Takeuchi Y
Department of Otolaryngology, Kitasato University, Medical School, Kanagawa.
Nihon Jibiinkoka Gakkai Kaiho. 1992 Nov;95(11):1744-58. doi: 10.3950/jibiinkoka.95.1744.
A new strategic masking technique, namely the ABC method, has been developed. In performing this method of measuring thresholds of bone-conduction, the vibrator is placed at the forehead with both ears occluded by air-conduction earphones. One of the earphones is for masking noise and the other is a dummy which balances out the occlusive effect of the test ear against the nontest ear. The ABC method is based on the ABC rule that, in bone-conduction testing, the effective masking noise level necessary to block out the nontest ear can be calculated by a simple equation: right AC (A) + left AC (B)--unmasked BCu (C) under the assumption that the BCu belongs to the nontest ear. In some cases of hearing loss, the above noise level might produce overmasking, then an additive safety noise level, BCu + Interaural Attenuation, is employed. This method offers testers step by step directions which consist of indications of the noise level and a criterion for determining whether the measured bone-conduction is free from cross hearing and overmasking for the given configuration of air-conduction of both ears, BCu, and the masking noise level. Compared to the well known Plato method, in which measurements of thresholds are repeated at several masking noise levels in order to find a single bone-conduction threshold, the ABC method can essentially find the threshold at only one masking noise level. Therefore the ABC method makes it possible to save a great deal of time in performing bone conduction testing.
一种新的策略性掩蔽技术，即ABC方法，已经被开发出来。在执行这种测量骨导阈值的方法时，将振动器置于前额，双耳用气导耳机堵塞。其中一个耳机用于掩蔽噪声，另一个是平衡测试耳对非测试耳的堵塞效应的假耳机。ABC方法基于ABC规则，即在骨导测试中，阻断非测试耳所需的有效掩蔽噪声水平可以通过一个简单的公式计算：右气导（A）+左气导（B）-未掩蔽的骨导阈值（C），假设骨导阈值属于非测试耳。在某些听力损失的情况下，上述噪声水平可能会产生过度掩蔽，此时采用附加安全噪声水平，即骨导阈值+耳间衰减。该方法为测试人员提供了逐步的指导，包括噪声水平的指示以及对于给定的双耳气导配置、骨导阈值和掩蔽噪声水平，确定所测量的骨导是否不存在交叉听力和过度掩蔽的标准。与著名的柏拉图方法相比，在柏拉图方法中，为了找到单个骨导阈值，需要在几个掩蔽噪声水平下重复测量阈值，而ABC方法基本上只在一个掩蔽噪声水平下就能找到阈值。因此，ABC方法使得在进行骨导测试时能够节省大量时间。
