Linux command in PHP

I have script that basically process a file. If something found in the file, the script send email. Today I tried to add another option, that gives sound and send email. The script works ok when I run from shell. But when I add the code to cronjob, the email is send but NO SOUND. Any ideas what can cause such problem? # Below the code that start the xmms sound $alert = "/usr/bin/xmms /home/mike/Desktop/song1.mp3"; `$alert'; _________________________________________________________________ Is your PC infected? Get a FREE online computer virus scan from McAfee® Security. http://clinic.mcafee.com/clinic/ibuy/campaign.asp?cid=3963