Which sampling rates you can use depend on your sound card, some sound cards can go down to 8 kHz and even 4 kHz. WinMLS gives an error message when you start a measurement if the selected sampling frequency is not supported.
Our experience is that the best results are obtained if the upper sweep frequency is set to Max as shown in the figure above. At least you should follow this: WE RECOMMEND THAT YOU SET THE LOWER FREQUENCY SOMEWHAT LOWER THAN THE LOWEST FREQUENCY YOU WISH TO MEASURE. For example, you with to measure down to 20 Hz. Then you should start the sweep at 16 Hz as shown in the figure above.
If the upper frequency is much lower than the Nyquist frequency (Fs/2), resampling is used to reduce the file size. This means that after the measurement is performed, the measurement is processed so that the high frequencies above the selected upper frequency are removed.
Note: The result of the resampling process depends on the measurement settings. You should first perform a loopback measurement of the sound card to check the result. If it has ripple in the frequency response that is too high for your application, increase the measurement duration and try again. Best results have been reported if you select the settings in step no. 6 as shown below