Sound and Nihilism

[henryp]

We are physical beings analyzing a physical world.  Everything that exists, exists within it.

That seems rather parochial. Who’s to say that there are no other ways of existing and ways in which we unknowingly participate in them? People may be unaware of them now, but it seems premature to rule out the possibility.

We talk [of] meaning like it is an external [ ]measurable thing.  But what is meaning tangibly?

Must everything real be tangible? Is every real thing measurable?

It is our brains assigning values to our perception of the world. [/i]If you do not distinguish between the apparent difference between the physical processes of the brain and the qualitative experiences of the mind, you run the risk of begging the question. It assumes a mind-brain identity theory and closes off other options.

…that 'meaning' is not some intangible concept, it is a physical thing that exists.  It is a fact.  

A fact is propositional statement the contents of which are true. Do facts exist? If facts exist then you tacitly accept a category for intangible beings.

And when we are all gone, does meaning still exist?  No.

I don’t know. Does it?

…the conversion of the waves into sound in my brain is real.

Is the reality of a process, like converting vibrations into sound, somehow different from the reality of a sensible body, like an apple? Are you suggesting one category of being for processes and a different one for sensible bodies?

I'm not trying to write a proof with carefully picked out dialog that needs to be parsed line by line.  So if I use a word like "Fact" and you took some fancy argument class that says fact implies more than I intended to, oh well.  My bad for being a shoddy communicator.  But I'm hoping that as a whole my point is getting across in a very casual form, which I think it did.  I'm writing this pretty free form, to the point I'm often drawing new conclusions as I'm writing this stuff.  So I'd hope that you work with me on trying to understand my intent, rather than against me by trying to take vagueries and use them against me.  Probably asking a lot given the treatment of theists on this site.
That being said
1) I prefaced this as a discussion from the Atheist point of view.  In particular, that we are happy to dismiss God for not having any proof of existence, so we should probably be consistent in that in how we look at things.  I'm not really getting into what comes before this here.  
2) If our world view ends up being wonky or lacking, so be it.  This'll be ridiculously wrong.  But if we operated under the assumption that everything we know could be wrong to the point that we can't count on the 'known' laws of the universe, then we're not going to get very far thinking about anything.
3) Bit of a tangent on fact.  I'm not following.  Are you trying to say ideas and categorizations aren't tangible?  Ideas are certainly tangible.  Again, you'd just look to the brain we've got all kinds of words, thoughts, and definitions bouncing around in there.  
4) I don't think I was saying they were different categories.  I was equating both as input/output brain operations.