I spent this weekend on the Appalachian Trail, taking a much needed break from New York City. Returning home I was struck, as always, by the volume of this place. There is a constant barrage of sound: from trucks, cars, construction vehicles, horns, subway cars starting and stopping, airplanes and helicopters overhead, air-conditioners in the summer and heaters in the winter - the existence of this hub seems bound up with noise.
Why is New York so loud? Can we have a quieter city with the same benefits? Noise, by definition, is wasted energy. Sound is the energy of vibrating airwaves hitting our ears and telling our brain something is up. These vibrations take energy, which of course, is neither created nor destroyed. Whenever we hear something, energy is being released into the environment, and unless we're hearing a radio or cd player, the energy is being wasted.
For example a moving truck has tremendous kinetic energy. When the truck comes to a stop, all the energy of motion has to go somewhere. The truck driver's brakes stop the wheels, and the mechanical energy is transformed into heat and noise, in an amount exactly equal to the force of the trucks motion (minus resistance forces like friction and gravity). Thus, the horrible squeals and grunts I wake up to every morning. Regenerative braking (more here) recaptures some of that energy, decreasing the heat and noise, and increasing the life span of a car's brakes and battery. Regenerative braking makes sense, of course only when you're storing energy in a battery onboard the car. This is why the technology is primarily employed in hybrids, although some conventional cars (BMW 5, 3 and 1 Series for example) use regenerative braking to help out the alternator.
As Kati Thompson reminded us, a key to environmental change is going to be presenting a picture of a greener world that will appeal to people. Based on talking to fellow New Yorkers, a quieter world certainly appeals. I got a taste of the future today walking to work: an SUV taxi drove past me, and I didn't hear a thing. This is not due to air-conditioner induced deafness (more on AC noise later) but because this was a hybrid cab. The car was driving slowly (as is nearly always the case in New York) and so exclusively using its electric motor. Mayor Bloomberg wants silence to be the sound of all taxis by 2012, and it can't happen soon enough for me. The electric motors in these hybrids will convert 50-95% of the chemical energy stored in their batteries into mechanical motion, compared to the 25% efficiency of conversion of the internal combustion engine. While this gap is not entirely attributable to noise, it seems the electric engine puts energy into my wheels instead of my ears.
Air conditioning is another instance where green technologies decrease noise. Green buildings enable air to flow through them, are opaque to the bulk of solar heat, and move heat into appropriate sinks. Decreasing the need for air conditioning eliminates the whooshing and buzzing I've been listening to all summer.
This is an instance where greater efficiency will not lead to greater usage of resources. If you can cool your house comfortably using little or no electricity, it won't prompt you to use that electricity otherwise - you'll spend the money elsewhere. If you can get to work using less gas, you won't drive more, you'll save the cash. Here's where we get to George Monbiot's point about green consumerism. If we just spend that money on plastic toys and paper from virgin forests, we're clearly no better than we started. If we spend that money on carbon remediation, or books printed on post-consumer waste paper (no trees needed!) we're going to start getting out of this mess.
