My Lenovo P620 uses Realtek ALC4050H USB 2.0 audio codec and it's power state mappings are causing audio drop outs after ten seconds of idle sound. It's quite annoying... truncated sounds and a slight pop noise when it powers down. If I switch the driver to the Microsoft USB Audio 2.0 driver, the problem goes away. Unfortunately, the Realtek software doesn't work correctly when using the Windows USB Audio driver.
In this screenshot, the left image is using the Windows USB Audio driver and the right image is the Realtek driver. The Windows driver power state mappings are either D0 or D3. The Realtek uses D2 for every power state except D0 or D5, thus causing the audio port to go into a sleep mode after 10 seconds... causing a popping sound and truncated audio when the power state jumps from D2 to D0.
I'm not familiar with modifying drivers, I think this problem could be fixed quite easily by modifying the Realtek drivers power state mappings.