Sony Bravia KDL-46X2000 Operating Instructions Manual page 28

Dual Sound
Tip
Sound menu options other than "Dual Sound" cannot be used for headphones and audio output sockets.
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Selects the sound from the speaker for a stereo or bilingual broadcast.
"Stereo", "Mono": For a stereo broadcast.
"A"/"B"/"Mono": For a bilingual broadcast, select "A" for sound channel 1, "B" for
sound channel 2, or "Mono" for a mono channel, if available.
Tip
If you select other equipment connected to the TV, set "Dual Sound" to "Stereo", "A" or "B".