[Cob] Soundproofing cob on a bamboo lath?

[Raduazo at aol.com]

    I do not know if this would help, but I just did a cob wall over bamboo 
lath. Bamboo was split with a conventional 5-way splitter and applied to a 
conventional stud wall using "horse shoe nails." That is the U-shaped nails 
sometimes used for attaching fabric or wire to a wall. You need to use these nails 
because bamboo splits and pulls away from ordinary nails, and you need to hold 
the nails in a pair of needle nose pliers to drive them. 
    This was then covered with a layer of cob with chopped straw pushed 
through the openings in the lath, followed by a layer of straw/clay plaster, a 
layer of horse manure/clay plaster and a final lime plaster.
    The resulting wall is much more massive than a conventional drywall 
surface. I think it is important that the inner layer of the wall has a different 
harmonic frequency than the outer wall to block sound. Plus I have conventional 
insulation between the walls.
    I did not do enough of this to determine if it was of any acoustical 
significance, but it should cut sound, and the wall cost less than $1.00 since the 
bamboo, the clay, the straw and the sand were all free. I am still on my 
first bag of lime for a 10 x 9 foot cob wall and a 3 x 9 foot bamboo lath. The 
store bought lime is the only ingredient that cost money.
Ed