Noise Control Basics

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Noise Control Basics
QuietZoneR Acoustic Batt
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Architectural Acoustics

• The study and design application of everything
  which involves hearing in or around buildings.

Goal of Acoustics
To make sure that each occupied space is
acoustically designed to best serve the function
intended.
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Sound Definition
Sound (sound) n. An audible signal transmitted
from a vibrating source to a receiver through the
air as a differential in atmospheric pressure.
It is this differential in atmospheric pressure
that allows our ears to hear the sound. A
greater pressure difference a louder sound
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Loudness and Decibels
Loudness is measured on the decibel scale. A
decibel is a relationship between 2 values of
power. When the powers differ by 10, that equals
1 bel. A decibel is 1/10 of a bel. Therefore
10x log (Power A/Power B) dB eg. 101
relationship 10xlog10 10 db 21
relationship 10xlog 2 3 db
A 10 fold increase in power will increase the
sound by 10 dB (effectively doubling sound)
A doubling of power will increase the sound by 3
dB
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Decibels cont.
The decibel scale is a reflection of the
logarithmic response of the human ear to changes
in sound intensity. 0 dB threshold of
hearing 1 dB smallest change in sound 3
dB noticeable change in sound 6 dB very
noticeable difference 10 dB double the
loudness 120 dB threshold of pain
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Different Sound Levels of Various Sources
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Frequency of Sound
Hz hertz, the unit of frequency (cycles per
second)

• Music

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Frequency of Sound
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Two Types of Sound Transmission

• Structure borne sound
• Vibrations transmitted through solid structures
  
• Airborne sound
• Sound transmitted through the air as a
  differential in air pressure

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Sound Transmission Loss

• The reduction in sound pressure level measured in
  decibels as sound energy passes through a
  material or composite construction.
• i.e. through a wall, floor, door or window
  partition

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Sound Transmission Classification (STC)

• A single number rating based on sound
  transmission loss measurements of a partition
  between adjacent closed rooms

STC contours are heavily weighted in the low
frequency regions by a reduction of 3dB per 1/3
octave from 400 to 125 Hertz.
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STC Noise Reductions
A conventional wall (2x4 with one layer gypsum on
both sides) has a STC rating of 35. The
following table indicates the approximate
increase in the perceived noise level as a walls
STC rating increases.
QuietZone Acoustic Wall Framing increases noise
control performance ratings by 14 to 28 STC
points over conventional wall constructions.
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STC Summary

• STC is a sort of composite attenuation.
• The larger the STC, the better the attenuation.
• National Building Codes typically require an STC
  of 50 or more.
• STC 55 satisfies more people and is not difficult
  to achieve in laboratory tests.
• In practice, good sound isolation requires
  attention to details.