A decibel (dB) is the unit of measurement for sound intensity. Broadly, there are two types of sounds within a building:
(i) Airborne Sounds, whichare sounds transmitted though air, such as voices or
radio playing, and (ii) Impact Sounds, which are created by an impact of an object with building
elements or furnishings, such as footsteps, dropped objects, toys, furniture
scraps, piping, and some appliance sounds.
A 10 decibel increase means the sound is ten times louder. Prolonged
exposure to noise louder than 85 decibels can impair hearing
Very painful
160
Shotgun
Painful
140
Stock car race
130
Jackhammer
Deafening
120
Rock concert
100
Chainsaw
Very loud
90
Hair dryer
80
Police whistle
Loud
70
Average radio
60
Normal conversation
Moderate
50
Average Office
40
Quiet radio
Faint
30
Whisper
20
Rustling leaves
Very faint
10
Soundproof room
0
STC:
Sound Transmission Class. A laboratory measurement of the ability of
walls and floors to mitigate airborne sounds including voice, television and
alarm clocks.
NIC:
Noise
Isolation Class. An over-all measure of the sound isolation between
units in a multi-family dwelling. A field measurement of the ability
floor/ceiling assembly to mitigate airborne sounds.
IIC:
Impact
Insulation Class. A laboratory measurement of the ability of proposed
materials to mitigate against impact sounds such as footfalls.
FIIC:
Field
Impact Insulation Class. A field measurement, i.e., done after a
hardwood floor
installation is completed to test actual noise transmission into the unit
below.
The
higher the value, the greater the noise isolation. For
example, an STC of 52 provides better sound protection than an STC of 45. Building codes
typically require that floors provide an airborne sound insulation to meet
an STC of 45 (field-tested) and an IIC of 45 (field tested) for impact noise.
See California
Building Code for
more information. Note: local codes may require higher standards.
