Gem installation ruby-audio failing

I have cloned an existing repository and am now running bundle install - for some reason it fails at the ruby-audio gem.

Installing ruby-audio (1.6.1) with native extensions 
Gem::Installer::ExtensionBuildError: ERROR: Failed to build gem native extension.

/Users/thisuser/.rvm/rubies/ruby-1.9.3-p194/bin/ruby extconf.rb 
checking for sndfile.h in /opt/local/include,/usr/local/include,C:/Program Files (x86)/Mega-Nerd/libsndfile/include,C:/Program Files/Mega-Nerd/libsndfile/include... no
checking for sf_open() in -lsndfile-1... no
checking for sf_open() in -lsndfile... no
*** extconf.rb failed ***
Could not create Makefile due to some reason, probably lack of
necessary libraries and/or headers.  Check the mkmf.log file for more
details.  You may need configuration options.

Provided configuration options:
--with-opt-dir
--with-opt-include
--without-opt-include=${opt-dir}/include
--with-opt-lib
--without-opt-lib=${opt-dir}/lib
--with-make-prog
--without-make-prog
--srcdir=.
--curdir
--ruby=/Users/thisuser/.rvm/rubies/ruby-1.9.3-p194/bin/ruby
--with-sndfile-dir
--without-sndfile-dir
--with-sndfile-include
--without-sndfile-include=${sndfile-dir}/include
--with-sndfile-lib
--without-sndfile-lib=${sndfile-dir}/lib
--with-sndfile-1lib
--without-sndfile-1lib
--with-sndfilelib
--without-sndfilelib
extconf.rb:26:in `<main>':   Can't find libsndfile (http://www.mega-nerd.com/libsndfile/) (RuntimeError)

  Try passing --with-sndfile-dir or --with-sndfile-lib and --with-sndfile-include
  options to extconf. If there are spaces in the path on windows, it may not work.

Gem files will remain installed in /Users/thisuser/.bundler/tmp/5253/gems/ruby-audio-1.6.1 for inspection.
Results logged to /Users/thisuser/.bundler/tmp/5253/gems/ruby-audio-1.6.1/ext/rubyaudio_ext/gem_make.out
An error occured while installing ruby-audio (1.6.1), and Bundler cannot continue.
Make sure that `gem install ruby-audio -v '1.6.1'` succeeds before bundling.

Honestly, I have no idea whatsoever what to do with this. Googling showed the same error with the mysql gem, and the solutions were mysql specific.

Has anyone ever stumbled upon this? If not, is there a way to tell rails explicitly to ignore that gem? Removing it from the gem file and running bundle install again did not do the trick.

Thanks for any help!

Edit

After running brew install libsndfile I got the following output:

Warning: Your Xcode (4.5.2) is outdated
Please install Xcode 4.6.
==> Downloading http://www.mega-nerd.com/libsndfile/files/libsndfile-1.0.25.tar.gz
Already downloaded: /Library/Caches/Homebrew/libsndfile-1.0.25.tar.gz
==> Patching
patching file programs/sndfile-play.c
==> ./configure --prefix=/usr/local/Cellar/libsndfile/1.0.25
==> make install
make[1]: *** [sndfile-play.o] Error 1
make[1]: *** Waiting for unfinished jobs....
brew: superenv removed: -g -O2 -Wall -Wextra -Wdeclaration-after-statement -Wpointer-arith -Wstrict-prototypes -Wmissing-prototypes -Wcast-align -Wcast-qual -Wnested-externs -Wbad-function-cast -Wwrite-strings -Wundef
brew: superenv removed: -g -O2 -Wall -Wextra -Wdeclaration-after-statement -Wpointer-arith -Wstrict-prototypes -Wmissing-prototypes -Wcast-align -Wcast-qual -Wnested-externs -Wbad-function-cast -Wwrite-strings -Wundef
make: *** [install-recursive] Error 1
Your Xcode and or CLT are mis-configured. Try some or all of the following:
    xcrun --kill-cache
    xcodebuild -license
    sudo xcode-select -switch /path/to/Xcode.app

I tried all of the suggested commands - to no avail. What else can I do to solve this?

So, we got it working together, and I thought I'd share the steps I had to take to make this work. Thanks to all the guys who commented!

The problem was that while installing the gem, it couldn't find the libsndfile
To install it, I had to run brew install libsndfile (install homebrew first if you don't have it already), which didn't work, so I had to...
... update Xcode to the latest version and install Xcodes command line tool (don't ask me why, but I had to.)
Then I ran brew install libsndfile, which worked
And last but not least I ran bundle install again, which finally installed the desired gem.