Virtual sound card has a little noise

[frank9306]

I installed the virtual machine sound card in the virtual machine equipped with windows7 system, and used the IVSHMEM to conduct sound test. Everything was normal, but occasionally there was a little noise.This is a real headache. I wonder what all about. Thank you so much.

[Qwerty-Space]

Is it crackling/popping noises?

[WXZhao7]

I try to find the source of the noise. Finally, I recognized the noise coming from the motherboard. The background noise is stable and not relative to the volume. When nothing input, the ALSA turns hardware output off, and the background noise disappears. Any input with volume equals 0 will turn hardware output on, and the electronic background noise appears.
Here I recorded the output of ALSA with two cases. Case 1: scream or any input with volume equals 0. Case 2: no input and only recording. In case2, the noises only appeared when the recording existed.