22 interiors+sources july2018 interiorsandsources.com
the second is scientific, and easy to quantify. Both are very
important. Together, they make up the lion’s share of all
Acoustic signature is the unique quality of how something sounds; how we like or dislike a sound. “I like her
voice,” or “What a beautiful song,” are purely subjective,
yet extremely important statements. The uniquely identifiable
aspect of a sound is like a fingerprint or signature (hence
the term acoustic signature). Acoustical design is the
craft of creating a specific acoustic signature for a room.
Sometimes referred to as studio design, it can apply to any
space where a specific acoustical experience is desired.
Acoustic isolation is being able to keep sounds from
moving between spaces or through walls, ceiling, and
floors. Historically, it has been the most complex, laborious,
and expensive part of acoustics because of the challenges
of how easily low frequencies transfer through walls. We
traditionally see acoustics using mass and density to create
The newest technology in acoustics—quantum acoustic solutions—are in the preliminary stages with estimated
performance as high or better than traditional solutions with
increased low frequency performance at a fraction of the size,
saving many square feet while increasing the overall volume of
the room. Now that quantum acoustics has solved the age-old challenges of acoustic signature design, one can expect
to see new designs, applications, and products based in
quantum acoustics for acoustic isolation uses.
To put this technology into use, it's important to understand what different ratings and terms mean.
Decibel (dB): A logarithmic ratio unit of measure which is
one-tenth of one bel. There are weightings or filters that
adapt the dB for different uses, such as human hearing.
These weightings are designated by a one of five letters after
the symbol: A, B, C, D, or Z. For example, dB A is equalized
to mimic human hearing whereas dB Z is un-weighted, raw
measurement. Basically, higher dB equals louder sound and
because it’s logarithmic, twice the dB can be much louder
than twice the number.
Acoustic resolution is a real world unit of measure for
acoustical performance, denoted by NPS/ft2 . Acoustical
resolution is directly related to acoustical performance:
higher resolution values result in higher acoustical performance. More (higher number) NPS/ft2 means better
sound: this includes better imaging, greater clarity, better
definition, increased intelligibility, and larger sweet spots.
Like physics and nature, there is no upper limit to acoustic
resolution; it is only limited by the technology of the time
and materials science.
One “Sabin” is one unit of sound absorption. If you want
to absorb all sound, get a material rated for 1 sabin, which
is the maximum rating. Minimum is 0 sabins, with ratings
being in 0.1 increments; 0.1, 0.2, 0.3 up to 0.9, and 1.0.
• Max absorption = 1.0 sabin
• Min absorption = 0.1 sabin
• No absorption = 0.0 sabin
However, this is can be tricky as sometimes it means
100-percent absorption at a particular frequency, not all
frequencies. Sometimes manufacturers will claim 100-per-
cent sound absorption or 1.0 sabin, but in the fine print
they’ll say it’s only at limited frequencies; much less than
the full range we can hear. While it’s legally correct, it’s not
in the spirit of the unit of measure and less than helpful
Outdoor-Indoor Transmission (OITC) is a measure of sound
isolation between outdoor and indoor spaces with more
emphasis given toward the lower band of audible frequencies. In short, it’s used to measure sound getting into living
spaces or offices where the exterior is loud.
Noise Reduction Coefficient (NRC) is basically a rating for
sound absorption, much like the sabin, only with a very limited
range. The American Society for Testing and Materials
(ASTM) has standardized testing procedures to measure
NRC including frequencies from 100 hz to 5000 hz. (Note:
human hearing range is from 20 hz to 20,000 hz.) It is most
commonly used for ceiling tiles and other wall or ceiling
mounted acoustical absorbers.
Sound Transmission Class (STC) tells you how much a wall,
ceiling, floor, door, or partition isolates sound from one side
to the other. It is mostly used for interior spaces, but there
are test procedures for exterior uses as well. Like NRC, it
covers less than 25 percent of the human hearing range. If
a wall is rated for 22 STC it means that 22 db of sound is
prevented from getting through that wall. It’s a widely used,
moderately effective unit of measure due to its limited
Impact Insulation Class (IIC) measures the sound of footsteps between floors in a building. As spaces get easier to
build with minimal structure, the sound of people walking
has become a significant sound isolation issue in multi-story
buildings. This is an important aspect and one that everyone has to deal with.
For a more in-depth look at acoustics, the unedited
version can be found at www.interiorsandsources.com.