Environments for Aging - Spring 2015 - 22

CONSTRUCTION

Sound without fury
Managing resident expectations for acoustics in senior living environments is important, but so is
managing the noise itself by building to code and not skimping where it counts By James Mehaffey
about 50-54 STC (as measured
Building codes provide a reasonable
in a laboratory), the wall must
level of safety and occupant comfort.
have two layers of wallboard on
For example, buildings are never
one side of the studs, the stud
fireproof, but they're built to provide
cavity filled with fiberglass insulaa practical fire buffer. The same
tion, and another layer fastened
can be said of acoustics. Although
with resilient metal clips to offset
never soundproof, buildings must
the board from the stud by
meet International Building Code
one-half inch. These clips allow
standards for noise transfer between
one side of the wall to vibrate
residences.
James Mehaffey
independently from the other,
Some noise should be expected
so the noise energy doesn't translate from one
in a multifamily living arrangement, though,
side of the clip to the other at 100 percent.
and the code recognizes this. However, some
This example wall is, in effect, 50 percent
incoming residents to senior living communimore dense than the standard wall. Building
ties might not expect that. Instead, they'll likely
codes also require that all openings, cracks, and
anticipate the same quiet environment they've
seams be sealed with acoustical caulk and that
experienced in a single-family home. Children
penetrations, such as electrical outlets, be staghave long since moved out, and prospective
gered between studs to avoid having two across
residents may even live alone. The only sounds
from each other within the same cavity opening.
they hear are their own.
So overall, code calls for the standard wall
Rarely will anyone explain to residents enterto be about 15 to 20 STC points higher than
ing a new community the reality of what they
it would have been. That seems pretty good,
might hear from their neighbors, but expecbut how good? A rule of thumb is that for every
tations should be better managed in order
10 STC you add to an assembly, the sound
not to disappoint new move-ins. The walls,
coming to the other side is roughly half as loud.
ceilings, and floors between units will never be
So an added STC of 15-20 will roughly slash
soundproof, but buildings can be constructed
airborne noise by one-third or one-quarter, but
to manage noise at an acceptable level.
doesn't eliminate it altogether.
Floors will be very similar to walls, except a
The basics
typical assembly "sandwich" would be made
Current building codes address both airborne
up of wood joists and fiberglass insulation
and structure-borne sound. Simply stated,
topped with plywood subfloor and gypsum
airborne means hearing your neighbor's voice
poured topping. The bottom would have severor TV, and structure-borne is hearing your
al layers of wallboard attached to metal clips on
neighbor's footfalls above you or their garage
the underside of the joists. A floor needs to perdoor open.
form well with structure-borne noise, too, such
To address airborne sound in particular, the
as footfalls. Typically, this is addressed with an
wall, floor, and ceiling assemblies between
acoustical mat placed between the gypsum
dwellings must meet a sound transmission
topping and the plywood in the assembly to
class (STC) of 50 to reduce transfer from one
provide additional resilience. The mats can also
side of the wall to the other, a level that far exbe placed right below flooring.
ceeds standard wall construction found in older
building stock or in a single-family home. STC
ratings are a fairly sensible predictor of how
a wall will perform and use a range of 125 to
4,000 hertz, which is the range of frequencies
associated with human speech.
A wood stud wall with a layer of wallboard on
either side has an STC of about 34. To get to
22

EFAmagazine.com * Spring 2016

Adding and subtracting
When considering going beyond code, it's
important to measure diminishing returns.
For example, 5 STC is clearly noticeable,
3 STC is just barely perceptible, and 1 STC
is almost imperceptible. Mass is important to

acoustical performance, so if the thickness of
a membrane is two layers of wallboard instead
of one, the STC rating will increase by about 5.
Installing insulation in a wall also adds about
5 STC. An STC of 60 is considered a "luxury"
level, but even then some loud noises will be
heard faintly through the walls.
Although wood construction is most often
used in residential settings, metal studs perform a bit better due to their flexible characteristics, as they can soften or decouple some of
the noise vibrations from one side of a wall to
another. Additional considerations in acoustical dissipation include mass and airspace
between. Any time two or more of these properties can be added to an assembly, improvements will be realized.
During pricing exercises on a project, designers and owners often must collaborate to
make concessions and reduce costs. Some of
those decisions may affect acoustical comfort,
including replacing cast iron waste pipes with
PVC pipes, reducing or changing types of
insulation on pipes, providing alternate wall
assemblies or alternate finishes that may be
less absorptive of sound, or choosing HVAC
and mechanical items that perform worse
acoustically. All of these choices can degrade
the acoustical comfort present in a building
during its initial design, so it's important to note
the added cost of addressing acoustical issues
after construction is complete and adequately
weigh the ramifications of those decisions.

Peace and quiet
Prospective residents should always be alerted
that their future home won't be soundproof,
even in new construction. Whether they're
moving into an apartment or semi-detached
unit, it's often a new type of home for them,
so differences between single-home and
community living should be outlined. In most
cases, adhering to the building standards
above and managing expectations will provide
acoustical comfort and satisfaction. EFA
James Mehaffey is senior project manager at RLPS
Architects (Lancaster, Pa.). He can be reached at
jmehaffey@rlps.com.

http://www.EFAmagazine.com

Environments for Aging - Spring 2015

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