Does Shakespeare use humor for comic relief in the banquet scene of "Macbeth", as he does in the earlier scene with the porter?

In Act 2, sc. 3, Shakespeare breaks up the tension of the
play with the comical scene of the exchange between the Porter and Macduff when Macduff
arrives at Macbeth's castle to get Duncan.  This is typical move on Shakespeare's part. 
During the banquet scene in Act 3, sc. 4, there is no humor.  When Macbeth sees the
ghost of Banquo sitting in his seat and no one else sees the ghost, it is not humorous,
it is showing us Macbeth's current mental state.  The scene shows how much guilt Macbeth
feels over having had Banquo, his good friend, killed.  Shakespeare isn't trying to
create humor when he has Lady Macbeth make excuses for Macbeth's behavior; he is showing
how Lady Macbeth has to cover for her husband.  These actions show us the level of
desperation of both Macbeth and Lady Macbeth.