Since you didn't do anything to fix it, the intermittent loss of sound will probably continue. Others have reported the same thing, but it's not a widespread issue that affects everyone. It seems to occur more frequently on cable news channels. This could be an indication those channels require a stronger signal. The reason it resumes in the morning is probably because when sound is lost, an event such as a reboot or refresh is necessary to reinstate it. If you've never changed audio settings, you probably have a device or cable that's failing. At a minimum, disconnect the HDMI or audio cable, clean the port and reconnect. You might need to replace the cable.