What version of minecraft and forge are you trying to work with? Based on what I've seen of some of the code and examples I'd guess 1.6.1+. I verified that you can use .wav files without needing to register a codec first in MC 1.6.2 and Forge 789.
I'm betting you have a name and path issue. What is the console log showing you? Are there errors indicating your .wav file can't be found? Please remove the .1. from the file name and see if that helps
Numbers at the end of a sound file names are removed by MC so you can register several version of the same sound file and MC will play one of them randomly. It adds a bit of variety, e.g.
// You add sounds them the same way as you add blocks. Keep it all lowercase please for max compatibility.
event.manager.addSound("modname" + ":" + "soundfilename" + "1.ogg");
event.manager.addSound("modname" + ":" + "soundfilename" + "2.ogg");
event.manager.addSound("modname" + ":" + "soundfilename" + "3.ogg");
event.manager.addSound("modname" + ":" + "panflute" + ".wav");
// The location of my sound files in the development environment are as follows
// C:\Work\minecraftdev\mcforge1.6.2-9.10.0.789\forge\mcp\src\minecraft\assets\modname\sound
// Your final zip file would look like this
// <root of the zip>assets\modname\sound
// <root of the zip>modname\<class files>
// <rooy of the zip>mcmod.info
Your play code looks fine. Here's what I've used successfully.
// plays soundfilename1.ogg, soundfilename2.ogg, or soundfilename3.ogg randomly
target.worldObj.playSoundAtEntity(player, "modname" + ":" + "soundfilename", 1.0F, 1.0F);
// plays just the one .wav file
target.worldObj.playSoundAtEntity(player, "modname" + ":" + "panflute", 1.0F, 1.0F);
//
I'm pretty new to modding, but I hope this helps.