`require': cannot load such file -- audiooutput

Just installed libao-ruby for the first time. Attempting to run the sample program that is included.

/usr/share/doc/libao-ruby1.8/examples$ ruby1.9.1 ./test.rb
/usr/lib/ruby/1.9.1/rubygems/custom_require.rb:36:in `require': cannot load such file -- audiooutput (LoadError)
 from /usr/lib/ruby/1.9.1/rubygems/custom_require.rb:36:in `require'
 from ./test.rb:3:in `<main>'

$ lsb_release -rd
Description: Ubuntu 12.04.1 LTS
Release: 12.04

$ apt-cache policy libao-ruby
libao-ruby:
  Installed: 0.1-1ubuntu3
  Candidate: 0.1-1ubuntu3
  Version table:
 *** 0.1-1ubuntu3 0
        500 http://us.archive.ubuntu.com/ubuntu/ precise/universe amd64 Packages
        100 /var/lib/dpkg/status