增益 is a measure of how loudly the 声波 plays back You can change 增益 just like you can turn the volume up or down on your TV or 立体声

A change of 增益 over a period of 时间 is known as a 淡化 for 例如 a fade-in can take place at the beginning of a 作品 or at the introduction of a new 声波 If a change in 增益 is done carefully it can make a great difference to the way in which someone hears and 理解 your 作曲