<P>This initial covered area is small enough for the outdoor PrecipitationZone rain and sound to cover.
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<P>The stairway down contains a PrecipitationShelter zone, which activates PrecipitationNodes above the entry stairways.  It also activates a pair of ShelterSounds at the top of the lower stairway, so that we leave the rain sound behind as we descend the stairs.
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<P>At the bottom of the stairs is another PrecipitationShelter zone. It extends to the mouth of the far stairway back to the surface, which has its own PrecipitationNodes and ShelterSounds.
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<P>Entering the lower zone disables the PrecipitationNodes over the stairs on this end, but in this example these two shelter zones actually share the same ShelterSounds, so the sounds on this end do not turn off when entering the lower zone.
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<P>It isn't strictly necessary to have two shelter zones here, but setting it up this way reduces the number of PrecipitationNodes that are active at the same time.