|
STC |
What can be heard |
|
25 |
Normal speech can be understood quite easily and
distinctly through wall |
|
30 |
Loud speech can be understood fairly well, normal
speech heard but not understood |
|
35 |
Loud speech audible but not intelligible |
|
40 |
Onset of "privacy" |
|
42 |
Loud speech audible as a murmur |
|
45 |
Loud speech not audible; 90% of statistical population
not annoyed |
|
50 |
Very loud sounds such as musical instruments or a
stereo can be faintly heard; 99% of population not annoyed. |
|
60+ |
Superior soundproofing; most sounds inaudible |
The use of mass loaded vinyl will attenuate frequencies
that will not be controlled by wall treatments.
The demanding reference standard (a
guideline for high-quality audio in movie soundtracks) requires partitions to
achieve 50dB of attenuation at 63 Hz.
If an 80dB sound on one side of a
wall/floor/ceiling is reduced to 50dB on the other side, that partition is said
to have an STC of 30
wall with an STC of 30 may provide over
40dB of attenuation at 3000 Hz but only 10dB of attenuation at 125 Hz
The "Noise Reduction Coefficient" (NRC) is a measure of how
much sound is absorbed by a particular material, and is derived from the
measured Sound Absorption Coefficients