Alt-A synchron to sound

If I play a blendersecene with alt-a, is the sound and the motion asynchron. Very bad for lipsyn… :X
How can I get a good preview without rendering?

how is it not synched?

if it plays smoothly, but is off by a consistent amount of time something on your system is delaying the sound [and blender has no means to delay the video to match]

if it doesn’t play smoothly, I’d think you’d need to press the sync button [in the sound buttons, same place as render buttons], but iirc without it pressed you wouldn’t hear sound.