我在 imac 上安装了 Ubuntu 16.04.1 LTS，但是声音不起作用。我的系统信息如下：
lsb_release -a：
No LSB modules are available.
Distributor ID: Ubuntu
Description: Ubuntu 16.04.1 LTS
Release: 16.04
Codename: xenial
lspci | grep Audio：
00:03.0 Audio device: Intel Corporation Broadwell-U Audio Controller (rev 09)
00:1b.0 Audio device: Intel Corporation Wildcat Point-LP High Definition Audio Controller (rev 03)
grep "Codec:" /proc/asound/card*/codec*：
/proc/asound/card0/codec#0:Codec: Intel Broadwell HDMI
/proc/asound/card1/codec#0:Codec: Cirrus Logic CS4208
lsmod | grep snd：
snd_hda_codec_hdmi 53248 1
snd_hda_codec_cirrus 20480 1
snd_hda_codec_generic 77824 1 snd_hda_codec_cirrus
snd_hda_intel 40960 10
snd_hda_codec 135168 4 snd_hda_codec_hdmi,snd_hda_codec_generic,snd_hda_intel,snd_hda_codec_cirrus
snd_hda_core 73728 5 snd_hda_codec_hdmi,snd_hda_codec_generic,snd_hda_codec,snd_hda_intel,snd_hda_codec_cirrus
snd_hwdep 16384 1 snd_hda_codec
snd_pcm 106496 7 snd_hda_codec_hdmi,snd_hda_codec,snd_hda_intel,snd_hda_core
snd_seq_midi 16384 0
snd_seq_midi_event 16384 1 snd_seq_midi
snd_rawmidi 32768 1 snd_seq_midi
snd_seq 69632 2 snd_seq_midi_event,snd_seq_midi
snd_seq_device 16384 3 snd_seq,snd_rawmidi,snd_seq_midi
snd_timer 32768 2 snd_pcm,snd_seq
snd 81920 28 snd_hwdep,snd_timer,snd_hda_codec_hdmi,snd_pcm,snd_seq,snd_rawmidi,snd_hda_codec_generic,snd_hda_codec,snd_hda_intel,snd_seq_device,snd_hda_codec_cirrus
soundcore 16384 1 snd
aplay -l：
**** List of PLAYBACK Hardware Devices ****
card 0: HDMI [HDA Intel HDMI], device 3: HDMI 0 [HDMI 0]
Subdevices: 0/1
Subdevice #0: subdevice #0
card 0: HDMI [HDA Intel HDMI], device 7: HDMI 1 [HDMI 1]
Subdevices: 1/1
Subdevice #0: subdevice #0
card 0: HDMI [HDA Intel HDMI], device 8: HDMI 2 [HDMI 2]
Subdevices: 1/1
Subdevice #0: subdevice #0
card 1: PCH [HDA Intel PCH], device 0: CS4208 Analog [CS4208 Analog]