Misc: The effect produced when sound is reflected back is known as a(n) ?

Questions

In 1181 Supernova observed by Chinese and ---------- astronomers. ?

In 1697---------- , Holy Roman emperor (1742-45), born. ?

In 1806 Holy ---------- Empire ends. "it was neither holy, nor Roman, nor an empire." -- Voltaire ?

In 1809 ---------- Lord Tennyson, poet laureate of England, born. ?

In 1809 Alfred ---------- Tennyson, poet laureate of England, born. ?