HSW/STC SOUND ENVIRONMENT LEARNING AND HEALING › FAC7232F-1B5...• Excessive noise can induce...
Transcript of HSW/STC SOUND ENVIRONMENT LEARNING AND HEALING › FAC7232F-1B5...• Excessive noise can induce...
HSW/STC
SOUND ENVIRONMENT
LEARNING AND HEALING
BY:
United Plastics Corporation
511 Hay Street
Mount Airy, NC 27030
(800) 577-3931
www.dbsoundcontrol.com
Upon completion of this course, you will have a better understanding of:
•What is Noise
•How does it effect us, what’s it’s affect on Healthcare, Education and Quality of Life?
•dB and Frequency scales
•Acoustical treatments per frequency range
•Transmission Loss Tests and how to read the data
•STC: Sound Transmission Class
•STC of various wall assemblies
•Acoustical value of Wood versus metal studs
•Value of stud spacing (16” versus 24” on-center spacing)
•Value of sustainable acoustical barriers
•Value of batt insulation
•Multiple layers of drywall
•Best Practices to meet desired STC targets
•Cost Comparison of wall assemblies
•Making it simple: Design criteria
Learning Objectives
Noise is simply ‘unwanted sound’
noise n. 1. a. Sound or a sound that is loud, unpleasant, unexpected, or undesired.
•NOISE IS… Televisions on while you are trying to sleep
•NOISE IS… Neighbors talking in the adjacent apartment
•NOISE IS… Washers / Dryers running while trying to watch TV
•NOISE IS… Not being able to concentrate in a loud workplace
•NOISE IS… People walking on the floor above your apartment
Noise do not have to be LOUD to be an annoyance
It just have to be louder than any other noise in the surroundings.
Definition of Noise
The number one complaint with all US law enforcement is NOISE
•The decibel (dB) is commonly used in acoustics to quantify sound
pressure levels relative to some 0 dB reference.
•0 dB is the reference point where the eardrum no longer vibrates
and sound is not heard.
•dB scales allow one to use a logarithmic rather than a linear scale.
It has the distinct advantage of allowing one to do calculations within
a scale of small numbers rather than over an extremely large scale of
numbers.
What is a decibel (dB)?
It is important to understand what the dB scale is and what the levels mean. One does not
need to achieve 0 dB in a room to eliminate Noise.
The dB Scale
0 dB – Threshold of hearing (eardrum
begins to detect vibrations)
140 dB – Apollo Rocket
90 dB – Loud manufacturing environment (ear
protection is required – limited exposure OSHA)
60 dB – Car interior while driving
50 dB – People Talking
40 dB – Ambient Noise (outside during the
night with limited background noise)
Goal: To achieve Sound
Pressure Levels (dB)
below 40 dB (which for
many environments, will be
void of any ‘noise’ issues).
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Noise Levels In Education
• Cognitive development is impaired when homes or schools are near
sources of noise such as highways and airports.
• Noise affects learning, reading, problem solving, motivation, school
performance, and social and emotional development.
• Children who live in noisy environments have been shown to have elevated
blood pressures and elevated levels of stress-induced hormones.
American National Standards Institute calls for a
maximum ambient noise level of 35 dB
Noise Levels In Healthcare
Excessive noise, and its effect on rest, are high on the list of complaints made by
patients on post-discharge patient satisfaction surveys.
• Excessive noise can induce headaches, cause irritability, prolong wound
healing and increase sensitivity to pain.
• Noise levels in hospitals are twice what they were a few decades ago.
• Sound levels inside hospitals average 72 decibels during the day and 60
decibels at night
WHO standard, for night time ambient sound
is 40 decibels
In 1859 book Florence Nightingale called noise "the most cruel absence of care."
Adding and Subtracting dB’s
If one was to DOUBLE the Sound Pressure Levels,
how many dB increase is this?
If one wanted to reduce the noise levels by 50%,
how many dB decrease is this?
70 dB
The Rule of 3 dB
70 dB
When you DOUBLE the noise levels (two speakers in this
instance), the sound pressure levels increase by 3dB
73 dB70 dB + 70 dB = 73 dB
For you math experts out there, the
logarithmic sum of doubling a noise
source is:
dB=10*log(2) = 3dB
Double the volume
The Rule of 3 dB
Therefore, when designing a wall system – or trying to reduce noise levels, a
3dB reduction is the same as turning down the volume knob 50%.
3dB decrease (or increase) = 50% reduction in sound pressure levels
6dB decrease (or increase) = 75% reduction in sound pressure levels
9dB decrease (or increase) = 87.5% reduction in sound pressure levels
And so on…
Frequency is simply ‘number of cycles per time interval’, or to better visualize,
how many times your eardrum moves back and forth per second (cycles /
second).
