Check to see if your speakers are on and the volume is up. If you typically use headphones, check to see if they are plugged in. Your speaker may have a separate on/off button on it (or a turning dial that will increase the sound). There may also be a separate volume control on your keyboard.
You can control the overall level of sound using Windows. The easiest way to do that is to hit the or sound icon on the lower right of your screen and adjust the slider to the correct volume.
If you can not see the icon, here is another way to to change your sound settings: Click your Start button, choose Control Panel, choose Sounds and Audio Devices. Move the slider up or down to raise or lower the volume. You can also change speaker settings on that screen. Be sure to click "OK" when you are finished.
Check with your IT/computer staff on location to see if there may be other issues involving sound. Some offices may not have sound cards. There may also be specific sound settings at your office that may not be easy to change. The computer staff should be able to come right to your desk to help you assess the problem.