Pidr1nhu, the question was does the pronunciation change. If you say "I can read" and "I have read," the way you say "read" changes. But the way you say "beat" does not change. Also, as an American, I would say "They had beaten [down the grass to form ma path to walk on] more natural than "They had beat..." - What is the souce that say U.S. English uses "beat" for the past participle.