no, in my instance it is not related to USB at all. These pulses are present with any gain and their pattern depends on LO frequency value. It doesn't depends on sample rate. I also tested with clean external low-noise lab power supply and ferrite beads to make sure that there is no issue with power supply. Tested it with RFI filters on USB cable. Nothing of my attempts doesn't affect that "pulse sound" issue at all. Also I tested it on different PC and notebook. There is no even a little correlation with power supply, USB noise or PC.
RTLSDRv3 at the same USB port doesn't have such sound pulses and crackles at all. I even tried to connect both MSI.SDR and RTLSDRv3 to the same antenna and used them simultaneously. Both devices shows the same sensitivity, but there is no pulses on RTLSDRv3 and these pulses are present on MSI.SDR.
I also found that when you change LO, spurs are moving across bandwidth and at some frequencies they are merged together. Near these frequencies, these random pulses appears across entire waterfall and going to very loud. Also I tested EMI/RFI with RTLSDRv3 around this MSI.SDR pcb and there is no such pulses in reality. It happens inside chip due to some defect. So, this is definitely hardware defect.
Also, my MSI.SDR cannot work stable at 10 MHz sample rate. When I switch to 10 MHz, noise floor starts to jumping like crazy and all what I hear is just terrible noise, random oscillations, pulses and crackles
Also, I found that sometimes with 600 kHz filter and 2 MHz sample rate, sound periodically disappears and appears again. For example it plays sound for 2-3 seconds and then sound stops for a second and then playing again. It doesn't related with PC hardware, because there is powerful i5 processor working at 2800 MHz and CPU load is smaller than 5%.
Also I found that crystal oscillator in MSI.SDR has very high phase noise. It leads to high "Batman ears" effect around clean sine source on the spectrum. These "batman ears" is just 45 dBc. While RTLSDRv3 can show it with about 80 dBс noise floor around the signal.
And also I found that my MSI.SDR has very high IMD distortions, it is much worse than RTLSDRv3. I connected both devices together, and MSI.SDR has distortions and curvature noise floor around power signals (45 dB above noise floor), where RTLSDR shows it with no distortions and with flat noise floor. I tried to connect MSI.SDR through bandpass filter which cuts just a very narrow piece of spectrum. But these IMD distortions are still present.
I'm very disappointed, MSI.SDR that I got works much-much worse than RTLSDRv3 (which costs just 21 USD).
Probably these MSI.SDR are attempt to sell factory rejected chips which is rejected from RSP manufacturing due to some defects. I'm just interesting, if other MSI.SDR also has such defects? Or it's just a random defect in my instance.
Another assumption is that these MSI.SDR using fake Mirics chipsets (cloned). And this may be the reason why my instance have such defects. I think in such case all these MSI.SDR will have such defects. Unfortunately a lot of people is not familiar with SDR technology and will just don't understand why it works so bad. So, if you have such defects, you should know that this is critical defect. Normal SDR receiver should not have random pulses all around full bandwidth.
Here two pictures taken in a row, they shows what sound pulses I'm talking about.
They randomly flashing all around full bandwidth (input RF connector is open):