When you synchronize footage of the same event recorded with multiple cameras, the audio track from each source is used. If all your footage is of the same event and was recorded at the same time, the audio tracks will all contain more or less the same audio.
Follow these guidelines to get the best synchronization results:

• Automatic video synchronization works best with short objects. Trim your source files before synchronizing so that each object is 30 seconds long or less. Your trimmed objects should more or less line up with each other temporally so that the program can use the waveforms to find which objects go together. 
• To perform an automatic synchronization, hold down the Ctrl key and select each object. Right-click one of the objects and select "Audio functions" > "Align other audio objects with this track".
• If automatic synchronization doesn't work, you can also manually synchronize your footage using the waveform. Look for an easily recognizable peak in the waveform of each object and line up the objects so that the peaks line up. 
• If this doesn't produce the results you want, try placing snap points on a part of the waveform that stands out by right-click the waveform and selecting "Snap point" > "Set snap point". Now, move the objects so that the snap points snap into place and are lined up with each other.
• Then, group the objects to prevent them from being moved independently. To do this, select the objects and click the chain icon in the toolbar.
• When you're finished synchronizing, you can extend the left and right sides of the objects to return them to their original lengths.