Modified tone decay test(Rosenberg´s procedure) was carried out for 20 cases of normal ear, 20 cases of conductive hearing impairment and 40 cases of sensori-neural hearing impairment.
The results were as followings;
1. No tone decay was observed at all frequencies in the cases of normal and conductive hearing impairment and in the cases of sensori-neural impairment, the amount of tone decay was 1.6 dB at 1000 Hz., 4. 1 dB at 2000 Hz. and 7.6 dB at 4000 Hz.
2. In the case of cerebral tumor, significant amount of tone decay was observed; 20 dB at 2000 Hz. and 25 dB at 4000 Hz.
3. The case which the amount of tone decay exceeded 15 dB, was not observed in normal and was only one(5%) at 4000 Hz. in the cases of conductive hearing impairment.
And the cases in which the amount of tone decay exceeded 15 dB among the sensori-neural impairments were one case (2.5%) at 500 Hz., 2 cases (5%) at 1000 Hz, 4 cases (10%) at 2000 Hz. and 13 cases (42.5%) at 4000 Hz.
4. The cases in which the amount of tone decay exceeded 15 dB among the sensori-neural impairments were as followings;
i) Two cases of acoustic trauma; One at 2000 Hz. and the other at 4000 Hz.
ii) 4 cases (57.1 %) at 4000 Hz. in the cases of presbycusis.
iii) One case (12.5%) at 4000 Hz. in the cases of Meniere´s syndrome.
iv) 11 cases of undetermined origin; One case (5.5 %) at 500 Hz., 2 cases (11.1 %) at 1000 Hz., 2cases (11.1%) at 2000 Hz. and 6 cases (33.3%) at 4000 Hz.
Consequently, 13 cases of sensori-neural impairment showed over 15 dB decay at 4000 Hz.; among them 10 cases were presbycusis and undetermined origin.
One case of acoustic trauma and 2 cases of undetermined origin showed over 15 dB decay at 2000 Hz. Over 15 dB. decay at 500 Hz and 1000 Hz was observed only in the cases of undetermined origin.
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