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i am trying to make a real time audio spectrum display. My problem is microphone gives an single analog output, but to apply fft we need atleast 8 inputs to fft. how can i convert a single input from microphone to atleast 8 values for using fft??????

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closed as unclear what you're asking by Marcus Müller, Peter K. Jun 23 '17 at 12:29

Please clarify your specific problem or add additional details to highlight exactly what you need. As it's currently written, it’s hard to tell exactly what you're asking. See the How to Ask page for help clarifying this question. If this question can be reworded to fit the rules in the help center, please edit the question.

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    $\begingroup$ Hi, welcome to signals.SE! Your question is very unclear. I think you're missing either the fact that your microphone gives you a voltage signal that changes over time, and hence, your soundcard gives you a sequence of numbers, which you then can process, or you're completely missing what you need the FFT for. In either case, you might want to look at what a soundcard does and what you're interested in in a little more depth before asking a less confused question! $\endgroup$ – Marcus Müller Jun 23 '17 at 12:00
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The FFT will process the samples bs time of your analog signal. For 8 consecutive samples in time from your sound file you will get 8 uniformly spaced frequency bins in your FFT ranging from DC up to 7/8 of your sampling rate, and each bin will have a frequency resolution of 1/T Hz where T is the time duration of your 8 samples. I think you will see from that, for your application, you will want a lot more samples (assuming you are interested in seeing more frequencies). Also learn about windowing where you taper the magnitude of your analog signal prior to taking the FFT and how that will effect the dynamic range and frequency resolution.

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