為何提琴身的開口是個f形呢？

http://www.openculture.com/2016/01/why-violins-have-f-holes-the-science-history-of-a-remarkable-renaissance-design.html

the more elongated the sound hole, the more sound can escape from the violin. "What's more," Chu adds, "an elongated sound hole takes up little space on the violin, while still producing a full sound—a design that the researchers found to be more power-efficient" than previous sound holes.

論文在此 http://rspa.royalsocietypublishing.org/content/471/2175/20140905

反之，隔音呢？喇叭的低音反射孔呢？