正火FFT数据（FFTW） [英] Normalising FFT data (FFTW)

问题描述

使用FFTW我已计算归一化的.wav文件数据的FFT。我有点困惑，我应该怎么正常化FFT输出，但是。我一直用这似乎明显对我来说，这仅仅是由最高的FFT幅度来划分方法。我已经1 / N，并建议N / 2，但是，（在这里我假设N = FFT的大小）看到师。如何做这些工作的正常化因素是什么？似乎没有对我来说，这些因素与实际数据之间的关系直观的 - 所以我缺少什么

Using FFTW I have been computing the FFT of normalized .wav file data. I am a bit confused as to how I should normalise the FFT output, however. I have been using the method which seemed obvious to me, which is simply to divide by the highest FFT magnitude. I have seen division by 1/N and N/2 recommended, however (where I assume N = FFT size). How do these work as normalisation factors? There doesn't seem to me to be an intuitive relation between these factors and the actual data - so what am I missing?

提前巨大的感谢有这方面的帮助。

Huge thanks in advance for any help on this.

最佳，
圣油

推荐答案

令人惊讶的是用于FFT和IFFT，至少只要缩放而言没有单一的一致的定义，但是对于大多数实现（包括FFTW）需要由1 / N在向前的方向扩展，并且在相反的方向不结垢。

Surprisingly there is no single agreed definition for the FFT and the IFFT, at least as far as scaling is concerned, but for most implementations (including FFTW) you need to scale by 1/N in the forward direction, and there is no scaling in the reverse direction.

通常（出于性能原因），你会想与任何其他问题，比如你的A / D转换增益，窗口增益校正系数等忍下这个比例因子，这样你只需要申请一个组合的比例因子您的FFT出纸槽。另外，如果你是刚刚发生，也就是说，在dB的功率谱，那么你可以改正你从你的功率谱箱减去一个dB值。

Usually (for performance reasons) you will want to lump this scaling factor in with any other corrections, such as your A/D gain, window gain correction factor, etc, so that you just have one combined scale factor to apply to your FFT output bins. Alternatively if you are just generating, say, a power spectrum in dB then you can make the correction a single dB value that you subtract from your power spectrum bins.

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