Right to Quiet Society Noiseletter
Winter 2009 - page 3

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Expert's comments on sound-proofing solutions

By Clair Wakefield

I was checking out the Fall 2008 issue of your NOISE-Letter and I have a few comments:

  • The article "Sound‑proofing solutions for your home" contains many useful general suggestions. However, it repeats the familiar QuietRock promotional line that "One sheet of QuietRock is equivalent to 8 sheets of ordinary drywall."

    Taken at face value, the "8‑sheets" claim would, within that portion of the audible frequency range where the response of the wall or floor to sound-waves is "mass‑controlled", indicate that the Transmission Loss (i.e. the decibel reduction in the level of a sound upon passing through a wall) of the single sheet of Quiet Rock would be 18 dBA greater than that through a single sheet of normal drywall. This  is quite an accomplishment—corresponding to about a 60‑fold reduction in sound energy and almost a quartering of perceived loudness.
  • While achieving effects of this magnitude may be possible in some ideal situations, it will really depend on the nature of the wall or floor to which the QuietRock is to be added to or included within, as well as any other sound paths (e.g., flanking paths around the main noise barrier) that may be involved.

    We have had only one opportunity to test QuietRock in the field. It involved the addition of two layers of QuietRock (3/4" I believe) to one side of an existing wall between two different offices.  While field tests are always a challenge, due to flanking and other issues, the resulting improvement in noise reduction across the wall was no where near 18 dBA; rather it was more like 6 dBA.

    Given the very high cost of this product, I would not want to support the claim that it will produce such dramatic effects wherever it is applied. If you have any reports (quantitative or qualitative) about how well QuietRock has performed in the field, I would love to read them.

  • I have not had a chance to test the effectiveness of Green Glue, but at the recent CAA 2008 meeting I observed its effects in damping the vibration of gypsum-board sheets when struck with a mallet, and it was quite impressive. It certainly seems to create an effective constrained‑layer damping situation, and its literature shows more realistic, but still impressive, improvements of about 6 points (dB) in STC ratings for staggered-stud and single-stud walls.

  • As a way of giving folks access to unbiased info about how to control noise both from the outside and inside of their homes, they could be referred to the "SoundSmart" noise-control manual, which Wakefield Acoustics <www.wakefieldacoustics.com> prepared a few years back for the City of Vancouver. It is available in both a brief booklet form and as a full manual from the City's website <www.vancouver.ca/soundsmart>.

Note:  The National Council of Acoustical Consultants (NCAC) is a professional group of acoustics experts and consultants. To find one in your area, please check out the NCAC membership list at <www.ncac.com>.

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Goats substitute for lawn mowers

By Bob Pool

Los Angeles – The hills were alive with the sound of munching. In fact, the only things that seemed missing when a herd of goats climbed up a weed-choked lot in the high-rise district of downtown Los Angeles were Julie Andrews and the von Trapp family singers.

Leaders of the Los Angeles Community Redevelopment Agency hired 100 goats to nibble away thick weeds on a steep slope next to the Angels Flight funicular*. Agency officials said the goats were cheaper and more environ-mentally friendly than two-legged brush-clearers armed with gasoline-powered weed-whackers. And they are much more fun to watch, downtown office workers and other passers-by quickly decided, as the animals fanned out over the 45-degree slope and chowed-down.


Commuters emerging from the Red Line subway who came face to face with the goats reached for their cell-phones and snapped pictures. “My friends won’t believe this unless they see it,” said Vicky Bravo, a student who lives south of downtown. Sam Vera, an auto repairman, pulled a digital camera from his backpack to photograph the grazing goats with a glass-walled high-rise gleaming above them.

“This is absolutely beautiful. It’s a wonderful contrast to the buildings around here,” he said. The goats were being rented for US$ 3,000. The cost of hiring workmen to clear the 2½-acre hillside would have totalled as much as US $7,500.

[*The Angels Flight funicular, known as “The shortest railway in the world” carries passengers up and down Bunker Hill, between 3rd and 4th Streets, in Los Angeles.]

Request for reinstatement of noise-control office in the EPA

With a new president taking office in Washington, D.C., we urge all our members in the USA to write to your political representatives to endeavour for the reinstatement of the noise-control office in the EPA. Its funding was cut by President Reagan’s administration, which discontinued all relevant work so vital to keeping noise under control.

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