I was watching streamed video on the computer when the sound went off. There was no sound output on either the external speakers or the internal speaker. I contacted Microsoft via their support webpage and reported this. The sound output returned to operating condition.
After a few days the sound output again went off on the external speakers but continued on the internal one. I now have to watch streamed video on the TV to get adequate sound quality on Youtube videos. The computer is a HP Elite 8200