive rate (14 per cent), 5) an overall false positive rate of 5 per cent is obtained for the frequencies of 1000 Hz, 2000 Hz, and 4000 Hz.
Behnke, Charles R., "The Lot test and school-age children" (1973). Graduate Research Theses & Dissertations. 5989.
vii, 44 pages
Northern Illinois University
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