The 1964 tune "The Sound of Silence" by Paul Simon and Art Garfunkel is a bona fide classic, but it never really identifies just what this "sound of silence" is. That task instead falls to "In Pursuit of Silence," the documentary about this surprisingly hard-to-pin-down aural quality and why it's worth pursuing.
One thing quickly becomes clear: Silence is not simply a measure of decibels. Through a series of new and archival interviews with authors, scientists, musicians (most notably the composer John Cage, he of the famous "4'33""), Zen practitioners, etc., we learn the definition of silence can sometimes get downright spiritual. One historian makes the compelling case that the occasional retreat into quiet and solitude was once an essential part of the human experience — one that has been eroded by a modern society obsessed with constant visual and aural stimulation.
The second half of the film documents some of the tolls of our noisy modern life. Take a school in New York next to a train track, for instance, where students are falling behind their peers due to the interruptions (my mind immediately went to Okinawa, where jets flying overhead have caused similar problems) — or loud hospital emergency rooms, where garbled communication can literally lead to death.