Any alternative to Radio Shack sound level meter?

The easiest I've used is a free download app called audiotools.  It provides a sound level meter and also real time analyzer adn fast fourier transform tools.

You can see gaps in your system and room.  I use the stereophile test cds and play pink noise or other signals to see where the system and room is lacking.

not complicated at all and quite easy and simple to use.

Not professional quality because you are using your Ipad or Iphone's microphone, but it works pretty well non-the-less.

enjoy

Minorl, It is easy to see the problems but much harder to fix them.

Kijanki, don't feel bad. It always looks awful. When I show people what their system is actually doing they usually puke. Remember a lot of the variation below 150 Hz is room effect. If you move the microphone three feet in any direction it will look totally different. 

You are absolutely correct.  But, if you don't know what the problems are especially peaks and holes in your system/room response, you are stabbing in the dark.

but, you are right.  fixing it is serious business.  Room correction has got to be the most difficult mind numbing expensive experience.  not for the faint of heart.  The good thing is if you know the problems, it is no longer trial and error.  

enjoy

mijostyn, thank you.  I know there is something wrong with my room response, but I will fix it later.  At least I have tool. My room is too reflective.  I don't hear any particular resonances but listening louder makes sound less clean.  It is most likely multiple echo, that it is reduced at low volume levels (further echoes fall below hearing threshold).