I played around with the sample rate settings and the ASIO buffer size of the sound card. Nothing depends on the sampling rate. Sweep's smallest Captured plot start delay is obtained if the ASIO buffer is 128 samples. If less, the delay increases, plus the sound card is unstable, it may turn off, or the SPL graph may have artifacts. If more, the delay increases. But in all cases the SPL and phase plots are the same.