• At 100 Hz, the eardrum moves back and forth 100 times / second
• At 5000 Hz, the eardrum moves back and forth 5,000 times / second
•The human ear responds to a range of frequencies from approximately 20 to
16,000 Hz.
•The human speech range is approximately between 400Hz and 4kHz.
Frequency (Hz)
400Hz 4kHz
Human speech range
The Frequency Scale (Hz)
Low Frequency
•Boom Noise
•Bass
Mid Frequency
•Speech Noise
•Television / Radio
High Frequency
•Siren Noise
•Birds chirping
63 Hz – 315 Hz 400 Hz – 4kHz 4 kHz – 10kHz
The frequency scale is broken up into three distinct regions (low, mid and
high). This is important because each frequency region has different
acoustic treatments associated with reducing their sound pressure levels.
The Frequency Scale (Hz)
Low Frequency
•Treat with Isolation
techniques. (Like a
spring or an ‘isolator’)
Mid Frequency
•Treat with mass layers
to block and reflect the
noise
High Frequency
•Treat with absorption
63 Hz – 250 Hz 400 Hz – 4kHz 4kHz – 10kHz
Frequency range and corresponding acoustical treatments
•Low frequencies are reduced via isolation techniques
•Higher frequencies are reduced via mass and absorption techniques
Low-frequencies are the most difficult to treat (< 250 Hz). Wavelengths are very large and these
frequencies carry a lot of energy and drive entire wall systems.
Best way to treat (reduce) low-frequencies is to make two separate wall assemblies and ‘isolate’ the
transfer of energy from one wall to another.
Low Frequency: Isolation
(< 250 Hz)
The “Goal” is to eliminate the transfer of vibration
from one side of the wall to the other. For very loud
source rooms (home theaters, for instance), a second
wall assembly NOT mechanically attached in any way
to the adjacent wall assembly is a preferred method.
Other methods: Reduce the number of studs (24” on-
center spacing instead of 16”) or to significantly
increase the mass of the entire wall assembly.
Best Practices to reduce low-frequency noise: 1. Add another wall assembly
2. use fewer studs
3. Add Mass
This frequency range where most speech occurs is from approximately 400Hz to 4kHz. This mid-
frequency range is best treated with MASS of the wall system.
The more mass that is added, the less noise is transmitted out the other side.
Rule of thumb: For every doubling of mass, the sound pressure levels are reduced by 6 dB throughout the spectrum.
Mid- Frequency: Mass-controlled region
(250Hz – 2 kHz)
60 dB
Best Practices to reduce mid-frequency noise: 1. Double the Mass: Reduce levels by 6 dB
2. Add absorption
3. Use Isolation
20 dB 60 dB
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ass
14 dB (6 dB less)
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example
In the higher frequency range, wavelengths are short and are more easily reflected back off of rigid wall
systems. Recall that noise travels back and forth approximately 94 times a second in a 12’ X 12’ room
environment. Thus, absorption would have 94 chances to absorb the echo within the room every
second.
If the noise (frequencies) is not going through the wall, then it is being reflected back (echo). Add
absorptive layers throughout the environment to absorb these reflections and minimize the echo in the
room.
High Frequency: Absorption Controlled region
(> 2 kHz)
Best Practices to reduce high-frequency noise:
1. Add absorption (treat the room where the noise resides and not necessarily the wall)
Incoming
noise
Difference between
incoming noise and
reflected noise = absorption
of the product. Reflected
noise
Absorptive
Fiber
DIFFERENT TREATMENTS / METHODOLOGIES ARE USED TO TREAT
DIFFERENT PARTS OF THE FREQUENCY RANGE:
Chapter 2 Summary: What we have learned thus far
Low Frequency: Best reduced via isolation techniques
Mid-Frequency: Best reduced via mass of the wall system.
High-Frequency: Best reduced via absorption within the room environment itself.
Sound Transmission Class
• STC is a SINGLE-NUMBER CLASSIFICATION used to rate the transmission
loss of a wall.
• The higher the STC value, the more efficient the wall is in reducing sound
transmission.
STC = 34
Transmission Loss Graph: What it means
5/8” drywall on both sides of wall
STC
Assigning a single number to a wide spectrum of frequencies often
times does not tell the entire story – it is best to look at the entire
frequency range and determine the best practices to reduce noise
with the appropriate wall system.
The more noise the wall system reduces – the higher the STC
number.
Compare Transmission loss and STC values of
various wall assemblies.
