お使いのノートPCIあるいはマザーボードの情報も投稿していただくと、同じようなものを使っている人からの回答を得られるかもしれません。

デバイスの詳細な情報を知りたいので、以下の2つのコマンドの出力を教えてください。2つ目のコマンドは長々と出力されますので、驚かないでください。

$ lspci -vnns 00:1b.0
$ cat /proc/asound/card0/codec#*

yasuyoshi69 による投稿:

昨日くらいから色々、いじったせい？で、 cat /proc/asound/cardsを実行しても

NO　SOUNDCARDSと出ますし、

Oh... これはサウンドデバイスドライバを有効にできていないことを意味します。元の状態に戻すことをオススメします。。。

うーん、この状態になるということは、パスワード入力を求められるような操作=システムに変更を加えるような操作を行っているはずです。まずは何をしたか思い出すところから始めるのがよいように思います。

mocchi様、ありがとうございます。

~$ lspci -vnns 00:1b.0を実行したら、

00:1b.0 Audio device [0403]: Intel Corporation NM10/ICH7 Family High Definition Audio Controller [8086:27d8] (rev 02)
    Subsystem: Sony Corporation Device [104d:8205]
    Flags: bus master, fast devsel, latency 0, IRQ 44
    Memory at dc1c0000 (64-bit, non-prefetchable) [size=16K]
    Capabilities: <access denied>
    Kernel driver in use: snd_hda_intel
    Kernel modules: snd-hda-intel

