[Strawbale] Sound insulation with regards to a recording studio

[Walter Faas]

Dear balers,

It has been quite a long time since I last posted something
on this mailinglist. I have been working hard on my study
and didn't manage to keep up with recent developments
(which are undoubtly taking place even while writing
this!).

Currently I'm working at an architect agency. In one of our
projects we have to design a recording studio in an
existing building (1920's). Given the fact that the
 recording can produce up to 100 decibel and there will be
a school nearby, we need to focus heavily on sound
insulation. At the moment I'm doing some research on
suitable materials and I just cannot resist seriously
looking into strawbales. 

While travelling through time I found myself reading some
posts from june 2004 which contained information about the
soundinsulation of strawbales. I found that the typical
Rw-value of a strawbale construction according to ISO 140-3
was about 55 dB(A). This was a normal 2-string bale with
35/25mm plaster applied. To pass for a building permit we
must get a Rw-value of about <57 dB(A). This minimum
standard probably won't be sufficient to achieve a
comfortable area around the studio. We're striving for
about 65 dB(A) at the moment.

Does anybody have data about soundinsulation and/or has
pointers about the true limit of pure strawbale building
(just straw and plaster, that is. No fancy and expensive
acoustic materials applied) ? I'm looking for insulation of
the low-range frequencies since these are hardest to
insulate. I know of the soundstudio in Germany. Is there
any information about that project somewhere (I can't seem
to find more than pretty pictures)?

Kind regards,



Walter Faas