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Asked: 2026-05-26T10:17:08+00:00

I’m using a FFT on audio data to output an analyzer, like you’d see

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I’m using a FFT on audio data to output an analyzer, like you’d see in Winamp or Windows Media Player. However the output doesn’t look that great. I’m plotting using a logarithmic scale and I average the linear results from the FFT into the corresponding logarithmic bins. As an example, I’m using bins like:

16k,8k,4k,2k,1k,500,250,125,62,31,15 [hz]

Then I plot the magnitude (dB) against frequency [hz]. The graph definitely ‘reacts’ to the music, and I can see the response of a drum sample or a high pitched voice. But the graph is very ‘saturated’ close to the lower frequencies, and overall doesn’t look much like what you see in applications, which tend to be more evenly distributed. I feel that apps that display visual output tend to do different things to the data to make it look better.

What things could I do to the data to make it look more like the typical music player app?

Some useful information:
I downsample to single channel, 32kHz, and specify a time window of 35ms. That means the FFT gets ~1100 points. I vary these values to experiment (ie tried 16kHz, and increasing/decreasing interval length) but I get similar results.

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1 Answer

  1. Editorial Team

    With an FFT of 1100 points, you probably aren’t able to capture the low frequencies with a lot of frequency resolution.

    Think about it, 30 Hz corresponds to a period of 33ms, which at 32kHz is roughly 1000 samples. So you’ll only be able to capture about 1 period in this time.

    Thus, you’ll need a longer FFT window to capture those low frequencies with sharp frequency resolution.

    You’ll likely need a time window of 4000 samples or more to start getting noticeably more frequency resolution at the low frequencies. This will be fine too, since you’ll still get about 8-10 spectrum updates per second.

    One option too, if you want very fast updates for the high frequency bins but good frequency resolution at the low frequencies, is to update the high frequency bins more quickly (such as with the windows you’re currently using) but compute the low frequency bins less often (and with larger windows necessary for the good freq. resolution.)

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