Hi.

Some commands and responses :-

% cat /etc/asound.conf
pcm.!default {
type hw
card 0
}

ctl.!default {
type hw
card 1
}

% aplay --list-devices
**** List of PLAYBACK Hardware Devices ****
card 0: PCH [HDA Intel PCH], device 0: ALC887-VD Analog [ALC887-VD Analog]
Subdevices: 0/1
Subdevice #0: subdevice #0
card 0: PCH [HDA Intel PCH], device 1: ALC887-VD Digital [ALC887-VD Digital]
Subdevices: 1/1
Subdevice #0: subdevice #0
card 1: NVidia [HDA NVidia], device 3: HDMI 0 [HDMI 0]
Subdevices: 1/1
Subdevice #0: subdevice #0
card 1: NVidia [HDA NVidia], device 7: HDMI 1 [HDMI 1]
Subdevices: 1/1
Subdevice #0: subdevice #0

% cat /proc/asound/cards
0 [PCH ]: HDA-Intel - HDA Intel PCH
HDA Intel PCH at 0xf7210000 irq 45
1 [NVidia ]: HDA-Intel - HDA NVidia
HDA NVidia at 0xf7080000 irq 17

Am I right in thinking that the contents of /etc/asound.conf
indicate that pulseaudio is not being used, but ALSA alone
is used for the sound ?

Audio output is to a pair of speakers connected to the PC
via the normal headphone output from the PC.

Hence as I understand it, sound should be produced by card 0.

In addition, the YouTube sound has now suddenly re-appeared
without any obvious reason. This indicates a pattern of sound
suddenly disappearing without obvious reason and then suddenly
re-appearing days or perhaps weeks later. Could this problem
be due to certain programs suddenly stopping or restarting the sound ?

Regards,

Mike Bailey

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27. Oct 2017 15:25 by pg_oxl@oxl.for.sabi.co.uk:

I have a problem with no sound when using Iceweasel on a
Debian Jessie system. [ ... ]

That is a bit generic: is sound otherwise available to
applications? If a page has background audio can that be heard?
Later you mention the Flash plugin, but a lot of sound comes
with HTML5 pages nowadays, and the sound is not routed via the
Flash plugin.
pcm.pulse {type pulse}ctl.pulse {type pulse}pcm.!default {type pulse}

That might be instead (and just in '/etc/asound.conf'):

------------------------------------------------------------------------
pcm.pulse { type pulse; }
ctl.pulse { type pulse; }

pcm.!default { type pulse; fallback "sysdefault"; }
ctl.!default { type pulse; fallback "sysdefault"; }
------------------------------------------------------------------------

But something like that should be the default...

Usually to sort out sound issues it is necessary to start bottom
up, first checking that the ALSA layer works (which includes
checking that the default sound device is right and unmuted),
then that PulseAudio layer works (which includes checking that
the right ALSA device is the default, and it is unmuted), and
then the application layer.

For ALSA there is a troubleshooting list here:

http://www.sabi.co.uk/Notes/linuxSoundALSA.html#troubles

For PulseAudio the best first approach is the GUI program
'pavucontrol' that allows checking that the appo output device
selected is the right one (sometimes the default is "Null
Output" or the sound card built into most HDMI GPUs), and that
sound does get through (connection appears in "Playback" tab).