声 波 can both add together and subtract from one another When 声波 add together they are 描述 as being ‘in phase’ with one another When 声波 subtract from one another they are 描述 as being ‘out of phase’ This cancelling out of the soundwave can result in some very strange 声 效果 and is sometimes 故意 applied to 声 相位 cancellation the subtraction of one 声 from another can happen when the same 声 is played from 多 扬声器 and the 声波 meet or when 声 reflect off of a 表面 and the 反射 meets the 原始/原创 波前