我怎样才能在赫兹DFT / FFT的输出频率？ [英] How can I get DFT/FFT output frequencies in Hertz?

问题描述

我想开发音符探测器作为我的学位项目，我想从头开始做。我已经写了code为.WAV文件，该文件从提取音频音乐文件的所有信息，并给了我振幅的结果。

I want to develop musical notes detector as my degree project and I want to do it from scratch. I have written code for ".wav" file which extracts all info from that audio music file and gives me amplitude as a result.

然后我写了一个code的DFT - 它给了我输出作为一个复数，其中轴线之一（实/虚）是幅度/幅度等是相

Then I have written a code for DFT - it gives me output as a complex number where one of the axis (real/imaginary) is amplitude/magnitude and other is Phase.

现在我想在频率上回答这个问题（在赫兹不是矢量），所以我可以检查我是否DFT给我适当的输出与否。如何将我的DFT输出转换为频率？

Now the question I want the answer in frequency (in Hertz not in vector) so I can check whether my DFT gives me the proper output or not. How can i convert my DFT output into frequency ?

我要在C语言中code这一点，我不希望使用任何内置库

I have to code this in C language and I don't want to use any built-in library

推荐答案

您需要找到高峰的大小的然后制定出相应的频率：

You need to find the peak magnitude then work out the corresponding frequency:

• 计算每个DFT输出纸盒的大小： =幅度的sqrt（重*重新+ IM * IM）


• 找到的最大震级的bin，调用它的指数最大电流。


• 计算这个箱子的等效频率：频率=最大电流* Fs的/ N ，这里 FS =采样率（赫兹）和 N =没有在FFT点。

• calculate the magnitude of each DFT output bin: magnitude = sqrt(re*re+im*im)
• find the bin with the largest magnitude, call its index i_max.
• calculate the equivalent frequency of this bin: freq = i_max * Fs / N, here Fs = sample rate (Hz) and N = no of points in FFT.

请参阅this解答获取如何仓索引和频率相关的更详细的解释。

See this answer for a more detailed explanation of how bin indices and frequency are related.

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