Sampling Rate and Frequency Resolution

Higher sampling rates are not automatically better, because a higher sampling rate means lower frequency resolution for the same FFT size. To understand what that means, open the Analyzer Settings page and experiment with changing the sampling rate from 11025Hz to 96000Hz. Notice how the frequency resolution decreases as the sampling rate increases.

If the sampling rate is doubled, the FFT Size also needs to be doubled to get the same frequency resolution. Therefore, set the sampling rate as high as necessary for the highest frequency that you want to measure, but not higher. If you want to measure very low frequencies (100Hz or lower), lowering the sampling rate will increase the accuracy of the measurement without requiring a larger FFT Size.

The table below shows the spectrum of a tuning fork that is tuned to 105Hz at various FFT Sizes to compare the analyzer accuracy at sampling rates of 11025Hz and of 44100Hz.

In this example, the frequency scale range is 75Hz to 135Hz, and the dynamic range is 66dB, starting at -8dB. The time resolution was set to 1 update per second.

For a broader overview of how sampling rate, FFT size, and frequency resolution interact, with a table that extends to 2²⁰ FFT bins and notes on real-world microphone bandwidth limits, see the high-resolution audio spectrum analyzer page.