The audio tracks provide the necessary prompts for the speaking and writing sections, which are crucial for the "integrated" tasks where students must listen before they respond. Why the Audio Program is Essential
: Newer versions of the 4th edition (post-2014) may replace physical discs with an online access code for digital practice tests and audio files. Cambridge University Press & Assessment Why You Need It This audio is essential for mastering the Integrated Skills Cambridge Preparation For The Toefl Test 4th Edition Audio