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 dialog 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. You can download the recordings here and load them into Overtone Analyzer yourself:
Tuning Fork tuned to 105Hz sampled at 11025Hz
Tuning Fork tuned to 105Hz sampled at 44100Hz
| Sampling Rate: 11025Hz | Sampling Rate: 44100Hz |
|---|---|
FFT Size: 512 Points |
|
Frequency Resolution: 21.5Hz |
Resolution: 86.1Hz |
| FFT Size: 1024 Points | |
Resolution: 10.8Hz |
Resolution: 43.1Hz |
| FFT Size: 2048 Points |
|
Resolution: 5.4Hz |
Resolution: 21.5Hz |
| FFT Size: 4096 Points |
|
Resolution: 2.7Hz |
Resolution: 10.8Hz |
| FFT Size: 8192 Points |
|
Resolution: 1.3Hz |
Resolution: 5.4Hz |
| FFT Size: 16384 Points |
|
Resolution: 0.7Hz |
Resolution: 2.7Hz |
| Sampling Rate: 11025Hz | Sampling Rate: 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.
