A clock is heard chiming the half-hour in Westminster chimes. If chiming clocks were invented at the time of the action they wouldn't sound the Westminster chimes which date only - as the name suggests - from the installation of the Big Ben clock in 1859.
The trumpets making fanfares and announcements for the king and queen use very delicate, multi-layered harmonies. This is pure Hollywood, and would become a convention for many years in both ancient and medieval stories on film. They provide a lush musical punctuation that never existed, and still doesn't, other than in certain military band performances.
(At about 54:20) When Polonius touches a curtain in the background, he turns and addresses Claudius or Ophelia, but for a few seconds, his mouth is moving with no dialogue, until "Let's withdraw, my lord," is finally heard.
(At about 24:10) While Polonius talks to Ophelia by an arched doorway, at one point his mouth opens in speech, but there is no dialogue.