I decided to change cable organizations and arrangements of PC and desk. There were many points I was dissatisfied with. For example, the display was on the right of the desk, but I preferred more left on the center of the desk. I did change the arrangement. I was satisfied with the new arrangement. The pc speaker, however, did not sound suddenly. I didn't know new arrangement cause that or not. I checked the config of the speaker and looked for the reason. Finally, I suspected using an unexpected sound driver was the reason. I uninstalled it, and my pc speaker sounded.
