I have had this issue also. the only way around this that i have found is to uninstall the sound driver on the original image and then push the image up. after every image comes down on what ever model you would have to install the audio driver manually.
I have a folder with post image installs like audio, wireless and video. the wireless and video are so the applications are installed on the machine. depending on what model dell we get it could be an intel based wireless card or nvidia wireless card. it just makes it easier for me to install the drivers after the image comes down.