Noise Reduction
Jan 24, 2023 03:44 PM Filed in:
Did You Know? | How Things Work
In my world, that of an audio engineer, noise reduction refers to eliminating background clutter, hiss, static, or other offensive sounds from a recording. Essentially it's the effort to make the recording sound clear and natural. But for the rest of the world, noise reduction means eliminating offensive human-made sounds from our environment, and we're doing a pretty lousy job of it.
I live in the city of Lexington. My home is situated between three hospitals, all of which have an ER and a helipad. I live on a feeder street that's 300 yards from one of the city's most traveled arteries. Anybody with a souped-up vehicle uses both of these roads while attempting to break land speed records. The university's 70,000-seat football stadium is 3/4 of a mile away, a high school's stadium complex is a half mile away. There's a summer outdoor concert series 2,000 feet away. A very busy train track is a thousand feet away. You can see where I'm going with this. Having a conversation on my front porch is like going to a rave.
Scientists and medical researchers have shown that frequent exposure to loud sounds can affect hearing, mood, mental health, blood pressure and heart disease. In other words, humans doing human things is hurting humans – and the animal kingdom. In my 2015 article "Shhh! Be Quiet!!!", I talked about the alarming disappearance of places on Earth that are devoid of all human sounds. Gordon Hempton has been on a decades-long crusade of identifying and preserving "quiet" places in the Pacific Northwest, like Olympia National Park's Hoh Rain Forest. Hempton's definition of "quiet" is a bit sobering: A natural environment that has no human-intrusion sounds for at least twenty minutes. Twenty minutes? That's all we get? That's sickening.
And speaking of sickening, my 2021 article "Sick and Tired of Sound" shows that one can't even escape the loud cacophony by humans in a hospital. Daytime sound levels measured at patients' bed locations reached 72 dB, and peaked near 80 dB – chainsaw level. The constant chatter of humans and hospital equipment is unhealthy for those trying to recover.
I complain about my neighborhood's noise level, but I'm glad that I don't live in New York City. Anybody who's been there can verify that it's a very loud place to be. The caverns created from skyscrapers seem to funnel and amplify sounds from many blocks away, crashing into residents like a flash flood in an arroyo. In my travels there, sirens seem to be the leading troublemakers. As I wrote in my 2016 article "A Siren's Song", emergency vehicles are increasingly louder, especially with the addition of a "low frequency system," or LFS. I call it "Loud F*@#$%^& Siren."
How do we, as a society, reduce the noise around us? One way is to have a pandemic. During the initial COVID-19 pandemic shutdown, the near absence of cars, trucks, trains, planes, and machinery in San Francisco allowed birds to lower the volume of their songs and tweet more complex mating calls. Outside of that gruesome scenario, cities must tackle the offenders at the source, instead of a wide swath of vague laws and ordinances that are impossible to enforce.
New York City has been experimenting with traffic cameras that employ microphones and sound level measuring devices. In the pilot program's first year, 71 people have been cited for loud exhausts. The NYC Department of Environmental Protection has now expanded the program to catch more offenders.
I mentioned that I live near a railroad crossing. In my 2021 article "Ear Training", I wrote about how trains use their horns to signal a warning at crossings, dominating the entire neighborhood. Some communities are installing warning horns at the crossing itself. In fact, my neighborhood crossing will be getting one of these newfangled warning systems in the near future. I'll welcome the change, but I admit that I will miss the charm of different train whistles, especially the vintage locomotive that occasionally chugs through.
Aviation is getting in on the act and giving aircraft the silent treatment. In a move to save on fuel costs and reduce carbon emissions, small short-range electric planes are being rolled out of test facilities. The world's first all-electric jet made its maiden journey last October. Although its range is only 440 nautical miles, electric aircraft like Eviation's "Alice" will compete with conventional jets and props in the regional air service sector. One benefit engineers are seeing is the reduced noise level of electric aircraft, as much as 16-22 dB lower in some tests.
What else can we do to reduce noise pollution? Block noise by using headphones, install thicker windows, or add sound absorption treatment in our homes and workplaces. But that still leaves everyone else fending for themselves. Reducing noise at the source is the key.
- Isolate and insulate loud machinery in special rooms.
- Around the house, close off doors to appliances and motors.
- Perform maintenance on machinery and oil gears as necessary.
- Install carpeting or noise-reducing flooring.
- Turn off appliances you're not using.
- Drive an electric or hybrid vehicle.
- Use electric lawn tools.
- Be active in your community and fight for more noise pollution laws and strict enforcement.
Tags: Noise reduction, Noise, Noise Pollution, Silence
