Trajectory of the soundscape

 kw: book reviews, nonfiction, science, acoustics, sound, noise pollution, silencing

Summer nights we hear mostly katydids, my wife and I. In late spring, there will be a few. By late July there are myriads, and they out-shout the annual cicadas ("locusts" to some). Just by listening through a slightly opened window we can tell how warm it is outside: at a comfortable temperature, they sing their usual 3-part song, "katy-did"; when it is uncomfortably warm for me, we hear "katy-didn't"; cooler temperatures elicit only a 2-part song ("katy") and the coolest temperatures at which they will sing (around 60°F) they just burp "kate!".

The earliest noisy ancestors of katydids lived about 350 million years ago, about twice as long ago as the earliest dinosaurs. Animals probably made inadvertent sounds as far back as a billion years or more, but we don't know of specific hearing structures prior to about half that.

We learn the history of sound and sound-making by living beings in the early chapters of Sounds Wild and Broken: Sonic Marvels, Evolution's Creativity, and the Crisis of Sensory Extinction, by David George Haskell. This book is lyrically written, celebrating the sounds of living things of every kind. The author also laments the gradual silencing of the natural world, and then goes on to point out the ways dominant human cultures silence others.

Many of the sounds animals make go unheard by humans. Firstly, the sonic realms we call "ultrasonic" (frequencies above about 20,000 Hz, such as the laughter of mice or the echolocation beeps of bats) and "infrasonic" (below about 15 Hz, where most elephant-speak occurs) cannot be perceived with our natural auditory systems. Secondly, we are very badly equipped to hear with our head under water, although we can hear some louder sounds such as the whistles and creaky-door sounds of nearby dolphins. But when out of water, we hear nothing: sounds made underwater stay there (kinda like "staying in Vegas").

The ears of land animals are elaborate transducers between airborne sound and the liquid environment in our inner ears. Most hearing is mediated by ciliated cells, which first evolved 3+ billion years ago, in the oceans. They are most sensitive to waterborne vibrations.

We humans go to great lengths to have quiet living spaces. I live in a suburb that is noted for being very quiet, at least from human noises. We do hear, blocks away, the occasional siren, and a bit of road noise. Otherwise, we hear a small amount of birdsong and insect noises. Bird song here is less by far than what I heard as a child in the 1950's and 60's. As I wrote above, summer nights can be noisy with insect sounds. Not just katydids but several kinds of crickets. Once I put a small microphone at the focus of a curved reflector taken from a desk lamp, and went about the yard pointing it here and there. I was amazed at the multitude of very high-pitched sounds, like crickets but 2-3 octaves higher. Being on the edge of hearing anyway, these sounds are usually too faint to hear.

But not that many of us have the luxury of a quiet home. Cities are noisy. VERY noisy. As the author brings out, the historical development of cities has resulted in poorer areas being the noisiest. It's almost an exact relationship. By that measure, the oceans are becoming impoverished. Human noise fills the seas. If the designers of ships' propulsion systems were required to spend a cruise wearing earphones attached to hydrophones placed on the ship's keel, they'd probably be permanently deafened within a day by the noise from the screws (propellers); I hope then they'd me more inclined to design quieter systems in the future! A single oil tanker or container ship, powered by multiple motors the size of houses, makes as much noise as a city. Multiply that by about 6,000 mega-ships, plus another 60,000 "smaller" commercial vessels afloat at any one time, and you have a sonic apocalypse. It is growing steadily. No wonder whales aren't rebounding that much. They did in the past—just for the past few decades—, but that has leveled off as our commerce fills their world with literally deafening racket.

This big book (400+ pages) is filled with wonderful information I've skimmed past or skipped here. We need sound, and we need a balance of louder and quieter places in our life; and so it is for all creatures. The sounds of animals are so many and varied and amazing, it is good to be able to hear them. That includes, not just taking an evening stroll amidst the thrums of katydid and cicada and cricket; not only going outside at dawn for the dawn chorus of bird song; even going to Cape Henlopen or Cape May when dolphins are passing and going under to listen to them. It includes being attentive to what is around us, not just sights but sounds and even smells.

I don't know what else to say about this amazing book. It's big, and I could have done with an even bigger book.