Neighborhood buzz

Does your neighborhood have a buzz on? Mine does, and has had for more than a year. When I first became aware of the low bass background noise, I wasn't sure if I was imagining it or not. My hearing's above average, so not having anyone else notice or confirm it didn't answer the question. I'd wake up in the middle of the night and try to figure out if I was hearing blood rushing in my ears or wonder if my low-end perception had slipped over the fine line to thermal vibration. In spite of being two rows of houses away from a busy street, our neighborhood is surprisingly quiet, in general. 30 and 40-year old trees are an important part of the sound damping.

The source of the noise (if it was indeed real) was not easy to track. I know the equipment in the house (refrigerator, furnace fan, attic fan, etc.) well enough to rule all that out, but stepping outside makes it "go away," masked by the larger soundscape of city, wind in leaves, etc. We had new, improved, double-pane windows installed last year, and they reduced the level some, but did not stop it completely. One of our neighbors has lots of power tools, and a never-ending stream of projects, but it doesn't seem that their appliances could supply the pattern of sound, either. I know what their air compressor sounds like as it starts and stops to top off its tank. And a refrigerator or freezer would exhibit some sort of duty cycle.

Much of the time, it was below awareness and out of mind. This is not at the level that would trigger an ordinance, or a psychological study. I'm sure we're still among the "quiet areas" with sound levels below 50 dB. But home sick for a couple of days, and spending more time in the house, I find that it is indeed real, and that its intensity has increased. Jeanette now recognizes it as well. We've lived in this house for the last 18 years (with 2 years off for good behavior), and this is something new, a disturbing change in what have been generally peaceful surroundings. It's not just traffic noise, else it would ebb and flow with a daily pattern, and be close to nonexistent in the wee hours of the morning. We do have more and busier arterials within earshot, but this feels closer than the mile+ that impinges on us outdoors. A car idling by a neighbor's house augments it, but the absence of idling cars does not eliminate it.

The nearby shopping areas used to be much busier, with two grocery stores within a couple minute walk. The grocery stores are gone, leaving two gas & grocs (one with a car wash), a fast food and a slow food restaurant, a dry cleaners and an assortment of small shops. I'm guessing that among them is some mechanical equipment that runs most or all of the time and either transmits through the ground or utilities (the noise is perceptible in the basement as well as upstairs), or just happens to be tuned to the resonance of our walls. I know the sound (and duration) of the parking lot "vacuum trucks" (which seem to largely share the operating principle of leaf blowers - move the dust to everywhere but here), but the cleaning cycle is too intermittent to account for the general noise.

As you might have surmised, it's bugging me. I've been thinking about bringing home a spectrum analyzer from work to collect some data and see if I can track down the source. The Right to Quiet Society has some interesting links, including quiet getaways if it gets to be too much to bear. But in a brief web search, I didn't find anyone else talking about this sort of thing. My guess is, it's becoming more common as our cities take away our access to quiet as they have the dark.

Update, 10.Nov.2002

Someone who read this page asked me if I'd heard about the "Taos hum." I said I hadn't, but a quick web search turned up lots of hits on the phenomenon, including the Taos hum website. It sounds (!) exactly like what I described here, and includes an email forum with two years of reports from other hearers, in lots of different places: Crestline, Palm Springs, Los Angeles, Minnesota, Rio Rancho, Nebraska, Denver, Oklahoma, Calgary, Vancouver and Victoria BC, northern Idaho, Kokomo, Aurora, Bristol, Fayetteville, Salt Lake City, New Hampshire, Santa Barbara, Cleveland, Boston, Redding, Red Bluff, Tokyo, New York, southern Missouri, Georgia, Denmark, Pennsylvania, and on and on.

Update, 8.Dec.2002

I was in Spokane Valley over Thanksgiving, and noticed the hum up there. I also noticed a beat to it, and checked my pulse: same beat. That's not to say that all I was hearing was my own heartbeat in my ears; I think stochastic resonance from the background noise pushed that over the threshold of my perception.

From the current noise back in our neighborhood, it seems to me more like the combined noise from automobiles than ever. Filtered through modestly insulated residential construction, the high frequencies in the background are attenuated, and the low frequency comes through; a "low-pass filter." With reduced background noise, what remains is more perceptible. Opening a window (not really an option in Boise in December) raises the overall sound level enough to mask the low frequency component. A noise source in the house would work, too, and for those who are bothered by the hum, I'd recommend looking at white noise generators. In this case, more is less!

Tom von Alten      tva_∂t_fortboise_⋅_org

Sunday, 08-Dec-2002 17:10:37 MST