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Asked: 2026-05-11T17:35:17+00:00

Background I admit, this question stems from an ultimate lack of deep understanding of

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Background

I admit, this question stems from an ultimate lack of deep understanding of the underlying mathematics involved with digital signal processing; I’m still learning.

I want to take a set of amplitude samples, say 1024 (single channel), and bring them into the frequency domain. Obviously this requires a FFT; no problem there. The problem is that this only gives me frequencies up to the Nyquist frequency or 1024/2.

Question

If I have a stereo signal, can I merge the signals to produce 2048 amplitude samples thus returning 1024 frequency values? I’m looking to get higher resolution in the frequency domain.

So, can this be done and return meaningful frequency data? Is there any other way to take a stereo signal and end up with higher resolutions in the frequency domain?

What I’ve Found So Far

I came across an article that suggested taking the left signal and making it the real value and the right signal and making it the imaginary value of the complex-value for the FFT. This doesn’t make sense to me, perhaps because I don’t understand the math. I did try it, and it seemed to work, but I had signal leakage. So I applied a Hanning window, but that resulted in only 512 usable values after processing.

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1 Answer

  1. Editorial Team

    If the signal you’re analysing were got from a physical signal you can’t do anything.
    Merging the signals into one big array of 2048 samples will be enought to do the math, but the result will be meaningless.

    For an example, make an array of 2048 cells and fill it like this:

    original = int[1024];
    new = int[2048]
    new[2*n] = original[n];
    new[2*n+1] = original[n];

    This way you get a bigger array and an higher frequency, but as your initial data is the same, the result you get won’t be of any help, it will be the same as the original FFT.

    If you need only a higher frequency analysis, you can do 2 things, change the sample rate (I suppose you’re using a sound line in jack) to the max your sound board can do (Mostly 48kHz). Or second, change the aquisition board to some specific hardware (any dedicated usb aquisition board can get up to 1MHz easly).

    Ps: The frequency is 1024/2 times the sampling frequency. Do not forget to multiply the sampling frequency.

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