Distortion-Product Otoacoustic Emissions Suppression Tuning Test

變頻耳聲傳射的抑制測驗

林鴻清(Hung-Ching Lin) ； 徐銘燦(Ming-Tsan Shu) ； D. T. Kemp

《聽語會刊》 12期 (1996/12) Pp. 25-32

摘要

耳聲傳射(OAEs)可被另一個聲音所抑制，並且這個抑制現象可表現耳蝸的頻率選擇性。本研究有幾個目的，第一、評估在正常耳，其變頻耳聲傳射的抑制測驗(D P suppression test)可否以四個固定的f3來完成？ 第二、測試此以簡化的檢查方式可否能在短時間內完成？ 第三、評估此一測驗可否代表正常耳蝸的頻率選擇性？
20個正常人的雙耳接受測試，在變頻耳聲傳射中，其f2/f1之比率為1.25。其中f2分別固定在1KHz，2KHz及4KHz。其L1之音量為65dB SPL，L2之音量為60dB SPL。接著4個f3予以適當地選擇與固定。此一6 dB的suppression tuning curve(STC)可由此四個固定的f3來完成。
在正常耳，平均STC的測試成功率為82%，一個測試約需時5至10分鐘。當f2由1KHz 增至2KHz及4KHz時，可見STC的尖點需要較高的音量，其平均數值分別是60.8，61.5及64.9 dB SPL。每一個平均STC均是一個不對稱的V字型；且其高頻區間之斜率較低頻區間為大。並且當f2由1KHz往2KHz及4KHz增加時，此一STC形狀變的更尖形。
此一變頻耳聲傳射的抑制測驗(DP suppression test)在正常耳獲得大致成功；且其測試時間並不長。且它可表現出正常耳蝸的頻率選擇性。故在將來，其有可能成為臨床研究之重要工具。

並列摘要

Otoacoustic mission can be suppressed by an additional stimulus and this suppression shows frequency selectivity. There are several aims of this study. The first is to assess if distortion-product (DP) suppression test with 4 fixed f3 areas can be achieved in normal subjects. The second is to check if this simple DP suppression test can be completed in a reasonable time. The third is to assess if this simple test represents normal cochlea frequency selectivity.
DP suppression tuning tests were performed in 20 normally hearing subjects. DPOAE were elicited by fl and t2, with a ratio of f2/fl=1.25. The f2 was fixed at 1 KHz, 2KHz and 4KHz respectively for 1 KHz, 2KHz and 4KHz suppression test. Ll =65 and L2=60 dB SPL were used. Then, 4 f3 frequency were selected randomly, but reasonably. The 6 dB isosuppression tuning curve can be achieved from these 4 fixed f3 areas.
The average success rate of STC measurement was 82% for normal subjects. About 5-10 minutes was required for each DP suppression test. With increasing primary frequency, higher intensity of suppression level at STC tip was needed and the mean was 60.8, 61.5 and 64.9 dB SPL for test with f2= 1KHz, f2=2KHz and f2=4KHz respectively. Asymmetrical V-shaped STCs were plotted for each frequency tested. The high-frequency slope was steeper than low-frequency in the 3 average STCs. The shape of the average STC became sharper progressively with increasing primary frequency.
The DP suppression test method with 4 fixed sites was successful in normal subjects. The test time required was not too long for clinical use. This test apparently represented normal cochlea frequency selectivity, too. It will be possible that this test may become a useful tool for clinical research.