An 电子 treatment applied to a 声音 to 'expand' its 动态 范围（排列） 扩张 is 通常 used to 反转 the 效果 of 压缩 in the 录音 过程 e g as part of a 噪音 简化 系统 but it can also be used on its own to 降低 the 噪音 content of a 信号 by progressively attenuating 信号 at a 低 电平/级别 where 噪音 is most apparent The 行为 of an 扩张器 is 类似 to that of a 噪音 gate the two 效果 often being 合并 in a single 单元 The 组合 of 压缩 and 扩张 in a single 单元 is 通常 termed a 'compander' 源 - Richard Dobson 1992 A 词典 of 电子 and 计算机 音乐 技术 牛津 University Press