Sound files are in MP3 format. You will need an MP3 player, which you can download free.
Try QuickTime for PCs or Macs. (Quicktime is built into Mac OS 10. To download a version for earlier operating sytstems go to Apple Support.) You can also try WinAmp (PCs only).
Study tip: To record your responses use your computer microphone or a headset and open Sound Recorder, a free Windows program. (Click on the Start button and go to Programs › Accessories › Entertainment). You can also download free Audacity, a sound editor, player and recorder (PCs or Macs).
If you are unable to view video materials, you will need to download Flashplayer and Java, free programs, and make sure your browser is Java enabled. If you are still having problems, try another browser, such as Firefox/Mozilla or Google Chrome for PCs or Google Chrome for Macs.