Streaming music sounds better late at night. Is this just me?

According to FCC website:

“Most AM radio stations are required by the FCC’s rules to reduce their power or cease operating at night in order to avoid interference to other AM stations.  FCC rules governing the daytime and nighttime operation of AM radio stations are a consequence of the laws of physics.  Because of the way in which the relatively long wavelengths of AM radio signals interact with the ionized layers of the ionosphere miles above the earth’s surface, the propagation of AM radio waves changes drastically from daytime to nighttime.  This change in AM radio propagation occurs at sunset due to radical shifts in the ionospheric layers, which persist throughout the night.”

@chungjh   Reducing transmitting power reduces pollution from electromagnetic waves as well as pollution of the grid by radio stations.  

We had few discussions on this subject and so far nobody has been able to pinpoint the reason for improved sound at night.  I suspect that all factors play small role, including electrical grid pollution, reduced AM waves, reduced cellphone traffic etc.  
There will be some noise injected from the Ethernet.  Ethernet has inherent isolation, but nothing is perfect (there are always few pF across).  Perhaps some ethernet filtering might help, but I don't know much about it.  Other than that, usual precautions, like running signal and speaker cables away from (or perpendicular to) power cables, proper grounding and shielding etc.