•Metal versus Wood Studs
•Acoustical Barrier
•Batt insulation
•Spacing of studs (16” versus 24”)
Here is the TL performance of both metal and wood studs
Metal studs perform approximately 6dB to 10 dB better wood studs throughout the spectrum. This is
significant!
5/8” drywall on both sides of wall
Comments:
Metal studs perform significantly
better than wood studs!
Wood: STC = 34
Steel: STC = 39
Why are metal studs better at reducing noise as compared to wood studs?
Metal versus wood studs
wood metal
Vibration (noise)
going into the
wood studs
Does not get
‘absorbed’ in the
wood stud…
too rigid and stiff
And transfers
much of the
original vibration
out the other side
1
2
3
Vibration (noise)
going into the
metal studs
However, the
thickness of the
metal stud is only
~ 1mm thick and
‘absorbs’ like a
spring
Only a small
percentage of
vibration is
transmitted out
the other side.
1
2
3
Metal studs transfer much less energy than wood studs
Less vibration = Less Noise
Influences of stud spacing: 16” versus 24”
There are no consistent trends in performance between 16” or 24” spacing
24” spacing offers improved low-frequency performance while 16” on-center improves mid to high
frequencies slightly. Since lower frequencies are most difficult to treat, the 24” on-center spacing is
recommended as the best design for reducing noise.
16”: STC = 39
24”: STC = 40
Comments:
24” on-center
An Acoustical Barrier has the following traits:
Heavy and dense, yet limp so it does not radiate vibration easily
Thin profile (usually ~ 2mm thick)
Flexible to wrap around corners
Impermeable to moisture
Sustainable, recyclable good for the environment
The addition of a 1 lb/ft2 acoustical barrier placed behind the drywall offers ~ 5 dB improvement (reduction) in performance
throughout the spectrum. This is significant!
Influence of adding ONE Acoustic Barrier layer
With one layer of
acoustic barrier
w/o: STC = 34
With: STC = 37
Comments:
Baseline Wall system
– no barrier
Influences of an Acoustical Barrier Layer
Conclusion
Acoustical Barrier Layers:
1. Reduce Sound Pressure Levels ~ 5dB per Layer
2. Increase STC ratings ~ 3 to 4 points per layer
3. Reducing Sound Pressure Levels increases wellness, alertness and
better productivity.
The combination of a batt insulation AND an Acoustical Barrier Layer reduces sound pressure levels ~ 10 dB throughout
most of the frequency spectrum.
Influences of an Acoustical Barrier Layer with
and without Batt Insulation
None: STC = 34
Barrier (1-Layer): STC = 37
w/ batt insulation: STC = 41
Comments:
1-layer of barrier WITH
batt insulation
Approximately 10 dB reduction in Sound Pressure Levels occur with a single layer of acoustical barrier - plus batt insulation
Approximately 16 dB reduction in Sound Pressure Levels occur with a layer of acoustical barrier on EACH side of the wall -
plus batt insulation
None: STC = 34
Barrier (1-layer) STC = 37
Barrier / Batt (1-Layer): STC = 41
Barrier / Batt (2-Layers): STC = 43
Comments:
2-layers of acoustical
barrier with batt insulation
Influences of one versus two layers of
Acoustic Barrier - with Batt Insulation
A wall system that utilizes a single layer of Acoustical Barrier PLUS batt insulation performs better than two-layers of barrier
without insulation.
Barrier (2-layers): STC = 39
Barrier & Batt Ins.: STC = 41
Comments:
Barrier with Insulation
performs better
Two layers of Acoustical Barrier (No Insulation)
Versus One-layer with batt insulation
2-layers of acoustical
barrier only (no insulation)
Conclusion
What is better acoustically: 2-layers of Acoustical Barrier or a
single layer of acoustical barrier with Batt Insulation?
1. A single layer of acoustical barrier plus batt insulation
reduces Sound Pressure Levels ~ 3 to 5dB throughout
most of the frequency spectrum as compared to a wall
system with just two layers of acoustical barrier.
2. STC points are increased approximately 2 points with the
batt insulation
Two layers of Acoustical Barrier (No Insulation)
Versus One-layer with batt insulation
Lets take what we have learned thus far…and create a
STC Wall system that achieves levels greater than
50….and greater than 60.
1. Start with a wood stud wall system (worst case) with
no treatments
2. Change to metal studs
3. Add Acoustical Barrier plus Batt insulation
4. Increase stud spacing to 24” on-center
5. And finally, add another barrier layer for a total of 2
barrier layers in the system
Learning exercise
2-layers of drywall, 2-layers of
barrier, batt insulation
Baseline STC = 34
Metal Studs STC = 39
Metal Studs with Acoustical Barrier & Batt Insulation STC = 52
Metal Studs (24” on-center) / barrier / Batt Insulation STC = 56
Metal Studs (24” on-center) / 2 layers drywall / 2 layers of barrier / batt insulation STC = 62
Add another layer of Acoustical Barrier
This chapter looks at other wall designs commonly found in the industry and
compares them to the acoustical barrier wall assembly.
