白噪声
参考 Wikipedia。
白噪声是一种功率谱密度为常数的随机信号（或随机过程），即此信号在各个频段上的功率一致。理想的白噪声具有无限带宽，因而其能量是无限大的。
在离散时间信号中，白噪声可以看做是由均值为零、方差有限的不相关随机变量离散采样得到的信号序列。
需要注意的是，相关性和概率分布是两个不同的概念。“白”仅意味着信号是不相关的，白噪声的定义除了要求均值为零外并没有对信号应当服从的概率分布作出任何假设。
谱白化
参考 StackExchange。
一些讨论
What is meant by “spectral whitening” in DSP ?
Spectral whitening is usually an attempt to make the spectrum of the signal “more uniform”. One reason this might be a good thing to do is that it can have the effect of making the autocorrelation of the signal “narrower” (and closer to a Dirac delta, for discrete-time signals). This can help localize in time.
Where might spectral whitening be useful in audio processing or analysis ?
If you are trying to localize (in time) the onset of a sound, then it’s possible that spectral whitening can improve this. It’s also possible that it can reduce the SNR.
