The 过程 by which one 信号 is used to modify another The 控制 信号 is referred to as the 'carrier' and the 控制 信号 as the 'modulator' It is of the greatest importance in both 声波 合成 and 信号 处理

The two 主要 参数 of a 声波 to which 调制 is commonly applied are those of 振幅 响度 and 频率 振幅 调制 of a 信号 causes changes in 响度 in that 信号 If the 控制 信号 is a slow regular 波形 e g a 正弦 波 the result is a tremolo - 类似 to and often confused with 颤音 except that there is no 音高 deviation Once the 频率 of the 调制波（器） is raised above 10 to 15 赫兹（he zi） the tremolo amalgamates into a 复杂 声波 with 加 频率 components 派生 from the 音高 of 载 and 调制波（器） An irregular or 瞬态 控制 信号 is 通常 联合 with 包络 生成

频率 调制 causes the 音高 of the 载 to rise and fall according to the 形状 of the modulating 波形 If this is as above a slow regular 波形 the result is 颤音 if the 深 of the 调制 is 低 otherwise becoming a wide siren-like 效果（效应） If the modulating 波形 is a 系列 of 离散 steps the result is a 系列 of 离散 音高 尤其 复杂 声 arise when the 频率 of the 调制波（器） is close to or even 较高 than that of the 载 源 - Richard Dobson 1992 A 字典 of 电子 and 算機/计算机 樂/乐 技术 牛津 University Press

環/环 调制 allows for the 总和 and difference of two 输入 频率 to be 合并 to 创作 a new 声波 Often one of these 频率 is at a sub-audio 级 allowing the 创作 of a 声波 of two 类似 频率 经常 with noisy textural 特征