sudo apt-get install pavucontrol alsa-utils

Alsamixer F6 selects the sound card to see if it is muted

Use pavucontrol to see if there is output while playing the sound

aplay -l Check whether there is a sound device

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This problem has been encountered several times. The first time was when the HDMI cable was connected to the display. Later, after updating the kernel of Ubuntu, I encountered it again. I hereby record it.

When using HDMI, both video and sound will be output by default, and then the sound will go directly from the host computer to the monitor through the HDMI cable (it seems to output directly without using the sound card?), you can connect speakers or headphones, but the jack is at the back, so the operation is very difficult Trouble, generally still used to use the interface on the host. So the purpose is very clear, which is to separate the sound and go through the original channel

The steps are as follows :

1. Make sure the audio output is normal

Enter the terminal and set the audio output in alsa so that it is not muted

$ alsamixer

Find the item <S/PDIF 1>, some machines may be <S/PDIF>. If its value is 'MM', press m key to change it to '00', press Esc to exit

1. set output mode

Go to the 'Hardware' tab in the Ubuntu sound settings and set the configuration to 'Analog Stereo Duplex'. If all goes well, the sound will come out at this time

Reprinted in: https://my.oschina.net/Rosewillow/blog/676574