Structural Noise propagation

[sergioTOOL]

Hi

There is a plant room with a noise level of approx. 90dB(A). The room
´s boundaries are made of solid concrete. Does anybody know how to
calculate or arrive to an approximate value of how much noise will
leak to the room upstairs via the side walls (the room upstairs has
the same shape as the plant room, therefore the sidewalls are
aligned).
Like I said, the room´s structure is all solid concrete and there are
no pads or air gaps separating the side walls from the roof. I have
found values to determine the amount of isolation provided by the roof
as a standalone plank. But nothing related to flanking path
transmission via side walls like in this case.

Any help will be much appreciated.
cheers
Sergio

[gu_tar]

Post by sergioTOOL
Hi
There is a plant room with a noise level of approx. 90dB(A). The room
´s boundaries are made of solid concrete. Does anybody know how to
calculate or arrive to an approximate value of how much noise will
leak to the room upstairs via the side walls (the room upstairs has
the same shape as the plant room, therefore the sidewalls are
aligned).
Like I said, the room´s structure is all solid concrete and there are
no pads or air gaps separating the side walls from the roof. I have
found values to determine the amount of isolation provided by the roof
as a standalone plank. But nothing related to flanking path
transmission via side walls like in this case.
Any help will be much appreciated.
cheers
Sergio

Hi Sergio,

Unless the roof slab is very thick and has a very high acoustic rating
the noise via the roof/floor should be the dominant source with the
trans path via the walls being minimal.

The only exceptions would be if there was a severe amount of vibration
in the plant room this could transfer through the structure and
radiate into the room above from the walls and floor and roof of the
above room. Also if there was some external path ie noise out the
plantroom door then into the room door above via some path.


Cheers,
Tom

[Tony]

Post by sergioTOOL
Hi
There is a plant room with a noise level of approx. 90dB(A). The room
Žs boundaries are made of solid concrete. Does anybody know how to
calculate or arrive to an approximate value of how much noise will
leak to the room upstairs via the side walls (the room upstairs has
the same shape as the plant room, therefore the sidewalls are
aligned).

Look for "statistical energy analysis" (SEA). I certainly would not assume
that the flanking paths are not significant, as the total areas involved
could be a lot more than the floor.

[p***@msn.com]

Post by sergioTOOL
Hi
There is a plant room with a noise level of approx. 90dB(A). The room
´s boundaries are made of solid concrete. Does anybody know how to
calculate or arrive to an approximate value of how much noise will
leak to the room upstairs via the side walls (the room upstairs has
the same shape as the plant room, therefore the sidewalls are
aligned).

Look for "statistical energy analysis" (SEA).  I certainly would not assume
that the flanking paths are not significant, as the total areas involved
could be a lot more than the floor.
--
Tony W
My e-mail address has no hyphen
- but please don't use it, reply to the group.

I seem to remember a rule of thumb that you take the STL of the wall
and add 10 dB to it to calculate the flanking path contribution, but I
don't recall the source of that rule

[Tony]

Post by p***@msn.com
I seem to remember a rule of thumb that you take the STL of the wall
and add 10 dB to it to calculate the flanking path contribution, but I
don't recall the source of that rule

There is no rule of thumb. By understanding how energy is likely to
transfer or be reflected at boundaries, depending on the mass of the
partitions and how they are connected, it is possible to make some rough
predictions without going to a full analysis. But the only general rule
that I would apply is, the better the common partition is, the more
important flanking paths are likely to be. In studios that are designed for
high sound insulation, flanking will often dominate the sound insulation
performance unless special measures are taken, for example, "floating" the
whole room on springs.

[gu_tar]

Post by p***@msn.com
I seem to remember a rule of thumb that you take the STL of the wall
and add 10 dB to it to calculate the flanking path contribution, but I
don't recall the source of that rule

There is no rule of thumb.   By understanding how energy is likely to
transfer or be reflected at boundaries, depending on the mass of the
partitions and how they are connected, it is possible to make some rough
predictions without going to a full analysis.  But the only general rule
that I would apply is, the better the common partition is, the more
important flanking paths are likely to be.  In studios that are designed for
high sound insulation, flanking will often dominate the sound insulation
performance unless special measures are taken, for example, "floating" the
whole room on springs.
--
Tony W
My e-mail address has no hyphen
- but please don't use it, reply to the group.

Hi Tony,

In reference to my comment that the structural transmission is not
likely to be an issue compared to the transmission via the floor/roof
I would really say that this has been my experience for the past ten
year or so of working as a consultant.

You are right that the flanking paths are significant in a studio
situation but this is a specalist situation and it is unlikely that
someone is going to build a highly sensitive room next to a plantroom
(If you are please reconsider the location).

Anyway I am reading a book of structural sound transmission at the
moment by Fahy. I used to have access to AutoSEA and I have built a
few models for vessels with that, When doing analysis on the AutoSEA
model for room to room transmission via structural and direct
transmission paths the direct path was always the dominant one.

This is for a normal partition not where we are dealing with some sort
of specalist acoustic construction such as a TV or movie studio

Please don't take my comments the wrong way, I got some of my first
pointers doing my undergrad thesis (~1997) from one our your replies
to a message so many thanks.

Tom

[sergioTOOL]

Thanks a lot guys