This is the sound that happens when the DAC is effectively "going to sleep" when no more data is being detected by the device. Because there are no drivers for MacOS (or Linux), there is no way to set the device to have the data streaming be always on. PC users have the luxury of setting it up that way in the audio control app that comes with the driver, so they don't have to deal with it so much. It is something that has been brought up with Topping several times, I think. It is also not something that is specific to this device, it will happen with most DACs that use the XMOS chip. As it has been mentioned, this only affects the USB input.
On MacOS (and I also suspect Linux), one workaround is to use a separate USB DDC (like a Topping D10s or the SMSL PO100 or PO100 Pro). That is how I have it set up with my desktop system. Alternatively, you can boot Qobuz, and leave it running in the background since it keeps sending a constant stream of data to the DAC, preventing it from going to sleep (or search the forum for the KeepMyMacAudioAlive for a user-built app that does the same thing).