解決方法：https://forum.manjaro.org/t/no-sound-solved/3517
LOL i feel like such a noob. Fixed my problem after searching these forums and found this thread. Manjaro menu>Multimedia>PulseAudio Volume Control then once in "Volume Control" went to "Configuration" and switched the profile to "Analog Stereo Duplex" Problem solved.
在配置里把第一個Built-in Audio 改成了off,把第二個Built-in Audio 改成了Analog Stereo Duplex。
2017-12-26,今天在manjaro滾動更新之后，再次遇到了沒有聲音的問題。最后還是在"Volume Control" 中的第二個Built-in Audio解決的，不過這次是改成了Analog Stereo Output.完全不明白背后的原因。