Trouble again with PulseAudio and Thunderbird sound notifications

In an earlier post I described how I fixed a scratchy-sounding sound file which the Thunderbird e-mail client plays when a new message arrives. Well, the problem started again recently, but this time the contents of /etc/pulse/daemon.conf looked OK to me. Furthermore, the sound file sounds fine when played using following commands:

aplay ~/Music/wav/E-mail_notifications/halmsg.wav
paplay ~/Music/wav/E-mail_notifications/halmsg.wav
mplayer ~/Music/wav/E-mail_notifications/halmsg.wav
cvlc ~/Music/wav/E-mail_notifications/halmsg.wav

Now, Thunderbird uses libcanberra to play sounds, so I began to wonder if the problem lay with libcanberra. As it happens, libcanberra is maintained by the same person who invented PulseAudio. However, I notice from the libcanberra Git repository that its source code has not been changed since 2012.

My Gentoo Linux installation had libcanberra installed with support for both ALSA and PulseAudio:

root # eix -I libcanberra
[I] media-libs/libcanberra
     Available versions:  0.30-r5 {alsa gnome gstreamer +gtk +gtk3 oss pulseaudio +sound tdb udev ABI_MIPS="n32 n64 o32" ABI_PPC="32 64" ABI_S390="32 64" ABI_X86="32 64 x32"}
     Installed versions:  0.30-r5(08:27:41 18/05/18)(alsa gtk gtk3 pulseaudio sound udev -gnome -gstreamer -oss -tdb ABI_MIPS="-n32 -n64 -o32" ABI_PPC="-32 -64" ABI_S390="-32 -64" ABI_X86="32 64 -x32")
     Homepage:            http://git.0pointer.net/libcanberra.git/
     Description:         Portable sound event library

So, even though my installation uses PulseAudio, I decided to try and re-install libcanberra without PulseAudio support, only ALSA support:

root # USE="-pulseaudio" emerge -1v libcanberra
root # eix -I libcanberra
[I] media-libs/libcanberra
     Available versions:  0.30-r5 {alsa gnome gstreamer +gtk +gtk3 oss pulseaudio +sound tdb udev ABI_MIPS="n32 n64 o32" ABI_PPC="32 64" ABI_S390="32 64" ABI_X86="32 64 x32"}
     Installed versions:  0.30-r5(15:47:14 26/05/18)(alsa gtk gtk3 sound udev -gnome -gstreamer -oss -pulseaudio -tdb ABI_MIPS="-n32 -n64 -o32" ABI_PPC="-32 -64" ABI_S390="-32 -64" ABI_X86="32 64 -x32")
     Homepage:            http://git.0pointer.net/libcanberra.git/
     Description:         Portable sound event library

Lo and behold, Thunderbird (libcanberra) plays the sound file correctly now. So I have added the following line to my file /etc/portage/package.use/thunderbird in order to make the change permanent:

media-libs/libcanberra -pulseaudio

PulseAudio 🙄