There’s a list of books a cultured person is supposed to have read. Its size and composition vary depending on who you ask, but roughly speaking there exists a Western canon containing works by authors with names like Shakespeare and Dostoevsky and Milton and Sophocles. There’s something of a Nerd Canon too. The names of the authors of its works are more like Asimov and Feynman. It’s a list that’s certainly not all science and science fiction, though those are much more strongly represented than in most general lists. To me knowledge no one has ever written such a list up, but it exists as part of the zeitgeist of our subculture.
One of the names on the list is Neal Stephenson. I would say he has at least two books on the list: Snow Crash and Cryptonomicon. The latter is an awe-inspiring work, one of those rare books that truly left me a slightly different person operating in a larger and richer universe. The former is a book I am rather embarrassed to admit that I haven’t read. At this very moment, I’m one hundred and eighty-three pages into fixing that. It’s a fantastic book thus far.
At one point the protagonist – Hiro Protagonist is his name* – has a brief conversation with a famous Japanese rapper named Sushi K. Hiro talks with Sushi K in his car while the previous act is still on stage having an immensely loud concert.
Sushi K rolls down the window. The decibel level quintuples in an instant. He stares at the crowd, five thousand potential market shares, young people with funkiness on their minds.
It’s possible to interpret this two ways. The crowd sees him and gets louder, or the crowd is already loud and rolling down the window happens to let the sound in. Now Stephenson knows his physics, so either way he’s not going to get this wrong. But is he being literal or metaphorical? A decibel is a way to describe a ratio. Many quantities – sound in particular – comes in such a wide range of intensities that it’s almost pointless to use a simple linear unit of measurement like watts per square meter, and in any case it’s the differences in levels of sound that are often more important than any absolute unit of measurement.
The decibel scale exploits these properties by measuring on a logarithmic scale. Popping the defining equation for a decibel level L from Wikipedia:
Two sounds with two intensity levels P have their ratio expressed as L decibels. Making a sound 10 times more intense means increasing its level by 10 decibels. Thus a 90 dB sound is actually ten times more intense than an 80 dB sound. That doesn’t actually mean your ears will perceive the sound as ten times louder, your ears follow a more complicated pattern.
Since a decibel is defining a ratio it’s not actually meaningful to say a sound is “50 dB” by itself. When you heard a sound given that way without a reference, it’s actually implied that it’s 50 dB more intense than a particular reference intensity arbitrarily defined as 0 dB, which generally is roughly a very quiet sound at the threshold of hearing. In SI units this happens to be about 10^-12 watts per square meter – a tiny, tiny power flux.
A conversation such as the one Hiro was conducting might be around 50 dB. Multiplying the power level by a factor of five would only bump the sound up to about 53 decibels by our above equation. Multiplying the decibel level would give us 50*5 = 250 dB. This happens to be multiplying the actual sonic power by a factor of some 10^20, which corresponds to about ten trillion or so watts per square meter. I expect that would vaporize the entire concert just about as well as a thermonuclear explosion.
And if Stephenson meant the 120 dB or so of a rock concert was quintupled to 600 dB, well, that’s more than a bit worse, since it’s 10^(600-50)/10 times more power than the voices of the conversation. That’s a huge number. Every square meter would correspond to a power flux greater than the output of every star in the galaxy – by a lot.
As I said, Stephenson knows his science. Thus it’s pretty safe to declare this sentence a metaphor.
*This isn’t just lampshade hanging, by the way; it does make sense in the context of the story. The story itself is perfectly serious, while the setting is slightly self-aware. It would be overstating things to say Snow Crash is to Neuromancer what Sin City is to classic noir, but it would at least be in the neighborhood.