本文所述规程提供了测试配电变压器作为音频噪声源的说明。这些测试测量变压器在通信电路中产生电噪声的程度，通信电路与变压器供电的电源电路在物理上是平行的。 变压器具有其他铁芯设备所共有的特性，即使音频谐波电流在变压器的供电电路中流动。这些电流的大小以及可能产生的干扰的大小根据变压器的设计以及励磁电压而变化。本规程中所述的试验为变压器制造商、用户和其他行业人士提供了一种标准方法，以便更好地评估可用的设计选择，并朝着与谐波励磁电流水平有关的行业目标发展，用Ia？T（电流x电话影响系数[TIF]）。

The practice described herein provides instruction for the testing of distribution transformers as sources of voice frequency noise. These tests measure the degree to which a transformer may contribute to electrical noise in communication circuits that are physically paralleling the power-supply circuits feeding the transformer. Transformers have a characteristic that is common to other iron-core devices of causing harmonic currents at voice frequencies to flow in supply circuits to the transformers. The magnitude of these currents, and of interference that may result, varies according to the design of the transformer as well as the excitation voltage. The tests described in this practice provide a standard method for use by the transformer manufacturer, user, and others in industry for the purpose of better evaluating the design choices that are available and moving toward industry objectives with regard to levels of harmonic exciting current expressed as I · T (current x telephone influence factor [TIF]).