と出て、

~$ cat /proc/asound/card0/codec#*を実行したら、

Codec: SigmaTel CXD9872RD/K
Address: 0
AFG Function Id: 0x1 (unsol 1)
Vendor Id: 0x83847661
Subsystem Id: 0x104d1200
Revision Id: 0x104201
No Modem Function Group found
Default PCM:
    rates [0x7e0]: 44100 48000 88200 96000 176400 192000
    bits [0xe]: 16 20 24
    formats [0x1]: PCM
Default Amp-In caps: ofs=0x00, nsteps=0x0f, stepsize=0x05, mute=1
Default Amp-Out caps: ofs=0x7f, nsteps=0x7f, stepsize=0x02, mute=1
GPIO: io=5, o=0, i=0, unsolicited=1, wake=1
  IO[0]: enable=0, dir=0, wake=0, sticky=0, data=0, unsol=0
  IO[1]: enable=0, dir=0, wake=0, sticky=0, data=0, unsol=0
  IO[2]: enable=0, dir=0, wake=0, sticky=0, data=0, unsol=0
  IO[3]: enable=0, dir=0, wake=0, sticky=0, data=0, unsol=0
  IO[4]: enable=0, dir=0, wake=0, sticky=0, data=0, unsol=0
Node 0x02 [Audio Output] wcaps 0xd0c05: Stereo Amp-Out R/L
  Control: name="Headphone Playback Volume", index=0, device=0
    ControlAmp: chs=3, dir=Out, idx=0, ofs=63
  Control: name="Headphone Playback Switch", index=0, device=0
    ControlAmp: chs=3, dir=Out, idx=0, ofs=0
  Amp-Out caps: N/A
  Amp-Out vals:  [0x7f 0x7f]
  Converter: stream=8, channel=0
  Power: setting=D0, actual=D0
  Delay: 13 samples
Node 0x03 [Audio Output] wcaps 0xd0c05: Stereo Amp-Out R/L
  Amp-Out caps: N/A
  Amp-Out vals:  [0xff 0xff]
  Converter: stream=0, channel=0
  Power: setting=D0, actual=D0
  Delay: 13 samples
Node 0x04 [Audio Output] wcaps 0xd0c05: Stereo Amp-Out R/L
  Amp-Out caps: N/A
  Amp-Out vals:  [0xff 0xff]
  Converter: stream=0, channel=0
  Power: setting=D0, actual=D0
  Delay: 13 samples
Node 0x05 [Audio Output] wcaps 0xd0c05: Stereo Amp-Out R/L
  Control: name="Speaker Playback Volume", index=0, device=0
    ControlAmp: chs=3, dir=Out, idx=0, ofs=63
  Control: name="Speaker Playback Switch", index=0, device=0
    ControlAmp: chs=3, dir=Out, idx=0, ofs=0
  Device: name="STAC92xx Analog", type="Audio", device=0
  Amp-Out caps: N/A
  Amp-Out vals:  [0x7f 0x7f]
  Converter: stream=8, channel=0
  Power: setting=D0, actual=D0
  Delay: 13 samples
Node 0x06 [Audio Input] wcaps 0x1d0541: Stereo
  Converter: stream=0, channel=0
  SDI-Select: 0
  Power: setting=D0, actual=D0
  Delay: 13 samples
  Connection: 1
     0x07
  Processing caps: benign=0, ncoeff=0
Node 0x07 [Audio Selector] wcaps 0x300903: Stereo Amp-In R/L
  Amp-In caps: N/A
  Amp-In vals:  [0x80 0x80]
  Connection: 1
     0x0e
Node 0x08 [Audio Input] wcaps 0x1d0541: Stereo
  Device: name="STAC92xx Analog", type="Audio", device=0
  Converter: stream=4, channel=0
  SDI-Select: 0
  Power: setting=D0, actual=D0
  Delay: 13 samples
  Connection: 1
     0x09
  Processing caps: benign=0, ncoeff=0
Node 0x09 [Audio Selector] wcaps 0x300903: Stereo Amp-In R/L
  Control: name="Capture Volume", index=0, device=0
    ControlAmp: chs=3, dir=In, idx=0, ofs=0
  Control: name="Capture Switch", index=0, device=0
    ControlAmp: chs=3, dir=In, idx=0, ofs=0
  Amp-In caps: N/A
  Amp-In vals:  [0x0f 0x0f]
  Connection: 1
     0x15
Node 0x0a [Pin Complex] wcaps 0x400181: Stereo
  Control: name="Headphone Jack", index=0, device=0
  Pincap 0x0000173c: IN OUT HP Detect
    Vref caps: HIZ 50 GRD 80
  Pin Default 0x012110f0: [Jack] HP Out at Ext Rear
    Conn = 1/8, Color = Black
    DefAssociation = 0xf, Sequence = 0x0
  Pin-ctls: 0xc0: OUT HP VREF_HIZ
  Unsolicited: tag=01, enabled=1
  Connection: 1
     0x02
Node 0x0b [Pin Complex] wcaps 0x400181: Stereo
  Pincap 0x00000014: OUT Detect
  Pin Default 0x40f000fb: [N/A] Other at Ext N/A
    Conn = Unknown, Color = Unknown
    DefAssociation = 0xf, Sequence = 0xb
