我遇到了一个声音问题，声音设置显示为“虚拟输出”，这意味着它无法读取我的音频卡。
我按照这里的指示进行操作，采用了“备选”方法，运行了“sudo apt-get remove --purge alsa-base pulseaudio”，但是“sudo apt-get install alsa-base pulseaudio”给我显示了以下内容：
我连声音图标都没有。我该如何安装这两个软件包？
我按照这里的指示进行操作，采用了“备选”方法，运行了“sudo apt-get remove --purge alsa-base pulseaudio”，但是“sudo apt-get install alsa-base pulseaudio”给我显示了以下内容：
Reading package lists... Done
Building dependency tree
Reading state information... Done
Package pulseaudio is not available, but is referred to by another package.
This may mean that the package is missing, has been obsoleted, or
is only available from another source
Package alsa-base is not available, but is referred to by another package.
This may mean that the package is missing, has been obsoleted, or
is only available from another source
E: Package 'alsa-base' has no installation candidate
E: Package 'pulseaudio' has no installation candidate
我连声音图标都没有。我该如何安装这两个软件包？