•2-layers of 5/8” drywall (both sides of the wall)
•Damped drywall
Chapter 6 – Alternative Wall designs
2-Layers of 5/8” drywall (both sides) Versus Single Layer 5/8” drywall,
Acoustical Barrier & Batt insulation
Two layers of drywall STC = 50
The wall system utilizing acoustical barrier performs significantly better than 4-
total layers of 5/8” drywall.
2-layers of 5/8”
drywall (both sides)
5/8” drywall on both sides of wall
Acoustical Barrier w/ batt insulation versus ‘damped’ drywall w/ insulation
Damped
drywall
Summary
The Acoustical Barrier wall assembly has higher (better)
measured transmission loss performance as compared to:
•Multiple layers of drywall (two layers per side)
•Damped drywall (with batt insulation)
Why?
Summary
Because:
• As previously mentioned the transmission loss in the mid-
frequency range was best treated with ‘mass’. However, that is
only half of the story.
• The remaining variable is STIFFNESS of the wall assembly – or
more importantly, the ability of a wall to radiate noise efficiently.
(radiation efficiency).
• Drywall is inherently stiff. Recall as a child and taking a glass jar
to the drywall to hear the noise on the other side of the wall. You
hear the noise on the other side of the wall so well because
drywall is stiff and radiates noise very efficiently.
Cost analysis of each system
This section examine the cost structure of the most common
types of wall assemblies:
1. Acoustical barrier with batt insulation
2. Damped drywall with batt insulation
3. 2-layers of drywall (both sides)
Cost analysis of each system
Drywall Description1 layer of 5/8"
dryw all both
sides
1 layer of 5/8"
dryw all both
sides
2 layers of 5/8"
dryw all both
sides
2 layers of 1/2"
dryw all on one
side, 5/8" dryw all
on other side.
1layer of 5/8"
dryw all both
sides
1 Layer of 5/8"
dryw all both
sides
1 layer damped
dryw all 1side,
5/8" on other side
Full Wall Systems Construction
Costs Comparisons
Baseline
Wall System
(Single 5/8"
on both
sides)
dB-3 ®
PRO (1 side)
dB-3 ®
PRO (both sides)
Green Glue
Assembly 1
layer
Resilient
Channel
Assembly
Isolation Clips
with Furring
Channel
Damped
Drywall
S T C 3 9 5 6 6 2 5 2 5 5 5 9 5 5
Drywall materials $64.00 $64.00 $128.00 $84.00 $64.00 $64.00 $247.00
Drywall, labor $36.00 $36.00 $72.00 $48.00 $36.00 $36.00 $88.00
Total cost materials + labor $360.86 $650.57 $999.45 $677.74 $595.11 $846.68 $866.52
Cost per Square Foot $3.61 $6.51 $9.99 $6.78 $5.95 $8.47 $8.67
STC values based on published reports: 25 gage metal framing wall system, 24" on-center, 10'x 10' wall assemblies
Building the correct room
First thing to do is take care of the rooms themselves with
ABSORPTION.
Add draperies
Add plants
Add acoustical panels
Add carpeting
Noise WILL get into the rooms – either through adjacent
walls, windows, doors, ceilings…from anywhere and
everywhere.
Absorptive treatments are an easy way to combat these
noise levels and capture (reduce) the reverberation as it is
bouncing back and forth ~ 94 times per second.
ABSORPTION is key
Chapter 7
Building the correct room
Proper design and acoustical performance can be achieved if
these simple guidelines are followed:
Isolation
Mass
Radiation efficiency
Absorption
Failure to implement any ONE of these variables into your design
will significantly degrade the overall performance of the system –
and sound quality will be compromised.
Low-frequency
Mid-Frequency
High-Frequency
Course Summary
A wall assembly utilizing acoustical barrier:
1. Achieves higher STC values as compared to other popular wall assemblies
• Due to the heavy mass of the acoustical barrier
• Due to the low radiation efficiency of the acoustical barrier
2. Is up to 25% lower in overall cost when compared to damped drywall
assemblies of similar STC values
3. Using an acoustic barrier will add to the overall performance of the building
without extra expense.
2. Acoustic Barriers: Save Money, they not only act as noise
barriers, but moisture and insulation barriers as well.
3. Using sustainable products protects the environment for future
generations
4. An acoustic barrier is completely recyclable.
www.dbsoundcontrol.com