Sounds as vehicles/guns anf facilities

[mongoose]

After seeing an earlier post WRT spawn sounds, I thought i would look at the MAW 'siren' and see what's up. Now in MAW, it's not anywhere as a facility in its own right, but part or airfields or whatever. So I decided to make a facility of just the siren which was like this

<Facility Type="siren" Flags="isMilitary" OuterDistance="20000">
<Units>
<Unit Type="siren" Position="0.00 0.00" Angle="0.00"/>
</Units>
<GroundPlanes/>
<Routes/>
</Facility>

I checked it out both in MAW and my ETO (with relevant MAW files added} in test missions where I just had a German aircraft flying over several of the siren.xml facility at different heights. I turned off the engine sound as well just in case it masked the siren. However I heard nothing in either MAW or ETO.

Now I checked test missions with a couple of other facilities such as 105mm_star_shell (nothing!} and tow_searchlight_1, which showed up fine.

If I had just checked with ETO and not MAW, I could have thought I made an error in copying files but with no sound effect in MAW, I am wondering what goes with sound files? I am assuming one doesn't have to make spawn files if one can place facilities (taht work!!) in missions?

EDIT: I dikdn't mess with the sounds.xml which maybe I should have! How I'm not sure though.
Any ideas as I already have made sound wav files for a knickebein and x-gerat! ... and --- and -.-.-.