1) Does the sound work on the PC when you are not gaming?
2) Has the sound ever worked for Wolfteam?
Try the following instructions:
Check that your volume on your computer is not muted. Take a look at the task bar. Locate the icon that looks like a speaker. Click on it. If the mute button is pressed, click it to un-mute your computer. If your mute button is not pressed, make sure the speakers are turned up. If they are turned up and you still hear no sound, move on to Step B.
Open Device Manager on your computer. Click "Start" or the Windows icon, then click "Control Panel." On the Control Panel menu, select "System and Maintenance" and then click "Device Manager." Provide confirmation if prompted. Click on the "Sound, video, and game controllers" category in order to expand it. Look to see if a sound card is listed. If not, you will need to install a sound card.
Look for a exclamation mark next to the name of your sound card. If there is a yellow question mark, right-click the sound card and click "Properties." Make sure the general tab is selected, and check the status of the device (in the Device status box). Go through the required steps to repair the sound card. Firstly, right click on the sound card and make sure the device is enabled, if not then enable it. Secondly, right click on the sound card and update the driver software. Select the "Search automatically for updated driver software" option. If you do have a sound card installed and there are no errors, but you still have no audio, see Step D.
Check to make sure your speakers are plugged into the correct jack. If you have a USB device, it should plug into any USB port, but if you have a 1/8 inch cable, there is a specified jack for it on the back of the computer.
Manually update your sound card driver
You may require a re-install of the game as the sound files have become corrupt.