  Pin-ctls: 0x00:
  Unsolicited: tag=00, enabled=0
  Connection: 1
     0x04
Node 0x0c [Pin Complex] wcaps 0x400181: Stereo
  Pincap 0x00000014: OUT Detect
  Pin Default 0x40f000fc: [N/A] Other at Ext N/A
    Conn = Unknown, Color = Unknown
    DefAssociation = 0xf, Sequence = 0xc
  Pin-ctls: 0x00:
  Unsolicited: tag=00, enabled=0
  Connection: 1
     0x03
Node 0x0d [Pin Complex] wcaps 0x400181: Stereo
  Control: name="Mic Jack Mode", index=0, device=0
    ControlAmp: chs=0, dir=In, idx=0, ofs=0
  Control: name="Mic Jack", index=0, device=0
  Pincap 0x0000173c: IN OUT HP Detect
    Vref caps: HIZ 50 GRD 80
  Pin Default 0x01a1502e: [Jack] Mic at Ext Rear
    Conn = 1/8, Color = Red
    DefAssociation = 0x2, Sequence = 0xe
  Pin-ctls: 0x24: IN VREF_80
  Unsolicited: tag=02, enabled=1
  Connection: 1
     0x02
Node 0x0e [Pin Complex] wcaps 0x400081: Stereo
  Pincap 0x00000024: IN Detect
  Pin Default 0x90811050: [Fixed] Line In at Int N/A
    Conn = 1/8, Color = Black
    DefAssociation = 0x5, Sequence = 0x0
  Pin-ctls: 0x20: IN
  Unsolicited: tag=00, enabled=0
Node 0x0f [Pin Complex] wcaps 0x400181: Stereo
  Pincap 0x00000014: OUT Detect
  Pin Default 0x90170010: [Fixed] Speaker at Int N/A
    Conn = Analog, Color = Unknown
    DefAssociation = 0x1, Sequence = 0x0
  Pin-ctls: 0x40: OUT
  Unsolicited: tag=00, enabled=0
  Connection: 1
     0x05
Node 0x10 [Audio Output] wcaps 0x40211: Stereo Digital
  Converter: stream=0, channel=0
  Digital:
  Digital category: 0x0
  PCM:
    rates [0x3e0]: 44100 48000 88200 96000 176400
    bits [0xe]: 16 20 24
    formats [0x5]: PCM AC3
  Delay: 4 samples
Node 0x11 [Pin Complex] wcaps 0x400301: Stereo Digital
  Pincap 0x00000010: OUT
  Pin Default 0x40f000fd: [N/A] Other at Ext N/A
    Conn = Unknown, Color = Unknown
    DefAssociation = 0xf, Sequence = 0xd
  Pin-ctls: 0x00:
  Connection: 2
     0x10* 0x09
Node 0x12 [Audio Input] wcaps 0x140311: Stereo Digital
  Converter: stream=0, channel=0
  SDI-Select: 0
  Digital:
  Digital category: 0x0
  PCM:
    rates [0x160]: 44100 48000 96000
    bits [0xe]: 16 20 24
    formats [0x5]: PCM AC3
  Delay: 4 samples
  Connection: 1
     0x13
Node 0x13 [Pin Complex] wcaps 0x440381: Stereo Digital
  Pincap 0x00000034: IN OUT Detect
  Pin Default 0x40f000fe: [N/A] Other at Ext N/A
    Conn = Unknown, Color = Unknown
    DefAssociation = 0xf, Sequence = 0xe
  Pin-ctls: 0x00:
  Unsolicited: tag=00, enabled=0
  Delay: 4 samples
  Connection: 1
     0x18
Node 0x14 [Pin Complex] wcaps 0x400001: Stereo
  Pincap 0x00000020: IN
  Pin Default 0x90a70021: [Fixed] Mic at Int N/A
    Conn = Analog, Color = Unknown
    DefAssociation = 0x2, Sequence = 0x1
  Pin-ctls: 0x20: IN
Node 0x15 [Audio Selector] wcaps 0x30010d: Stereo Amp-Out
  Control: name="Mux Capture Volume", index=0, device=0
    ControlAmp: chs=3, dir=Out, idx=0, ofs=0
  Amp-Out caps: ofs=0x00, nsteps=0x04, stepsize=0x27, mute=1
  Amp-Out vals:  [0x00 0x00]
  Connection: 4
     0x0a 0x0d 0x14* 0x02
Node 0x16 [Beep Generator Widget] wcaps 0x70000c: Mono Amp-Out
  Amp-Out caps: ofs=0x03, nsteps=0x03, stepsize=0x17, mute=0
  Amp-Out vals:  [0x00]
Node 0x17 [Volume Knob Widget] wcaps 0x600000: Mono
  Volume-Knob: delta=1, steps=127, direct=0, val=127
  Connection: 4
     0x02 0x03 0x04 0x05
Node 0x18 [Audio Output] wcaps 0x40201: Stereo Digital
  Converter: stream=0, channel=0
  Digital:
  Digital category: 0x0
  Delay: 4 samples
Codec: Conexant ID 2bfa
Address: 1
MFG Function Id: 0x2 (unsol 1)
Vendor Id: 0x14f12bfa
Subsystem Id: 0x104d0200
Revision Id: 0x90000
Modem Function Group: 0x2

と出ました。

申し訳ありませんが、ご教示お願い致します。