From Valve Developer Community
Note:Command parameters are described inside the
Play a sound where "
sound_name" is the specified sound with the path from <sound/>.
This will play the sound "stuck1.wav" in the folder "sound/common/".
Note:If you omit the file extension, it will also works if the file is a .wav sound.
Warning:If you trigger this command from a map in Hammer editor, never try to pass string parameters to a script function with this input. It will corrupt the VMF structure because of the nested quotation marks, which then must be removed manually with a text editor in order to recover your map.