It's not only typical, for the audit committee, it's REQUIRED. And it will soon be REQUIRED for the compensation committee as well.
Better read up on Sarbanes Oxley.
http://www.soxtoolkit.com/sox-aud.htm
Also, check out the Dodd - Frank law
http://www.sec.gov/news/press/2011/2011-78.htm
Please SGE1, do some homework before you post! That would help you to be much more credible and informative. TIA.