Fmod distance parameter

Is there a way to only set the distance parameter in Fmod for iPhone development? I can set 3D Max och Min Distance in Fmod Designer. I would like to only use the distance feature and not the angle feature in Fmod.

In the following code I add the position of the listener to the sound, but I want to just add the distance between the listener and the sound:

    listenerpos.y = (float)33.0f * DISTANCEFACTOR;
    result = system->set3DListenerAttribut开发者_Go百科es(0, &listenerpos, &vel, &forward, &up);

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If you don't want to update any particular parameter for System::set3DListenerAttributes, simply pass in 0 or NULL.

system->set3DListenerAttributes(0, &listenerpos, NULL, NULL, NULL);