Congressional Hearings available at Middlebury are included in MIDCAT (1976+) and LibrarySearch. Hearings are increasingly being digitized and included in Hathitrust archive. Recent hearings can often be found on Congressional Committee websites.
In addition, try:
What is the difference? These publications are described and can be searched on the collection pages provided by the U.S. Government via FDsys:
These can also be found using the Serial Set (except prints) and Congress.gov.