Since the update thread is now closed, I’ll post my findings here.
I have posted under Software & Applications as this relates to a side effect of Virtualbox.
After the 28th April update, I noticed terrible, distorted audio on guest (Windows 10) and host after the latest virtualbox updates (6.1.20) were applied.
I discovered that Bluetooth audio (via the PulseAudio volume control) was not affected.
Next, I tried changing the host audio driver to ALSA (see image below), and then all was fine on the guest and host.
Perhaps someone will find this useful.
3 Likes
Same issue here. I tried on a few different guests and they all had same issue. In my case host system audio was sometimes distorted and sometimes delayed 3 or 5 seconds.
Reverting to version 6.1.18 solved the issue for now.
Did you try ALSA host audio driver before downgrading?
I tried again with a CentOS guest with Pulse Audio, and the sound was distorted in the host. After switching to ALSA driver, the sound was clear again.
Switching to ALSA did help. Thanks.
Just listing another solution 
Alternatives are great and help others who prefer to tinker in different ways. 