As a matter of fact, the calculated hearing lossthrough audiometry shows a great variation, besidetechnical errors and various conditions at each test.
In order to know the real state of the auditorysense of the human beings and also to find the realhearing acuity of a person, the various range of thehearing acuity of normal ear, conductive and perceptivehearing test and speech hearing test were performedcontinuously.
In order to decide the standard for testing hearingacuity on the basis of the results from the above mentionedtests, how the values tested during the firstthree days should be handled statistically to obtain theapproximate value of the real hearing acuity wasstudied.
A. Pure tone audiometry hearing test.
1) The variation of the hearing acuity in a prolongedperiod of time was larger than that in a day.
The range of the critical limits of the calculatedhearing loss for a long period was as much as±14-25dB in normal ears and showed the largervalues in conductive and perceptive deafness.
2) As to the closest value to the real hearing acuity ofnormal ears and each deafness obtained from thecalculated hearing loss tested on the first, secondand third day, the mean value of ones tested on thesecond and third day was the closest to the realhearing acuity and the critical limits of each cycleand of a+2b+c/4 value were ±10dB and ±7dB.The real hearing acuity in conductive and perceptivedeafness tested at 8000cps could not be obtain.ed as the variation of the calculated hearing loss atthat cycle was very large.
B. Speech perception test.
As to speech reception threshold, the mean valueof ones tested on the second and third day was theclosest to the real hearing acuity and its' critical limitwas ±3dB.
As to speech discrimination score, almost no differenceamong each deafness was observed. In casethe discrimination score was classified into four groupsof 0-25, 26-50, 51-75 and 76-100%, their critical limitsof the mean value of ones obtained on the second andthird day were ±11, 11, 12 and 13% and the differencesamong each group were very small.
C. The standard to know the variation of thehearing acuity.
Above all, the method to know the variation ofthe hearing acuity is to perform above mentionedhearing tests for 3 days before treating the ears and tofind the mean value of ones tested on the second andthird day.
Improvement of aggravation of the hearing acuitycan be decided when the value is larger than 15dB at500, 1000 and 2000cps and also larger than 10dB ata+2b+c/4value in conducthievaer ing test and whenthe degree of speech perception threshold is classifiedinto four groups of 0-25, 26-50, 51-75 and 76-100%and the differences between each group are larger than22, 22, 24 and 26% in speech hearing test.
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