Engineer
talks to Orleans wind panel about noise
Charles E. Ebbing, retired engineer with
Carrier Corp. with nearly 50 years' experience, explained
the source and stress effects of low-frequency noise to the
committee, which met Tuesday night. Low-frequency noise
ranges from a few thousand hertz down to nearly zero hertz.
"A house shuts out all high-frequency noise and allows in
only low-frequency," he said. "The noise level of
low-frequency can be greater inside than outside, because
of the resonance inside buildings."
March 26, 2009 by Nancy Madsen in Watertown Daily Times
LAFARGEVILLE - An acoustic engineer told the
town of Orleans wind committee that low-frequency noise
needs to be measured and controlled as part of any zoning
ordinance created.
Charles E. Ebbing, retired engineer with Carrier Corp. with
nearly 50 years' experience, explained the source and
stress effects of low-frequency noise to the committee,
which met Tuesday night. Low-frequency noise ranges from a
few thousand hertz down to nearly zero hertz.
"A house shuts out all high-frequency noise and allows in
only low-frequency," he said. "The noise level of
low-frequency can be greater inside than outside, because
of the resonance inside buildings."
He observed that very few acoustical engineers have worked
on low-frequency noise.
Besides the decibel level, Mr. Ebbing pointed to other
types of problems with noise.
"The meter doesn't measure what you hear," he said. "It
measures the energy of the sound pressure. It doesn't
measure annoyance, only loudness. It doesn't measure
quality."
Mr. Ebbing said that heating and air conditioning systems
often are required to be quieter if they have an impulsive
or tonal quality.
He said measurements of both audible, or dBA, and
low-frequency, or dBC, noise should be conducted. Those
measurements then should be compared to each other by
subtracting dBA from dBC. If dBC is greater than dBA by
more than 25 decibels, the noise will have a rumbling
quality.
In working with air conditioning systems, Mr. Ebbing has
seen the effects of low-frequency noise. He said that its
rumbling quality increases stress, distraction and, in
homes, sleeplessness.
He said a law to protect people should include initial
measurements, compliance checks afterward and regular
monitoring as the years pass.
Mr. Ebbing reiterated that ambient background noise in
rural areas is as low as 24 decibels at night. According to
the wind industry, a typical wind farm is about 44 decibels
at 1,500 feet. So the noise at night would be increased by
about 20 decibels.
Noise explanations from the wind industry say rural areas
are quiet when there is no wind and turbines don't generate
power when there is no wind.
"They're implying that when the wind is blowing and the
turbines move, they will create noise but there will be
other noise to cover it," Mr. Ebbing said. "They're wrong
in that most of the time we can have no wind blowing at the
ground but have wind higher up, so wind turbines can turn
when we don't have other noise at the ground."
The next committee meeting will be at 7 p.m. April 14 at
the town offices.
Web link: http://www.watertowndailytimes.com/article/20090326/NEWS03/303269953/-1/NEWS