If you have recently installed Arch Linux you may have found that there is no sound when playing media. This is because by default ALSA has all channels muted.
Installing the ALSA Utilities
The Advanced Linux Sound Architecture (ALSA) is the part of the Linux kernel that manages the sound devices on your system. In addition to this the project also provides several command-line utilities that allow you to configure these devices. These can be installed with pacman.
$ sudo pacman -S alsa-utils
Unmuting The Channels
Channels can be unmuted with amixer.
$ amixer sset Master unmute $ amixer sset Speaker unmute $ amixer sset Headphone unmute
You can test that the speakers are working with the speaker-test command.
$ speaker-test -c 2
If you are still getting no sound then it could be that the volume has been set to zero. Use amixer again to increase the volume.
$ amixer sset Master 100% $ amixer sset Speaker 100% $ amixer sset Headphone 100%
Unmute with Alsamixer
If you prefer a more intuitive ncurses interface you can use alsamixer.
Channels that are muted will have the MM label below them. Unmuted channels have 00.
Use the ← and → keys to scroll to the muted channel and press m to unmute it.
The volume can be increased and decreased with the ↑ and ↓ keys.