README.md in shelr-0.16.2 vs README.md in shelr-0.16.3

@@ -74,9 +74,15 @@
 
      brew install ttyrec      # OSX
      sudo port install ttyrec # BSD / OSX
      shelr backend ttyrec     # BSD / OSX
 
+To enable sound recordings, you need to install `sox`.
+
+     brew install sox          # OSX
+     sudo port install sox     # BSD / OSX
+     sudo apt-get install sox  # Ubuntu / Debian
+
 ## Copyright
 
 (Э) 2010, 2011, 2012 Antono Vasiljev and
 [contributors](https://github.com/shelr/shelr/contributors).