Robert Krulwich | nhpr
It was July 15, 2009, in Ottawa when it happened. You didn’t have to be there, you could have been blocks away. Kiss, the band, appeared on stage and made what some say is the loudest sound ever produced in a live music concert. Their onstage speakers blasted music at 136 decibels, which, says science writer David Blatner in his book,Spectrums, is “the equivalent of standing next to a jet airplane taking off.”
The neighbors complained, and Kiss was forced to turn the volume down.
Turning sound up or down is tricky because decibels are logarithmic; a small change makes a big difference. The standard measuring unit is a “bel.” Nobody uses “bel” (named for the telephone entrepreneur Alexander Graham Bell), instead we use “decibel,” which is one tenth of a bel.
As you can see from this chart, for each additional ten decibels, ten times more power is required, but each step doubles the perceived loudness of the sound.
So you and I can have a normal conversation (about 40 decibels). That is about twice as loud as the sound of a quiet library (about 30 decibels), but the jump requires a thousand times more power. “A large truck driving by,” says David, “can throw 94 decibels, carrying almost a billion (10 to the 9th power) times the power of a whisper.
Decibel changes are inherently dramatic. The Kiss concert in Ottawa was, says David, “17,000 times louder and ten trillion times more powerful than a heartbeat.” So that’s loud.
But there’s louder. Much louder. In his otherwise quiet book, In Pursuit of Silencewriter George Prochnik describes a “dB drag race,” a sport that involves putting as many