Although somewhat indicative, you shouldn't take much stock in this measurement. If you are monitoring noise, the response is going to be bouncing all around and the response will vary several dB just depending on when you take a snapshot. Also, especially in low frequencies, you cannot use FFT to obtain a very objective measurement. FFT analysis is not logarithmic, and breaking 96kHz into 8192 frequency bins gives very little resolution in low frequency. FFT cannot completely isolate a single band, it uses a windowing function that is a compromise of selectivity and accuracy. It is a very in-depth topic I don't feel like writing a treatise on right now. I tried to discover information about how the FFT analysis is performed in the Voxengo CurveEQ software, but there was no documentation. The smoothing of the line means we don't see the bins or samples, so don't have enough information to draw much conclusion, especially since you are live-sampling noise. You've found the reason for nothing. +0.1dB is imperceptible. Only kids and bats can hear above 15kHz, and likely your PA speakers are down 10dB+ at the 20kHz frequency 'peak'. The frequency response curve is exceptional, a standard that other analog components would struggle to meet. The peak is probably a function of the order of lowpass filtering that can clearly be seen.