The problem is related to PulseAudio. When I remove it, the sound is OK. In volume control applet and paman, this problem looks like Flightgear keeps disconnecting and reconnecting to sound server.
The problem is related to PulseAudio. When I remove it, the sound is OK. In volume control applet and paman, this problem looks like Flightgear keeps disconnecting and reconnecting to sound server.