Element Strengths

I've decided to greatly simplify the mechanics of my game Elemental Tiles.  Instead of having to figure out a bunch of different interactions that could happen like before, the goal now is to simply make the tiles disappear.  This happens by pushing different elements together that cause some kind of reaction.

There are now eight elements to play with:  Fire, Wood, Earth, Electric, Water, Metal, Air, and Sonic.  Every element is strong against one element and weak against another:  Earth is strong against Electric and weak against Wood, Metal is strong against Air and weak against Water, etc.  Also, each element has an opposite:  Fire's opposite is Water, Metal's opposite is Wood, etc.  You could think about the elements as being positioned on a wheel in the order listed above.  Elements directly across from each other are opposites and each one is stronger than the one directly to its right (or left I suppose, if you're in Australia).

When you push two tiles together, a reaction occurs if one is stronger than the other, or if they are opposites.  A stronger tile causes a weaker tile to disappear, and two opposites cancel each other out, causing them both to disappear.

I'm really liking this idea.  One of my concerns though is that the reactions make sense.  Most of them do; I think the opposites are intuitive enough, and with the order I placed them in I was pleasantly surprised to find that most of the strengths already make some sort of sense:  Fire burns Wood, Wood consumes Earth, Earth grounds Electric, etc.  There are only a few reactions that I'm not so sure of:

• Electric and Sonic as opposites - Sonic means sound waves or vibrations.  It sort of seems to make sense that it would be the opposite of Electric, but I'm not sure why.  I suppose at a really deep level you could think of it as the difference between particles and waves (Electric being electrons which are particles, Sonic being vibrations or waves) but maybe that's a bit too complicated to be intuitive?
• Metal beats Air - Why would Metal be stronger than Air?  I can't really think of any good reason, other than it just happens to turn out that way when you arrange the elements on the wheel.
• Air beats Sonic - This kind of makes sense; without air you can't have sound waves.  It's not as obvious as most of the other reactions though.
• Sonic beats Fire - Again, this is just the order it came in, and I'm not totally sure why Sonic should be stronger than Fire.  Unless of course you blasted a fire with sound waves that were strong enough to completely blow it out... which may be pretty cool actually.

I'm hesitant to change any of the elements or their order on the wheel, because that would then disrupt the other elements that already make sense in their current positions.  But maybe there are other elements that could be considered natural opposites to those that already make sense in their current positions.

I welcome any ideas that you think would make sense, as well as general feedback about the game design.  In the meantime, I've made a prototype of the game that is almost finished.  I'll post it here when it's ready to play!