isn’t happening. In fact, I’ve learned that full habituation is a bit of a
pipe dream. Just because you don’t notice certain noises anymore
doesn’t mean your brain is not on some level responding to them.
Scientists and regulators used to be interested in noise pollution
because of the threat of hearing loss, which is real and happening to
many of us at younger and younger ages. But even at dramatically
lower volumes, noise poses risks far beyond our ear canals. In
fascinating studies, people have been hooked up to electrocardiogram
monitors while sleeping through plane, train and traffic noise.
Whether or not they woke up, their sympathetic nervous systems
reacted dramatically to the sounds, elevating their heart rates, blood
pressure and respiration. In one study that lasted three weeks, the
subjects showed no biological signs of habituating to the noise, and in
another study that lasted for years, the biological effects only got
worse.
THIS SUBCONSCIOUS VIGILANCE makes sense from an evolutionary
standpoint. Sleeping or hibernating animals must still maintain their
capacity to react to danger. It’s not uncommon in the animal world
for some species to lose their vision through evolution (like bats and
those seriously ugly fish at the bottom of the ocean) or their sense of
smell (like dolphins, or, increasingly, humans), but there are no
known examples of evolution driving vertebrate species to lose
hearing. This is our main “alerting” and “orienting” sense; it tells us
not only that something is out there but from which direction it’s
coming. Sound also triggers our strongest startle reactions.
Of course, nature didn’t intend roaring jet aircraft to be processed
by our nervous systems every sixty seconds. What does a loud
anthrophone do to us? The news is not good, not for us and not for the
birds, whales and other wildlife whose breeding and foraging habits
are upended by it. Numerous whale die-off events have been