The procedure previously documented for Mountain Lion etc has (again) been discarded by Apple for Yosemite. An immediate consequence of this is that pvoc anal and related programs creating frequency domain files will fail with an error message.
We are in the final stages of updating the whole CDP system to default CDP_SOUND_EXT to wav, but in the short term there is a new recommended procedure. Create a standard text file (e.g. using TextEdit.ap) called "environment.plist" with the following content:
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
<plist version="1.0">
<dict>
<key>Label</key>
<string>my.startup</string>
<key>ProgramArguments</key>
<array>
<string>sh</string>
<string>-c</string>
<string>launchctl setenv CDP_SOUND_EXT wav</string>
</array>
<key>RunAtLoad</key>
<true/>
</dict>
</plist>
Copy this file to your Library/LaunchAgents folder and reboot.
There is every possibility that this will also work for Mountain Lion and Mavericks too, but I am no longer able to confirm that first hand.