A hearing aid is not always effective to all kinds of deafness. However, it is not easy to predict its suitability in each deaf case, but it should be decided by the user himself by wearing it in his daily life. As the results of measurements of threshold of audibility with a tuning forks, audiometer and speech and as the results of articulation tests, the following facts have been found out. 1)A hearing aid is:a)effective in all cases of conductive deafness. b)effective in some cases of perceptive deafness, and not so in others. 2)In conductive deafness:a)effective when hearing loss is 20-40db(however, conversation is possible without a hearing aid. )b)remarkably effective when hearing loss is 40-60db. (conversation becomes possible by using the machine, otherwise it is very difficult. )3)When the maximum score of articulation is:a)more than 80%, conversation becomes possible by using the hearing aid. b)60-80%, conversation is slightly difficult even with a hearing aid. c)under 60%, conversation is quite difficult even with a hearing aid, and needs lip reading. d)impossible A hearing aid can be used only to supplement lip reading. 4)A hearing aid is of no use for the total deafness. 5)A hearing aid is no good if it causes dizziness, pain in ears, or unpleasantness.
