回顧行為及電生理反應測量遮蔽差異值及周邊聽力損失的影響

A Review of the Effects of Hearing Loss on Masking Level Differences

羅意琪(Yi-Chi Lo)

《台灣聽力語言學會雜誌》 32期 (2014/04) Pp. 57-68

https://doi.org/10.6143/JSLHAT.2014.04.03

摘要

遮蔽差異值（masking-level difference, MLD）是一種雙耳聆聽優勢（binaural advantage）的現象，可用來判斷中樞聽覺系統的異常，正常成年人的500 Hz遮蔽差異值約為10~15 dB。此數值是否因為受試者的周邊聽力損失程度影響，一直沒有定論。由於聽力損失常常伴隨年齡的增長而產生，因此過去關於聽力損失對遮蔽差異值影響的相關研究，個案多數為年長者，而年長者同時又伴隨著中樞聽覺處理的問題，因此過去的研究結果均無法排除遮蔽差異值的變化，是因為聽覺系統老化或是周邊聽力損失所造成。遮蔽差異值可以由個案行為反應測得，也可以由電生理測試中的晚潛時值反應測量，本文將回顧遮蔽差異值的相關背景和影響此數值的因素，並且介紹如何以電生理聽力測試中的晚潛時值反應測量遮蔽差異值，進一步回顧周邊聽力損失對遮蔽差異值的影響。本文最後引用近期相關研究，以模擬聽力損失的技術讓正常聽力的成人聆聽，控制個案聽力損失的程度和聽力圖的圖形，由於正常年輕人有著健全的聽覺神經路徑，藉由這個技術可以排除中樞聽覺傳導路徑所造成的影響，進而單獨分析聽覺閾值改變對於遮蔽差異值的影響。基本上而言，雙側對稱型高頻率聽力損失對於遮蔽差異值的影響不大，然而聽力損失程度越大且越接近低頻率，對遮蔽差異值的影響就越多。當臨床上欲使用遮蔽差異值做為中樞聽覺功能的評估工具，對於同時伴有周邊聽損的個案，瞭解高頻聽損和其程度對遮蔽差異值的影響，可以在結果的解釋時，明白在何種聽損程度和測試方法下，可以忽略高頻聽損所造成的影響。

關鍵字

遮蔽差異值 ； 聽覺晚潛時測試 ； 模擬聽力損失 ； 中樞聽覺處理 ； 雙耳聽覺功能

並列摘要

The masking-level difference (MLD) is an index of binaural hearing that determines the ability to perceive tones in noise based on temporal cues in background noise. A robust MLD is obtained by measuring binaural thresholds to tones in different phase conditions (homophasic vs. heterophasic) in a background of noise. People with normal auditory function have 8 ~ 15 dB lower thresholds for 500 Hz signals in heterophasic conditions compared to homophasic conditions. The homophasic condition, SoNo, is that signals and noise are presented in phase (phase angle is zero) between two ears. The heterophasic condition, SπNo, is that signals are presented out of phase (phase angle is 180 degree) and noises is presented in phase between two ears. The magnitude of the MLD was also confirmed with the electrophysiological MLD which has been measured with the P2 responses of the auditory late latency responses (ALLR) in young adults with normal hearing. However, the hearing loss is always as a confounding factor to the MLD was obtained from people with auditory pathology. Thus, the effects of hearing loss on the MLDs are still unclear. The recent study used noise masker to simulate the hearing sensitivity elevation to normal hearing adults. The advantage of using simulated hearing loss was to have better control of levels of hearing loss and hearing configuration among individuals. In addition, no etiological or pathological factors were involved. This article will introduce how to record the MLDs from auditory evoke potentials and review the results of hearing loss on MLDs. Finally, the effect of simulated high-frequency hearing loss on 500 Hz MLDs will be discussed.

並列關鍵字

Masking-level differences ； Auditory late latency response ； Simulated hearing loss ； Temporal auditory processing ； Binaural hearing

參考文獻

Bocca, E.,Antonelli, A. R.(1976).Masking level difference: Another tool for the evaluation of peripheral and cortical defects.International Journal of Audiology.15,480-487.

Butler, R. A.,Kluskens, L.(1971).The influence of phase inversion on the auditory evoked response.International Journal of Audiology.10,353-357.

Cherry, E. C.(1953).Some experiments on the recognition of speech, with one or with two ears.The Journal of the Acoustical Society of America.25,975-979.

Durrant, J. D.(2004).Simulated hearing loss via masking: Research and heuristic applications.Seminar in Hearing.25,25-37.

Fowler, C. G.,Mikami, C. M.(1992).The late auditory evoked potential masking-level difference as a function of noise level.Journal of Speech, Language, and Hearing Research.35,216-221.