In this test, senseless monosyllabic sounds of Japanese speech are used. Generally, 100 sounds are used in one test. As to the test-distance, the point where the difference between normal hearing and slightly impaired hearing begins to be noticed, is determined as standard distance at each test room by each tester. In proportion as the noise of the test room increases, the standard distance is getting shorter. The experiments show that the result of the test is reliable when the standard distance of test room is longer than 1/3 of the standard distance in the sound proof room. The degree of hearing difficulty is expressed in the name of "mis-hearing rate, " which indicates the proportion of the sum of hearing loss and mis-hearing to the tested words' number in percentage. From the results obtained by the above described method, I could classify the patients into 5 categories according to the percentage of hearing loss:
normal hearing, less than 5%; very slight difficulty, 5-10%; slight difficulty, 20-30%; moderate difficulty, more than 50%; severe difficulty, 100%.