SoListenerGainElement(3) on Linux
The text e6d6cc0e2fb1, as Debian 6.0 (Squeeze) shipped it.
The SoListenerGainElement class stores the SoListener gain during a scene graph traversal. This gain is set by SoListener nodes during audio rendering. The SoListenerGainElement is used when the SoVRMLSound nodes render themselves.