Collision Sounds and small objects

I'm using this simple script to get some temporary physical opbjects to emit sounds during collisions

default
{
    on_rez(integer start_param)
    {llSetTimerEvent(10);//set up timer for die
}
state_entry()

{
    llCollisionSound("Boing", 1.0);
}

timer()
{llDie();//kills object after  timer
}
}

Ok so far so good. I've got a nice big object and when i drop it onto the floor it goes boing!

Now, if I reduce the size of this object to below around 0.5m per side the collision sound stops triggering.

Is this due to size, mass or what?

Any help would be great

Ok. So now the search offers up some help. Why won't it give the same results each time!

So CollisionSounds aparently only work with objects larger than 0.15m per side.

Help came from this thread

/54/98/31062/1.html

So now I must use LandCollision detection which is slower than CollisionSound.

Shame. Seems odd the Lindens would limit the effect of SoundCollision when so many small physical objects are intended to collide with things (bullets for instance).